and young colleagues. It's a pleasure to be with you today. Okay, it's a pleasure to be with you. It's always a pleasure to be with you. And there aren't too many at this great Moran Eye Center do anything with contact lenses who are MDs. You see one of them right here in Kim Taylor's, the other. And let's just talk about it. And I'd like to have you after this hour or even a little less with the paper that I'm handing out and what you'll see and what I'll tell you here able to go into contact lens fitting and do a pretty good job of it because it's just chancey right now. You just sort of you get one like you saw somebody else get one and sort of put it on somebody and let's make it a little better than that. A little bit of general information. When you think about contact lenses, maybe the first ones are what they call scleral contact lenses. Those were used in care to conus and they were glass lenses. They called them scleral because they fit on over the wide of the eye. Of course, they fit on the conjunctivus of sclerals have done name but anyway, they were big.  Maybe normal saline, they get this bucket of normal saline in this lens. It's a lens of power and they sort of figured out what might work and for starters, maybe it's a trial lens and they'd bend over and put it on the eye and the care to conus patients were thrilled to have something help. I talked to a friend who said one of the early stockbrokers to come to this part of the country and maybe he wasn't a stockbroker. He was doing that and was with the old Edward L. Burton company. He'd come to the office and he'd read the financial page. You want to know how he read the financial page? He read the financial page like this. He had the paper right on his nose and his forehead and that's the only way that somehow cut it. Nobody told me what he had but I didn't have to be told. He had care to conus. I think care to conus came to the inner mountain west with those early fine there as they brought it. Are you aware that we have more care to conus here than elsewhere generally? Have you heard about that? I was talking to an ophthalmologist in Florida once. He said, boy, you sure have a lot of care to conus there. I thought, well, that's interesting and I didn't think too much about it and then Claes Dolman was giving a talk and one of the resorts around here and we had him here for a visiting instructor and he was talking about his main subject and he said, well, by the way, let's talk about care to conus for a while. He showed the operated care to conus when corneal transplant was the thing done. One thing got out of control and you couldn't see well with contact lenses anymore. He showed all the surgery at Massachusetts Eye and Ear Infirmary. I just sat and watched and I thought, Joe Hatch is doing more corneal transplants than the Massachusetts Eye and Ear Infirmary. Either I'm a crazed surgeon or we've got a lot of care to conus and I submit to you that I think it's the latter and so it's interesting stuff but beyond that kind of lens, it gave people a little help for an hour or two. The next one was polymethylethacrylate and that's a plastic lens. Everything's made out of these days, mostly inside of your car. That's polymethylethacrylate. That lens didn't breathe. No gas exchange through it. You had to blink and oxygen in the tears to get to the corneal and you do pretty good and they weren't bad. They were around for a long time. They may have started, I don't know, maybe in the 1940s. There certainly wasn't a lot of use before then with that type of lens. A big uptake was when the rigid gas permeable lenses came along and that's polymethylmethacrylate plus silicone.  It wouldn't be good for anything but by golly it was a material that could be clear and you could cut a lens and it still works very well for hammered corneas and keratoconus, things like that and the soft contact lenses. Of course, these lenses show us for most of the general optical improvement type of contact lenses. Physicians haven't been fitting contacts for a long time. When I took my oral boards, the examiner looked me in the eye and he said, okay, how about a minus 1.75 mile in each eye comes in, says she wants contact lenses. What are you going to do? Well, I said as well, I think maybe I'd see if she liked glasses in a nice, attractive frame. They're kind of sexy. Maybe that would work out pretty good. He said what if she said I want contacts and I don't want anything else, then what would you do? I said I'd fit her with contact lenses and he looked alarmed when he looked back at me. Like you're going to compromise your standards or something? Well, it wasn't my standard. I was fitting some contact lenses and I thought well, there's always next year I'll try the oral boards again, but happily he didn't swing enough weight to bury me. That's how some of this is. A few things about contact lenses. On the rigid ones, I tell people once they're well set with a rigid lens to get a spare pair, always have a spare pair. If you lose or break one lens, replace it and get a new replacement so you still have a spare pair because there's nothing more disenchanting.  Well, take it from me. Those lenses are probably warped and scratched and they're a mess and you're not going to find anything there that will answer it. If they come into me and don't have any contact lenses at all in their possession, but I know what their last prescription was, I simply order the last prescription and treat them as trial lenses, get them in. Well, I think Moran orders out of Minnesota. I think that's where the ones that I would get at Mid Valley would come from. When they come in, I do a spherical over refraction and if they see well and it's fine, that's good. If not, I find out what power I want to order and order that and then tell them to get a spare pair exactly like this or if I'm only changing one, get another one like this. I say throw away every contact lens you have because these people scroll away contact lenses all over the place. They're stocking drawer and they're everywhere. So you get rid of every one and they'll save you a lot of grief. A few other little details that are kind of important. Some kind of lenses might be time consuming or somebody goes to Google and they find this super special lens for character quality. This is the one I want. Well, if you're not fitting lots of contact lenses, really making your way of life, you might want to refer that one off to your colleague who does find somebody who will handle it because a lot of those lenses, when they come in, they cost $100, $150, $200 per lens and you bought it once you get there. It's not a trial lens. It's yours and if you can't use it, it's yours for junk. So you might want to send certain things off and that's quite all right and it's good. I think it's wise to choose your fee. Tell the patients this will do for three months. If you have to come back a time or two, we'll of course take care of it. We'll do re-evaluations as necessary and exchange trial lenses and they like that too. They like to know what's going on. There are a lot of different contact lens solutions. These are Boston solutions. That's one of the good ones. By the way, I have a handout here. I advise you to be sure you get one and if you don't get one at the end of the talk, these are Boston solutions. This is the old kind. It has a cleaner and a wetting solution. The problem with that is sometimes people mix up with two and they use the cleaner and then they put it in their eye and that is an owie immediately and it is just terrible. So Boston, they call it Simplis, S-I-M-P-L-U-S. It's Simplis because there's only one and it does whatever cleaning it might do but it also is a wetting solution. There are so many kinds and they will usually provide starter kits. I've won this Boston Lohman once at Alcon for soft contact lenses. There are a lot of solutions and my advice on solutions is to get a kind you like and stick with it unless you feel that it's irritating your eye or giving you a problem and okay, go ahead and make a change but make it too complicated. Okay, we talked about the, when I fit rigid gas permeable lenses, I only fit spherical lenses. I never do a back-torque. I never have and I haven't had any trouble. I have so many patients who do so well. That rigid back-torque, a lot of special treatments on making rigid contact lenses that you sort of have to crimp the lens or do other things. I want to lens so that patients say this is the most wonderful lens I've ever had in my life. I sure hope I treat it well. Well, I like to know that the lab can make another one if they make it by crimping it and sort of working it. The chance of getting that exact and the subsequent time is kind of unlikely. The protein buildup on the PMMA lenses, the older ones, is a certain number of years. It takes a long time for the protein buildup and it's not very toxic and the way it bothers people most is that when they clean it, they have something slightly gritty on their fingers that will cut a little canyon in the film of protein and they feel both sides of the canyon and when they have more and more of those, they feel worse and once you clean one of those, they say, wow, this is so nice. You get all the protein off, the lab will do it, but actually in cleaning lens, especially the rigid gas permeable, there are a lot of techs within the Moran system that do this so the patients can come in and they have to have that done at least once a year and some patients have to have it every six months. So either the lab or one of our wonderful techs, something like that. This is what you need to order. We'll get into this also a little later, but when ordering a rigid gas permeable lens, you've got to know what the power will be and I often work mine out of my trial set. I build up the trial set over the years, but if you're going to be involved in rigid gas permeable and fitting care to comas, call the lab and get in touch with somebody there and say, okay, how about a trial set? Mine's a 10 and mine's well with 20, 30, 40 lens or something like that. They can fix you up and you can match the base curve and the diameter and hope you'll be near the power. If you base curve the diameter about the same, you put it on the high, then all you have to do is do an over refraction and add that algebraically to the power of the trial lens you used and you know what power to order. You need a base curve and I'm going to show you the diopter slash radius of curvature table. That's the wonderful thing. You get the radius of curvature from the a keratometer or a corneal topography that you need to put down the power. You need to put down the base curve you want and the diameter and the chart on that's one. There wasn't one that was very good when I started out. I used something but I've adapted it and I have a darn good one and it's in the notes. So it'll be easy to find what diameter you want. The little color thing it's nice because if they're working over a towel or over the sink and they drop a lens, it's nice if they can see it and they have very light colors. It doesn't really change the color of the eye much but it might enhance it a little. They come in blue and brown and gray and green and the hazel kind of likes green and the blue blue and the brown brown and the gray and the grays are nice but actually I fit that one time the gray was the main color they had and I fit a lot of people that way and on the Ritchie Gasper Mibble I like the Boston lens. By the way I'm telling you what I like that doesn't represent what the university likes or what Moran likes I have no financial interest in any of these things but Boston I like the Boston lens the one called the EES and the only time I use other Boston lenses is if they come in with a different Boston lens and they're wearing them and I can refract through them and see what they have and see if they need a power change. I'll say with the one they've been in that's fine when you get your lenses if you've ordered to pair this place on the eyes and check how the fit is see if they're too loose or too too tight we'll talk a little bit about that and they need some instructions on how to use the solutions and they're not all that complex this one Boston solutions the one you put in your case the same one you rinse the lens with clean with your fingers and I two solutions I hate are saliva and water it's spitting on your lenses I just I can't tolerate that people do it and a lot of people get away with it well you can get away with something for a long time then get nailed so saliva is no choice and water you're running the chance of acanthamoeba and all you need to scratch under your cornea and give it to acanthamoeba a chance you may have something a lot tougher than what you want and they need some instruction and most of the texts at least around here are good at that and if they aren't you begin to learn how to tell them how to put them in and take them out I used to do that myself a lot it's not all that tough and people who are wearing rigid gas permeable lenses can learn how I've one of my doctor friends said you know there's a consensus that women are better with these because they have delicate little fingers and so on he said I think the men who work on the carburetors and who they who do the exciting detailed mechanical stuff are equally capable told you about the spare pair for the backup and a spherical trial lens of rgp contacts is a great thing to have and I have one it's in a box that used to contain that kind of box contains 35 millimeter slides but it also you can slide the lens case in there have separate little book they'll tell what's in every one of those stations I love that okay fitting a cone you need a cone trial set and there must be several kinds of cone trial sets and when I got one Dr. Joe it wasn't Dr. Joe's over Mr. Joe Soper an optician in Texas he developed a cone trial set and it's really nice that there are others there's one call I think them a gill and some others and find a trial set and that's not all that tough and all like that's my trial sets 10 lenses this is a Soper pterodactyl is diagnostic set and all you have to do is order the Soper number you order this lens if I want a Soper 6 because I've put it on the eye and that works well well that's a minus 1250 I refract through it it sits low it doesn't have an air bubble I algebraically add the over refraction to the minus 1250 in order and they'll do it take care of all the rest of it the sagittal depth is the depth between the back of the contact lens and the table it's sitting on that this that distance right there and if you have a little bit of sagittal depth you're not likely to be sitting right on the cone and squashing it you know when I'm fitting off the trial set I pick one that I think's right and if I'm seeing what the steepest curve is I'll take a look and if I think well maybe something like this 52 might do it they all have a 45 further more peripheral corneal curve but for the central corneal curve it's this 48 52 56 60 that one you can see they repeat and if you put it on there's an air bubble take it out and put the next flatter one on if that still has an air bubble the next flatter one it takes a little time and once you get one there's no air bubble it looks like it stays there and doesn't want her too much then you're right there order that and you you're in business the finishing of the lens edge is an ARP it's not a technical detail it's not something you set a machine on it soon it's the one that you set that wonderful lab tech in your contact lens manufacturing system to do the bevel because when you when they cut it goes right to a sharp edge so they've got to cut off that sharp edge of it around the periphery and that leaves other sharp edges you have to keep blending when you find you blend it so they're on any sharp edges and that's good I will take patients who have a brand new lens they see well with it it sits there it looks good they say doctor this doesn't feel good I've had contact for it doesn't feel good it's probably the edge problem and so I send it back I say check the edge blender the edge is too sharp and if it sounds like a dumb question I don't care if it sounds like a dumb question guess what comes back very often a better lens the one the patient likes and it so there are subtle things like that and if they think they have good quality control it's hard maybe to know how good that edge is you sort of trust that technician and also if they send another one back and they say oh I still bought it oh no it's not good I just say make another their trial and the free trial lenses and the companies will work with you pretty good on that at least the one we have now that I deal with the brand does okay soft contact lenses I already mentioned protein buildup is slower or half I haven't mentioned it's six months to a year on a rigid gas permeable is two to four weeks on a soft contact but protein buildup seems to be toxic here so non-infectious keratitis is a possibility we see this here I see it when I'm lucky I'm at the VA at a time when one comes in I just love to see him take a look it is so hard to get a history out of these people these people if you say how long do you hold your lenses before you throw them away they'll say oh four weeks I say do you keep your lenses for a while maybe maybe four months before you throw them away then they say oh no I always throw away by three months well it's a two week lens so and I phrase the question of do you ever sleep in if I say do you ever sleep with your lenses and they all say no if I say do you ever sleep with them day and night day and night on and on for three months they say oh heck I I don't think I've gone over six weeks doing that well one night's terrible time seven is bad business well seven times the six weeks so and we put out a white paper for LDS missionaries and some of them pay attention some don't those that don't get into the non-infectious keratitis it's so hard to diagnose non-infectious keratitis in Hong Kong on the telephone but I have mighty high strong suspicions and the most important thing on that is to stop wearing the lens a lot of patients are given a an antibiotic that needed that doesn't necessarily do any good but the antibiotic if it makes you feel good it's okay with me the thing that really works in non-infectious keratitis is steroids and they got so well they know they're better in a day or two days and so teaching to throw the way that the lens is the way it's recommended we talked about the treatment the best way to work with them after they've had non-infectious keratitis and absolutely insist that they never wear on the two-week lens I'm soft on that I'll let it work in four weeks but the two-week lens well if they say that they never wear it before in four weeks and they say they never sleep in them give me daily lenses so they wear lenses one day throw it away that night and just make them promise on a stack of rifles they will always throw it away that night that'll help you you can tell the movement by looking at the patient on the slit lamp and seeing kind of looking at the conjunctival vessels and the edge of the lens and get some idea there's some colored soft contact lenses we won't get into that that's more about there's some crazy ones people like to wear it Halloween so once you want to get in that a little bit okay with caution we talked about solutions this is really a nice idea find find a friend or a lab consultant and if you can deal with the big company they say you just call this number and we'll take care of you all our people are capable I tell them I'm just one person I want to talk to oh it's the same could we do that there's any possibility they'll usually help you and I do have such a friend it's been very very helpful very bright person it's not a lot of them optometrists not an ophthalmologist that sees a lot of lenses come and go and they know which ones are failing and they'll send you a free if you're going in detroit contact lenses it's really nice or multifocal bifocal contact lenses they'll send something to you and they'll kind of guess what you might want that's very very helpful also when you have a lens with the sphere in the cylinder in it you do a refraction of the sphere and cylinder on top of that which is the kind you do not just sphere the sphere and cylinder you add those two together professor worson white put all of that in one of these for me I don't know anybody else in the world had that kind of thing that is wonderful for me to add them together it was about the time that the companies were getting better it's all in their computer now they can do it for you you don't have to worry about doing that but they do have to add it and that friend will take care of that I'm saying you new trial lenses in the new power and it's so often it's great with one try okay let's talk about oh multifocal rigid contact lenses they're hardly ever done anymore my wife is wearing these so at one time and she also had toric lenses in rigid lenses I'd find her sometimes on the couch kind of watching television like this those track lenses are weighted so that they hang down and they have a worry at your cylinder she was looking at it like this I said well dear house of picture I'm pretty good I don't know how on earth would that be good because she's rotated her axis 90 degrees but I love her just the same okay this is climber once again I ran I said her University of Utah Joe hatch don't care what you use I will tell you something you can start with change the anything you'd like no problem and I told you I like the material of Boston ES now you order a base curve that is right on the flattest K reading if the central colonial curve is two diopters you'll ask just order the flattest one that's number one above two diopter cylinder order a base curve halfway between the 2k reading so if you have a 42 diopter and 45 halfway between is 4350s everybody agree order 4350 for your base curve and of course you convert it into millimeters when you when you order it and I'll show you the chart that does that and above four diopter cylinder order a base curve steeper by two-thirds the difference between the 2k readings if you have a 38 and a 44 two-thirds the distance toward the steeper 42 you agree with that okay by the way I had to develop this on my own but I did but it's right it's good I didn't ever see that written anywhere and then you use the chart to convert diopters to millimeters radius curvature order the spherical power that you want I told you about the lens now if I haven't told you about lens no matter I'll show you a chart we have it I'll show you the chart on that but that's four bullets on there one more is color that light little color so you can tell the difference from the lens of water drop and the last thing is dot the right lens with the white dot that way they always put the right lens and right eye if the lenses are almost identical I say always put the right lens and right eye anyway because someday we may change you so that it won't be that identical so get good habits to start with okay this chart is wonderful this is part of Tyler's quarterly it's a little magazine that comes out every three months it has about everything about every contact lens in it if someone comes in you're not too sure what it is but they do know the name and details of the lens you can see things about it and it might help you in your future border I don't get into this very often I don't get into encyclopedia Britannica very much either Google or whatever but when I get in I'd like to find something but this chart begins with the 20 diopter base curve goes up to 60 on the front of the cornea and for every one of those base curves and this starts here and this is a little steeper this little steeper little steeper little steeper little steeper this gets down to the steepest but if you've got a 40 diopter in front of the cornea which is quite flat let's try something 45 that's kind of mid-range you'd order a 7.50 I only go to two points past a decimal point but that that's a wonderful chart that's in Tyler's quarterly okay the flattest charitometer for the lens diameter you're only interested in the flattest k this just determines how wide the lens how big a lens so well let's go back if you have your flattest charitometer reading 45.50 over 9.3 these are a little bigger lenses and I used to fit my patients like the bigger ones I found out as I widened them about two tenths of a millimeter I'll even fudge it up another tenth I wouldn't go the other way toward the smaller ones check the lens fit if the lens is rocking and they're popping out all the time fit it steeper and go on back on this chart go a half diopter steeper so what if you have a lens it's a 46 and I say it's coming out all the time well the 46 go to a half diopter steeper 46 we go to a 46.50 7.25 instead of a 7.3 the larger the number the flatter the curve 7.3 is a larger number than 7.25 so the smaller the number the shorter that radius of curvature also if it's loose you can order a larger diameter lens the cornea isn't just one curve the cornea has a slope then a curve and then the slope the further out you fit toward the slope with a larger lens the type more like a cookie cutter at fifth because it's off to where the slope grad you becomes more gradual so you can go larger by two tenths of a millimeter and see if that will help out now when you do make the contact lens steeper or flatter you have to remember there is a lens in the tears between the lens and the cornea I'm not talking about that frontier film that has no power which you've been taught it has power forget that part but you are really changing that lens you find you're going you have to go steeper and you want to go a diopter steeper you made a stronger plus lens so you have to counter that if you have the if you already have the power right you're only working on the not slipping so much then take that one die for more plus lens and put minus one in the power of the contact lens and you'll still have the same power in front of the eye if they seem tight it's just the opposite cut back to a flatter contact lens a larger radius of curvature or smaller contact and we just mentioned the tear lens power there is a tear lens there it's real and we talked about soft the edges okay soft spherical contact lenses for plane just a cosmetic fitting for revision I like actually OASIS OAS YAS is the way they smell it and here are the details they're all they're all on the box they're only two base curves 8.4 is for steeper caratometer readings such as 46 diopters 47 48 up through there 8.8 is for flatter ones 45 44 so depending upon what the flat the flattest caratometer readings the flattest caratometer reading is you know if it's above 46 or below 46 and you know whether the 8.4 series of lenses the 8.8 they're all 14 millimeters diameter it's their only refraction over the free trial lens and you add that algebraically to the you add the over refraction to the lens power and that way you know what power you want there is an inside out laser mark 1 2 3 on the lens that little tiny dots of 1 2 3 if you see a backward 3 2 1 you understand backward on the eye virtually never see that somehow the patients know when they've got it when they've put one inside out they're taught how to see how it's cupped maybe try to cup it a little more like you fold a taco it's that taco fold goes toward each other then then you're right you've got the cup the way you want it if you try to fold it like a taco and it flares out better turn it over it's probably inside out okay next step if you have a stigmatism there is an acutal view oasis for stigmatism and by the way i very frequently use others because that's what my friend my lab consultant has told me so i've been into cooper lenses and other things that's where you want that person because they know which lenses are getting ordered which ones seem to be satisfied for which ones that seem to fail they have a sense of that they see it in a in a larger number of cases in one's individual practice but this lens only has one base curve it's 8.6 it only has one diameter 14.5 have someone send you a free torque torque trial lens and if you don't have that you might try the just sending in your usual refraction findings and let the lab guess for you and send you a trial lens that still works because you over refract over that and you can get right on it again be with your consultant it's very soon over refraction the one two three on the lens edge you want it to be correct the two-week lens replacement i've told you four weeks it's okay for me often the soft mold the focus aren't too bad one thing is if you have a given power if you have a tube i have to add on it sometimes it seems like it's about 1.5 or something to the way it works you you chance to over-plussing you're less than under-plussing that the adcubus oasis presbyopia or others there's a lot of good multifocal lenses out there one base curve only that's 8.4 one diameter only 14.5 how do you know those you go to a box on the trial lenses that where the optician is where you are in a clinic and read those numbers off there i put them on on the order but they would if i said i wanted action view oasis for presbyopia i got an eight four base curve and a 14.3 diameter no matter what because that's all they have and you order that power low just low mid or high you don't give them an number lowest 0.75 1.25 mid is 1.5 and 1.75 and high is two to two and a half now it's important to do to find the dominant eye on these because some of the people who make these lenses put a different ad on the dominant eye than they do on the non-dominant you all familiar with you feel comfortable about getting the dominant eye and finding it it's a simple thing have a little triangle keep both eyes open look at it there then close one and close the other as i close one the image jumps a little bit to the right no big importance as i close the left it jumps way to the right the one where the image jumps the furthest from the center is a non-dominant eye work on that little bit that works really nicely because they want to know that work with your consultant that's all great mono vision by the way the percentage of success in uh multifocal lenses is well above 50 60 70 it's this way up there you might have a few of them as but maybe a 70 or 80 and the percentage success on rigid lenses when they were weighted and had the power down in the bottom of theoretically if you look down then your lower eyelid would hold the lens and push the bifocal in place well you all know the anatomy assessment if you look down the lower eyelid goes down too so unless they split it push it up those don't work all that much they're based on a false premise motivation to read or contact with the non-dominant eye power about one and a half over what the distance prescription would be is a good way to go if you want to do that success in monovision however it's around 30 success it's not staggeringly wonderful some patients just put storiders over their contact you know all kinds of storiders you go to the drugstore and you pay 15 20 dollars 10 dollars you go to the dollar store and every pair of glasses there is one dollar well the A the residents keep saying go anywhere you want well tell them about the dollar store too that's easy for those guys i love the acu view too acu view then number two this lens fits a little bit like a rigid lens somehow it has a little body to it i say kind of like it slurps up some of these signatures maybe up to one and a half diopters so if you fit an acu view oasis on some eyes they don't like the leftover cylinder and you put the acu view too on they might like it and it's fine so it's a it's a nice lens do the spherical over refraction which you had then again i think most of the opticians have trial sets of acu view two lenses so you can try one out if you like many low power tour guys do not see with it it has only one base curve a bigger part has to 8.3 for the steeper k's 8.7 for the flatter these numbers a little different from what you see on other lenses but those are the two again based on 48 is the midline less than 48 or more than 48 guide you toward what you want they're all 14 millimeter diameter and they have the laser mark daily disposable soft contacts i like the one day acu view true i there's another one called the one day acu view moist the acu view true i cost a little more it's probably a little better material in the making good patient acceptance when you order those they get enough lenses that they put one in every morning and throw it away every night one base curve 8.5 one diameter 14.2 and if you want guests i like them replaced every day without fail now if you need a one-day lens for a stigmatism repressed opi then you are into the acu view moist they don't the true i doesn't have that ladies and gentlemen i feel with what you've heard today with this paper that i worked over spend a lot of time actually you can see the dates is november 2016 i've worked it and reworked it with that especially the fourth page on which is the intimate details of how you go about it i think you can have success in fitting contacts it can be a lot of fun it's a lot of fun for me now you might think it's kind of tough you might think oh i don't know if i can do it well you can do it even if it seems kind of chancey you reckless bunch skiing and the slash and all that stuff are there any questions i'd like this paper to get out to everyone all the residents who are not here can somebody help with that another i don't know how many there are there were 14 of those do you need more than that or does that cover it if you need any more tell me but if you'd be sure and get them distributed because it's it's reading on there i love contacts they're fun i've kept a lot of people out of the operating room i love corneal transplants this is time one if you failed with contacts and those care to colonize a lot of those people get along with glasses for a while in contact for a while when they fail with that they just can't see and they can't make it then we do a corneal transplant i've kept a lot of people out of the operating room with a good contact lens fit with an rgp lens rigid gas permeable thank you very much


Hello everyone, I am Swati Gargay, Assistant Professor, Department of Civil Engineering from WIT, Solapur. Topic for today's session, Water Treatment System. Learning outcome of this session, at the end of this session, learner will be able to explain water treatment process. This is a simple line diagram of water treatment process. First, water is collected from the natural source of water, say river, or some reservoir is constructed near the river, through that water is collected, then that raw water is stored in a water treatment plant, then after treatment that water is stored in an elevated service reservoir, elevated service reservoir is nothing but the water tank, then after sufficient storage of water, water is distributed in a distribution network. So, we will see in detail what are the units in water treatment plant, how it is treated there. So, these are the units of water treatment plant, first the water is collected from the river intake, then it is sent to the water treatment plant by constructing some jack well, then after treatment water is stored in a elevated service reservoir and then it is distributed. So, we will see in detail what are the units of water treatment plant, so that in the box all the units of water treatment plant are there. The first unit is a screen chamber, in the screen chamber all the floating insoluble materials, say water bottle, plastic bag or any other large material removed from the water. So, this is the pre-treatment and after that water sent for the aeration. In the aeration water and oxygen comes in close contact, so that water is purified, then after purification some coagulant agent will be added in a water. Alum is the best example of coagulant agent, due to that all the tiny dust particle in water sample stick together and it is forming a flow in the water, flow is nothing but the large or heavy dust particle forming in the water sample. So, after flocculation that heavy dust particle should be settled down at the bottom, so that it is sent in the sedimentation tank. In the sedimentation tank flow settled down at the bottom, so that water sent here slowly, so that it gets sufficient time to settle down at the bottom and it settled down due to gravity and after settlement it removed from the bottom of the tank. Then water is sent for the filtration, filtration it is the layer of sand and gravel through that water filters and that filtered water go for the chlorination, chlorination is nothing but the disinfection, so the chlorine is added in a water to remove some pathogenic bacteria or to prevent water bond diseases. Then that clear water store in a elevated service reservoir, after sufficient storage water is distributed in a distribution network, so this is the line diagram or this is the flow chart of water treatment plant. This is the alternate flow chart of water treatment plant, so that it is more clear what is flocculation, what is sedimentation to you. See here there is a raw water, after screening and after aeration coagulant agent will be added in the water and after addition of coagulant agent some flow formation will be start, so that black dots showing the flow formation and all the small dust particles stick together and forming a large and heavy particles. This process is called as the flocculation and then it has to settle down at the bottom, so for that it is sent in the sedimentation tank, so in the sedimentation tank all the heavy particles are settling down at the bottom of the tank. Then clear water is sent for the filtration, see filtration it is the layer of sand and gravel, so through that water filters and here we get the filter water and after some doges of chlorine it is stored in the tank and after sufficient storage water is distributed, so it is showing that it is supply to the house. So we have seen the flow chart and we have seen the some alternate flow chart also, now we will see the theoretical definition of that unit, so first unit is screening chamber, so first unit is screen chamber, so screening chamber it is a first unit operation of water treatment plant that separate large floating material from the water. Second unit is aeration, it is a physical process which bring water and oxygen in close contact in order to remove dissolved gases, dissolved gases say CO2, H2S, CH4, etc. Then third flocculation, it is the process in which tiny particle of dirt in water stick together to form flocs in water, so that formation of flocs is called as the flocculation, sedimentation it is the physical water treatment process which removes suspended solid from water with the help of gravity. These are the some images of units of water treatment plant, this is the intake tower installed in a river, so raw water is collected from the source of water showing in the image, after that it is sent to the water treatment plant, so first unit in a water treatment plant is a screen chamber, so there is a screen which remove large floating material or some insoluble material, this is a picture of mechanical aeration, machine is rotating the water, so that all the surrounding air getting mixed in the water and it get oxygen and it get purifies, this is a image of cascade aeration, water is flowing from the steps, water is flowing over the steps, so that it get sufficient time to mix oxygen in a water, this is a multi tray aeration, from one tray to another tray water is passing and while passing the air getting mixed in the water, there are many types of aeration but few of them I have covered in this session, now you pause video here and answer the question which is the correct flow of water treatment plant, in the option there are four flow chart, you select the correct flow chart of water treatment plant, first option is the correct option, firstly the water enter in a screen chamber, then it goes for the aeration, after aeration is go in the sedimentation tank and after sedimentation filtration is there and after filtration we get a clear water, so this is the correct flow of water treatment plant, after aeration some coagulant agent say alum is added in the water and it form and it cause the flow formation in the water that flow has to settle down at the bottom, so that water is sent in the sedimentation tank with the slow rate of flow, so that due to gravity all the heavy particle will settle down at the bottom showing in the image and this is the picture of sedimentation tank, this is a image of circular sedimentation tank, after sedimentation water is sent for the filtration, see here the dirty water is there and after filtration we will get the clear water, then after filtration some chlorine dosage will be given to water and then that clear drinkable water stored in a water tank and after sufficient storage it is supplied to house to house, these are my references for this video, thank you very much for watching.


Okay, so I'll speak with, yeah, it's great to be here. Thank you very much. So, yeah, I'm going to talk to you a little bit later, and we have a community, a community, and I think it is pretty cool. And of course, that's going to have honouring to be done at the same time, right? Yeah, so I've been working, yeah, for a year now, but, you know, it is a really fantastic effort, and if, you know, 100% of that with Instagrams, yeah, we're trying to bring a lot of standardizations to the way that basically people, you know, really find Instagrams, or they break them, a lot of people, that's another thing to touch. So, you see, like this at the hour of the day, a lot of incredible format, and you can see here that, you know, hopefully it should be very easy to define very standardized functions, people should be able to share the same configuration, in a popular pattern. But, you know, the first thing I mean to do is be able to actually share the metrics. So, anyway, that's a little bit about making metrics. You know, I want to talk a little bit about, like, where M3 is next up with, I'm Australian, so I usually go there, down to the end, you know, the one that's the most in M3. So I hope these bring you up. And we also have, like, one of the main things that will happen, like, one of the most, right, so, is, like, actually, metrics, where I think that, like, the challenges in operating at the hour, in the beginning to see, people look at that and they can make a spread like that. So, you know, this term can come around pretty often. I want to, especially to give you an example of, you know, in high-parameter use cases, I think, in high-parameter use cases, really, very quickly. So to make a single metric, like, they should be satisfied. And you basically try to coordinate that. So basically, you want to contract the occurrence of different steps, those, over time. So, when you think about the dimensionality space in this metric, there's a few different dimensions that, you know, we would like to, tomorrow, I'm going to say, perhaps, route the status code, optimize the version. And then when you multiply these dimensions together, that's the resulting V&A time series that we need to track. So if we look at some numbers here, you know, you can roll these metrics up to make viewing the code fast. And here, you can see that there's a few metrics on the left here that have, like, a region tag, a priority tag, and, of course, a status. And there's a lot of each of these across as the route tag as well. So you're welcome to have this really stringing off the region tag, stringing off the client tag, and then starting the results of those all together. So, you know, that makes, at least, like, when you want to view these really high-parameter metrics, you know, in a, you know, across regions or across lap versions, quick. However, just to store the raw data still, you're going to be highly dimensional. And then, the example we have here is basically a 500-nation P-Route, my status code, by regions that, you know, backends already and, say, 20 client versions. And that's 250,000 V&A time series. It's expensive, a little too bad. If you have a whole bunch of client versions or, you know, have any other connections on it, it destroys millions pretty quickly. And, you know, you've kind of got people maybe you just don't need some of these tags. And that's fair, but there's definitely, I think, going to be some tags. However, to go into, like, a concrete example of, like, at least by some of these are important, if we're monitoring a, you know, a back-end that runs out of two regions, and I realize I'm debating what these regions need to go over. So, that's fine. So, say, you're not in the U.S. and, you know, if you're basically got the status quo metric, well, you're not monitoring my SQL Redis you just get, or if the protection is another subsystem, you're not monitoring. Mike is not working. So, basically, you've got two regions you've eaten off the U.S. and you're monitoring the status quo at the edge. And say that, you know, you're monitoring the status quo, so you're not really monitoring all the subsystems that use applications. So then, if Redis nails, say, in a single region, and you can see here that we've basically got these two clients that don't necessarily talk to the same resources. So, for a client, we want, like, three. It's only talking to my SQL to the client, and then hitting the application here in comparison data. However, the client, B2, is going to a different platform here by my SQL Redis. So, you know, it's a fancy chat feature that I'm using Redis on. So, if Redis nails, and, you know, something that you're not specifically tracking, you want to up this from, you know, the very edge of your network of, like, where are the errors happening? If you don't have the region tag, then you won't know basically where to start looking. And if you don't have the vibration, you won't know that, perhaps, you know, you should not be tracing the code path for the B2 point, not the B1.3 or the B1.3 pressure itself. So, this is why, you know, these tags can be really, really important. And, you know, so Prometheus really is an absolutely fantastic system that I think everyone should get started on Prometheus. It's no reason to jump into a more complex and hardcore lowering system. So, you know, you're really starting to hit the layer of, like, any multiple Prometheus instances. But when you do start to hit that, I think, you know, it's basically about choices like, how do you make Prometheus's or look to the blockchain storage? And this is, you know, the design of Prometheus and the blockchain storage is basically there to solve this problem. So, we have a simple high-fab electric, you know, and you can try to solve that again. It actually starts to look different because if you've got some that are very full, you might topple them over in the end. Basically, there's a new one and you're utilizing it for very high. Or, you know, you have to basically stick up entirely in the new one. So, can you mention to I'm already wrote today, like, basically the background of why it was even important for us to work in this space. So, we have a lot of metrics. I learned things, you know, very little in the 86 school. We first learned how to use the first tag, and they won't be starting to tag metrics. And, you know, we now have about 100 million pre-aggregated metrics per second. And that translates into, I think, 30 gigabytes per second of network traffic for many of our applications here. And then, you know, after that we basically down sample those metrics into 10-second tiles and 1-minute tiles that store basically a value for each one of those restrictions. So, as well as some 10-minute tiles and 1-hour tiles, which are stored for months and years. But most of the real-time data in the month data is stored in 10 seconds or in the last few days, then 1-minute for the last 30 to 60 days. So, I meant that, you know, network traffic is 30 million metrics per second. So, I mean that when you're doing metrics in our index. And then, you know, in Congress we basically have a portion of that 20 to 50 percent of the traffic to power dashboards and 150,000 of those every month. And now I want to look at, like, what why might be interesting to look at how a place with 3D foreground. So, you know, as I mentioned, the radius is an absolutely fantastic solution that you should definitely start using if you're just beginning time monitoring. And then, pretty much, you know, if you never really exceed a single meter, it's a very good way to really basically set up a module of so much GSD. But what to do, more if you want something that is most unified with the extension of the radius systems. Then, you know, we have a speed open source, we share the solution a lot to add to more of the people like, as we use the country back because we would love to have to, you know, re-evaluate it again the next time we go to work with another company. And, you know, it's basically pretty nice, easy to get started. We'll try to get both scout out but also scout in in terms of how you run it. We use a bunch of microphones, but we could write a lot of these in embedded mode. So, when you can see again that actually in itself, you know, it's a time series database in very index. It even embeds the extension key binary in the same binary when you run the values cluster. And it's actually very dedicated across as well. And it's actually used for cluster membership routing, metric rule propagation, stuff like that. So, basically, you know, the high level architecture, I wanted to be a little bit deeper today. So, it's kind of like an L7 obstructive registry design kind of with, you know, for cost efficiency, and actions, very, very low. Basically, no data every time so if we know that we're going to have to kill it, potentially in this mode as well. But we really try to make sure that the disk is not constantly writing itself so you're not being spent with the actions and memory is kind of looned in the other stage of the actions. And we also do all that in front as a series in the actual case.  You know, so I wanted to get a little bit into basically how we look at these time series on disk. So, you know, when a query comes in, once we resolve the action area, we basically, for any one of these time we go straight back, you can see minus 3, minus 4 hours, minus 1, minus 5, 6, all the way back, across one sort of a basically when we're on a single node and we're going through a time limit, what, say between two and four can, we basically first check a window filter which can match the capacity of the server if we need to look up. We basically search the disk for the given time limit for a given metric.  So, you know, we can give the window filter to give about one the same false positive range.  You basically, the API is you can give it a y-ray or basically a string and say, I want to add this to the set and then when you can figure basically m and n and n, you can basically input numbers though that n can input numbers for your m and k. And k is the number of hashes, basically the hash that string in place ones in appropriate places across the mid-set. And then basically you call back that window filter and say, this string doesn't exist there. And I'm going to cover in that, in much more detail but it's a probabilistic set that goes into action as such. And we can figure out that this is basically give about one percent false positive of the naturally. So now I'm going to talk about how can we actually find that metric on the inner side of the window block. So for a two before the end of the window we basically do that window filter and if it says yes you can find that there for the two before the end of the block. Then we go to the summary file and we do a library search by the nearest index history. So if you can imagine that if you're looking for the metric cap and the current value is dark we're going to do a library search to start. We're going to go to that in this kind of lesson then that the current value is bottom. So now that's before the current tree and cap and then we're going to basically say that was the voice that we found now it's literally scanning and it is done so that the pages as they're being born and buried from the end up that we should try which he says about one or two pages for any country that we're looking at. So if in this example you go to and now with that cap knowing how the tax data offset we need to look at their file we're going to go to that data and check something before we check what we're going to find. Let's talk a little bit about the entry and entry index. The entry index is one of the same uses FST segments which we don't know what exactly it uses until the initial press state sector for the past index. So this is a search engine that's going to make a value so every time we find a label thing that we can pull up the roaring in that basically decode it by attaching the containers to get that memory and then be able to intersect a lot of these various file results together. So you can see in this example like if I was entering into this series it's a little bit like a trial a compromise trial so you can hear in this example we'll put the word R and C and they both essentially match the same value free so we compress the trial and the facts together and free in this case we basically put to a roaring bit about that action is much better than any sense. So for every term combination in form of say servicing this food we basically make store of this and that's the question and if you have a query that says servicing to N.5 N.5 version 3 you know we are basically to resolve that query we need to intersect we have servicing to N.5 N.5 version 3 and you can imagine where if you have a project CSA like N.5 then we threatening to span and match all the what the actual lane values are matched by as well and that's what N.5 does so once we found more concrete based than lane values in due access then we need to intersect the roaring bit paths associated with all of them together we calculate 1% or 3 of them and then as you guys are working with these classes as well so that you can just drop the beautiful indexes when they're there in the middle where actually basically pull back we have to pour the result during the time we go and that's great because in the meeting setting you have pieces of like elastic storage and similar you basically have a whole bunch of release to basically to get the name that's outside of your TPL where you have to do like expectations and stuff which is kind of sad to the point where we don't care about the database itself so you know essentially they're just a more efficient in-map so the roaring bit maps represent the 2 in the end space and the rest of the columns are over except 242 which is the 64 for every to 16 space they use a different container depending on the cardability basically in that range of integers that it's trying to represent so you know for a really dense bit map it'll probably choose it for a really dense key mesh in 2016 it'll probably use bit map it'll use a kilobytes memory of course once that it'll probably start with a rank it'll sort it out to do that and then the run-off encoder is trained for all contiguous points of types that actually exist like D.C. and here I'm outside so I can literally have a mesh in there inside the one on the other it's the run-off so you know I'm not actually going to jump in this but basically in the way of what I'm going to do it's kind of powerful but also kind of easy to use actually you basically allow your own competes with a convenience operator there are two roles to run entry again and entry for one there so you're not running like a compact so you're not running query nodes next to everything and you're not running a whole bunch of other roles because there's more that you can do for example but of course you can put them separately if you're not in my solution what do you use for graphite today? if you're using graphite you might have something that looks like this as I looked like this last week you can actually use graphite as a free now and basically sort of all you can do is hang graphite makes it free which is pretty cool because a lot of people still have pretty old and that's what sells for the metrics so you can use graphite when I was breaking and I was going to talk about the research but we don't have enough time to do that do you want me to run it better? yes great if anyone would like to hold my microphone that would be really so I'm going to explain personally this is the channel and we're talking about the area it's all and just if you want to look at it later first of all that you have is the anti-venom anti-venomator anti-permefius anti-romine this is basically what's the gist here you can see here that we've configured for graphite to some in a sum policy for two seconds and the only thing that doesn't match that is aggregated by me aggregation policy and for permefius we're going to just store everything in the eye between the graphs so when we started this place we were running through the screening we were going to base it on the purpose what's happening we're going to create a topology placement so you can see here we're going to use the topology proposed in 3D C in 3D B we're going to use these four shards because this is a cd shard then we're going to create an aggregated namespace which is for most of the media space we're going to create the aggregated namespace and so on we're going to use this graphite and now we're going to put the file which is now also running on this and then we're going to use


Okay, so great job on the exam. It was very hard, I get that. Chris suggested to me it might be a little bit hard, but I wouldn't with it anyways, so I want to blame Chris for everything, but I'll take the heat on that. So you guys did great on a hard exam. We're continuing on on lecture 9, Addition to Sigma Star, and really there's two reactions that we're thinking about when we talk about addition to Sigma Star orbitals. One is proton transfers, where you attack a proton. The other is SN2 reactions where we attack carbon, and in each case the leaving group leaves simultaneously. It's a concerted displacement reaction. And we've spent the first part of lecture 9 talking about proton transfers. We're almost done, and I want to finish up our discussion of proton transfers by talking about equilibria. Whenever you draw out some long drawn out mechanism for an esterification reaction or an immune hydrolysis, anything, you tend to have lots of proton transfers in those reactions, and I want to encourage you every single time there's a proton transfer step in your mechanism to try to estimate the equilibrium constant for that reaction. And I'm going to give you one example. There's nothing special about this reaction. It's acid-catalyzed removal of a THP protecting group. If you were to draw out the mechanism for this reaction, really all of the business here is occurring at this pyrann, and I'll draw out just one of the many proton transfer steps in this mechanism. This PY stands for pyridinium. That's PPTS is pyridinium peritoluene sulfonate. It's really just toluene sulfonic acid mixed with pyridine so that pyridinium is the real acid in this reaction. And so let's draw out this reaction where pyridinium is acting as an acid and somehow reacting with this tetrahydro pyranol. This is a THP protecting group. And let's think about what's the first step in this process. And how much interesting thing, how much interesting, how interesting can we get with this step? So if I draw out the arrow pushing for this step, I'll end up with a transfer of a proton to give an oxonium ion that's oxygen with three bonds and a positive charge on there. We can say a lot about this. How likely is that? Is that a good mechanism? Why didn't I protonate this oxygen? Is that occurring under the conditions of the reaction? So let's go ahead and try to estimate the equilibrium constant for this step and every step where there's some kind of a proton transfer. And what power do we have? The power that we have is pKa's. We don't know. There aren't tables full of rate constants there. You just can't find that kind of information out there. But what we have at our disposal are lots and lots of tables of pKa's. It's very easy to do a titration in water. And so let's use that information. The pKa for a pyridinium ion, we talked about the pKa for an aminium ion before where you have a protein on an sp2 hybridized nitrogen atom. That's about 100,000 times more acidic than an ammonium ion for something like triethylamine. And the pKa for this is about 5. That's for any sp2 hybridized nitrogen with a proton on it. If we come over here to this protonated oxonium ion, that's kind of like a protonated ether, protonated alcohol. The pKa for this particular example is pretty close to the pKa for a protonated ether. So I'm going to use a pKa for minus 4. So this is not exactly a regular ether, but close enough for our purposes. As long as I know the pKa's of the two acids on each side of this equation, I can accurately estimate the equilibrium constant of this reaction. I told you that proton transfer reactions are fast. Probably under the conditions of the reaction, no matter what this does, this is probably an equilibrium because proton transfers are much faster than the reactions that break carbon-oxygen bonds, carbon-carbon bonds and things like that. So let's assume that this is an equilibrium and our picture for this reaction is that we're generating some amount of this and then this sits around and slowly does some dissociation step. Okay, so what's this super secret equation that we're going to use here? Our super secret equation, and I'm going to draw it in another pen color, is this. Keq for this step is equal to 10 to the, and it's going to look kind of sloppy and confusing here, but I'm going to write pKa for product minus pKa for reactant. Now I'm pretty bad with math, but even I can handle this equation, right? So let's go through and do the math here. So the equilibrium constant for the forward-looking process here is like this. Keq is equal to 10 to the products minus 4 minus the pK for the reactants, which is 5, which is plus 5, which is equal to 10 to the minus 9. I immediately have some deep insight into what's going on in this reaction. When you mix peridinium, peritoline sulfonate with some sort of an ether, what you can expect is that one out of a billion molecules is protonated. By choosing to use PPTS, you've set up conditions where the ratio of deprotonated to protonated is 1 to 10 to the 9, you know, that's enough zero. So the ratio of these two species, and again, it's ratios that are intuitive to you when you do reaction mechanisms. For every billion molecules, only one of them at any point in time is protonated. And it's this that's sitting around waiting to slowly dissociate that. If you want this reaction to be faster, use a stronger acid. You'll have a higher fraction of these molecules protonated at any point in time. Yes? You need to know some. I'll give you some later that you have to memorize. I'll just give you a set and I'll say memorize these. So we're getting, that'll be in a later lecture. Okay. So, okay, what's the caveat? There's lots and lots of PKA's that have been measured out there because it's so easy to do a titration. They're almost all aqueous PKA's. So there are going to be some differences when you take into account, well, this is not exactly water, methanol is not exactly water, and especially in organic solvents. Feel free to use your aqueous PKA's anyways. It's better than nothing. It'll still give you insight. And unless I, I can't imagine asking you some question where it'll make a difference that you did it in an organic solvent. I'd rather you use an aqueous PKA than not to try to think in these terms. I'd rather you thought with, with these kinds of numerical terms using aqueous PKA's. How does it change? Depends. In this case I'm going from neutral to charged but you can imagine other cases where you go from negatively charged to neutral and that's what has an impact. In other words are you going from neutral things to charged things or charged things to neutral things? That's what affects these things. Okay. So let me step back. We're done with proton transfers. I said in this lecture we're going to talk about two different types of addition to sigma star. In the case of proton transfers we're talking about addition to sigma star for some sort of hetero-atom proton bond. And so I would draw it like this and I could take exactly the same nucleophile, exactly the same arrow pushing and attack a carbon atom and now it's not the same orbital anymore. Now I give it a different name.  Okay. So how are these different? What I mentioned to you before is it is fundamentally different to displace, to do a displacement reaction on proton because that's a first row atom. So remember our periodic table, H is over here in one corner of the periodic table in the first row. And then over here in the second row we've got carbon. So carbon is more massive. A methyl group is more massive than a proton by a factor of 15. If it's 15 times more massive it vibrates more slowly back and forth, you can look in an IR and confirm that. So immediately you should suspect that additions to carbon are going to be, that kind of displacement at carbon is going to be slower, significantly slower. But there's a difference here in what's driving these reactions. In proton transfers remember the actual mechanism involves formation of a hydrogen bond. So even though both of these types of reactions are governed by this fundamental equation that we talked about on day one, it turns out that proton transfers are mainly governed by charge. This is mainly a charge interaction. That's why proton transfers are so fast. There's very little of this filled MO, unfilled MO business powering this and making it fast. It's the fact that bases tend to have negative charge. Protons have a lot of positive charge and things that are acidic. Now why are SN2 reactions going to be fast? It turns out that it's not the charge that's making this, it's contributing for the reason why hydroxide can attack here. But I could take neutral thioethers and they'll still attack fast here. In most SN2 reactions, this is the dominant species. It's controlling that. So the arrow pushing looks very similar but different features for proton transfers versus SN2. Okay, so let's talk more about SN2 reactions. And those are the things that will form carbon-carbon bonds. So we have to be interested in SN2. But as you can tell from discussion section and maybe just generally talking with me, I hate SN2. I hate it. Because after one year of sophomore organic chemistry, it's the first reaction you learn. You learn it throughout the entire year. You use it throughout the entire year and you overuse it. You use it in every single case where you shouldn't ought to be using that. And so I'm going to do everything I can to dissuade you from overusing SN2 reactions. Okay, I want to start off by looking at the transition state for an SN2 reaction just in a very generic sense here. So if I draw the three things attached to the carbon that's undergoing displacement, so I'm trying to draw this edge on very three-dimensionally. And so you can imagine me displacing something like bromide over there or iodide. And in that transition state for an SN2 reaction, we have the nucleophile coming in and simultaneously displacing the leaving group. As this bond is getting shorter or as this distance is getting shorter, this distance is getting longer. Now in that transition state, if you look at the distribution of charges, it looks something like this, the important point is the carbon is starting to pick up positive charge in the transition state. As this carbon, as this X group is leaving with those electrons, even as the nucleophiles coming in, you start to build up positive charge. There is a transfer of charge from these R groups to this partially positive charge carbon in the transition state. And we'll see the impact of that in a second. So I'll just write this down. Negative charge, if these R groups are doing their job, negative charge is being transferred from the alkyl groups on the periphery. We would call these equatorial. We would call these up and down ligands on a trigonal bipyramidal structure. We would call those axial. Okay, let's, the implication of this idealized transition state is that electroneg, and this is true of any trigonal bipyramidal structure. It can be an organometallic species. It can be silicon. It can be phosphorus. Or it can be carbon. And it can be a transition state. Anything that is trigonal bipyramidal, electronegative substituents, prefer to be equatorial. Whoa, what did I say? That doesn't sound right. Axial. I'm immediately starting to freak out here. Prefer to be axial. Alkoxy groups, they prefer to be axial. Of course, that makes sense. Alkoxy tends to be something like a nucleophile. Electropositive groups, I don't have an abbreviation for this while I'll write out electropositive. So if you want to have fast SN2 reactions, of course, you want to have electronegative leading groups. Chloride, bromide, iodide, acetate, oxonium ions. You want to have electronegative nucleophiles, hydroxide, thiolate. And if you really want it to be fast, you want to have R groups attached to that center that's being substituted, excuse me while I tie my shoe. You want to have R groups attached to that carbon atom that's being substituted to be electropositive in nature. Let's see the impact of that on substitution rates. So if you look at the rates of SN2 substitution on various chloromethanes, what would you find is you increase the number of chlorines attached to that carbon that's undergoing substitution if I compare these. These all have just one carbon atom. And so what would I see if I compared the rates of these SN2 substitution reactions? What you'd find is that the fewer carbon substituents or the fewer chlorine substituents you have on there, the faster it is. This is faster than two chlorines. Dichloromethane is slower to do SN2 reactions on. That's convenient because you often use it as a solvent. When you do some SN2 reactions, I wouldn't but it's at least slower than chloromethane and that's not supposed to be arrow. I apologize for that. It's supposed to be greater than. We're talking about rates. Yeah. So and this is faster to substitute than chloroform. Chloroform is a better solvent for SN2 than, well, I mean it's also a little bit acidic on that proton but in general it's slower to do SN2 reactions on chloroform. That would be very rare for you to see somebody doing an SN2 reaction on chloroform. And carbon tetrachloride, very slow to substitute. And it all has to do with this preference for you not to have electronegative substituents attached to the carbon. And you might argue, oh, that's a steric effect. You don't know what you're talking about. That's just sterics. So let's take a look at a different example. I'll just take a look at propyl, well, butyl chloride. That's what I have numbers for versus this ethoxy. Now here, it's hard to argue that sterically, that this is more sterically encumbered. Oxygen has less sterics on it than the CH2 over there. And yet this one is five times slower. It's five times slower than a comparable SN2 reaction of just plain butyl chloride. That's not sterics. This is the effect of the fact that you've got this oxygen. And the oxygen has this polar effect. You could call it an inductive effect on that carbon that's undergoing substitution. There's no conjugation going on here. The oxygen is not directly attached to the carbon that's involved. But it's an important effect to keep in mind. Now it's a factor of five. Maybe that's not very big, but it's still an effect. Okay, so let me keep talking about this trigonal bipyramidal structure. Because this feature of trigonal bipyramidal structures is not just SN2 transitions, it's intermediates, anything with that trigonal bipyramidal structure. Let's take a look at something else that has trigonal bipyramidal structure. So let's take a look at some sort of a molecule like ammonia. And of course, this is not interesting with protons on there, but imagine having three different alkyl groups. And now this is a chiral center. If I have three different alkyl groups on here. But you'll have a hard time isolating one and antimirror versus the other because it's very, very fast for a means to invert. And if I draw out what the transition state for that inversion looks like, it looks trigonal bipyramidal like this. And in that transition state where everything is planar, as it flips up like an umbrella, in this transition state, you're going to have the electrons in this p orbital. If the H's are planar, there must be a leftover p orbital here. I'm not going to phase the orbital. And then finally, this thing inverts so that the lone pair is now at the bottom. So very, very fast for a means, this process. And if instead of H you have alkyl groups, you, those are not, those centers are not considered stereogenic because this inversion is so fast. Okay, what happens if I replace nitrogen with other atoms? And I'll give you the inversion barriers for these as I replace nitrogen with other atoms in the periodic table. So what am I giving you? I'm giving you inversion barriers. And you can compare this by substituting nitrogen and ammonia for these other types of ligands. So what happens if instead of nitrogen, I have a carbanion? Let's just create ourselves a mini periodic table here. So if I have a carbanion with a lone pair here, how fast do carbanions invert like ammonia? If you look at, and I'm giving you some calculated numbers, so what's important is kind of not the exact number here but the sort of, the relative numbers are important. So if I look at carbon minus, 13 k-cal per mole inversion barrier is actually very fast. That means it's fast at room temperature. And indeed, if you try to make chiral carbanions where that's a C minus there, you will have a very hard time trying to work with and isolate those before they invert. Good luck. Put nitrogen there. It's a little slower but still fast at room temperature. Just slower than carbon, I guess is all I can say. And finally, if it's an alkoxide, well, that's not too meaningful because there's two lone pairs but at least we have a number for that and it's 1.7. Okay, so the important point here is not the differences between all of these. What's important is we drop to the row below this and go to third row atoms. Watch what happens to the barriers. That's supposed to be oxygen plus, by the way. Phosphorus, and I don't know why I'm putting 0.7. If you wrote 35 and 38, you get the big picture here. I'm regretting having done that. Okay, there's a huge jump going from second row atoms to third row atoms. This inversion type process that we saw for ammonia, silicon, anions, they just don't invert. If you somehow had a way to make a silicon anion with three substituents on there, you should expect that to retain its stereochemistry. Even at elevated temperature, you'd have to heat that very hot to get a silicon anion to invert like this and lose stereochemistry and to racemize. Phosphines, you can buy chiral phosphines where the phosphorus atom is the chiral center. They don't do this. This kind of an inversion barrier means you have to heat it to get it to invert and you'd have to heat it very hot. Sulfur plus, again, that's not really that relevant as something you'd have to worry about inverting, but you can see that everything in this third row is now slow to invert. So it's a general principle. The carb anions are fast to invert. Well, these numbers came from calculations. They calculated the energy of the transition state and subtracted the energy of the grad state. K-cals per mole, sorry. Yeah, everything, every number I give you in this, I should have written that down, but every number I give you is K-cals per mole. So there are cases where you will have seen that people have made and worked with configurationally stable alkyl lithiums. For all intents and purposes, for the purposes of inversion, you can think about the transition states for inversion of this, alkyl lithium is being similar to the carb anion. Your prediction should be that if you put electronegative substituents on here, on this carbon atom, it should invert more slowly. If you put electronegative substituents on that carbon atom, it should be harder to gain access to that trigonal bipyramidal transition state. That's why whenever you see people work with configurationally stable, and let me make this configurationally interesting by having three different groups on there, there always will be some sort of a heteroatom attached to the carbon, an electronegative heteroatom. That's when you can start to slow down this inversion process. Let me draw the back end of that orbital down there at the bottom. That's when you start to slow down this inversion enough to where you can actually work with those kinds of carb anions before they racemize at that center. It's when you have an electronegative heteroatom. So in this particular case, the transition state energy for inversion of carb anions like this is about 23 kcals per mole. And that's right at the point where if you keep it cool, minus 78, you can work with those configurationally stable. Oxygen substituted alkyl lithiums before they invert. Okay, so those are all properties of trigonal bipyramidal transition states. Okay, so let's drop down to that third row, silicon and phosphorus, and let's talk about the substitution. So oftentimes you'll see stuff like this. We're going to see a lot more of this later on in the course, maybe Mukayama-Aldol reactions where you have o-silo groups, protection of molecules with TBS chloride, when you're going to want to substitute that silicon off of there. Whenever you draw substitution reactions at silicon, they are never SN2. It's never SN2. It's slow to achieve these trigonal bipyramidal transition states.  So the transition state to get closer to that is just not good. It's better to have an intermediate. So if I draw out the correct mechanism for substitution of that silicon to pop off the carbonyl, what I want to do is do this and then stop drawing. Don't pop off the leaving group as we're attacking. This silicon, I mean it's not great, but it's perfectly happy here with these five things attached with silicon, and maybe that's going to bother you a lot. And you won't want to do it, even though I'm telling you, don't do SN2, you're going to have a tendency to want to pop that leaving group out, don't pop it out. You can have six bonds to silicon. There's no octet rule for silicon, that's the second row. You can make stable structures, silicon 8s. You'd have six bonds on silicon. There's nothing wrong with these five bonds here. Now, after you do this, now you can break that silicon oxygen bond to make the carbonyl leave. So again, even though I'm telling you this and it sounds like a simple rule, I'm going to catch you every time you try to do SN2 at silicon and say, hey, we said don't do SN2 concerted reactions at silicon. Okay, so the important point is it's the intermediate that really is trigonal bipyramidal. It's not the transition state. In the transition state, you're getting closer and closer to trigonal bipyramidal. Okay, so let's, anytime you see some sort of pentavalent silicon, let me just say something about the language I'm using. Let me pull this back down for a second. You might have heard me refer to this as a silicon 8. I had that ending 8 on there. Every time you hear me add 8, pallidate, cuprate, silicon 8, hydridoborate, that 8 tells you there's a negative charge on that atom. And whenever there's a negative charge on that atom, every single bond becomes nucleophilic. So I'm usually really particular about this kind of language because it's informing you of something. It's telling you something about the reactivity. So listen for that. When you hear me refer to something as a cuprate, pallidate, boronate, hydridoborate. Okay, because these intermediates in substitution processes resemble trigonal bipyramidal transition states, all those same rules apply. If I were to show you this silicon 8, this is the preferred geometry for this. So notice in this intermediate, I've got acetoxy displacing from the back side in a two-step mechanism. Notice how careful I was to draw a trigonal bipyramidal intermediate there in the silicon substitution. When you look at stable silicon molecules or intermediates in processes, the electronegative substituents want to be axial in that intermediate. The electropositive groups like R groups or H want to be equatorial. So in general, when you substituted silicon, nucleophile tends to attack opposite from the side of the electronegative leaving group. So when you substitute with TMS chloride and you've got some chloride leaving group, the alkoxy group is going to come in from the opposite side of the electronegative leaving group, that's the preferred geometry.  It's not impossible, but it costs you. It's not as favorable as coming in from exactly the opposite of this bond that you're breaking. That's favored coming from the backside. So just to put some numbers on that, if I compare the energies of this versus this, where I have one of the fluorine's equatorial now and not both of the maxial, this structure is 8.3 k-cals per mole higher in energy to have an electronegative leaving group on the side. How many times more stable is it when the electronegative groups are axial? So we can convert k-cals per mole into factors of 10, meaning you can, I'm not smart enough to divide that by 1.4. A millionish, I'll take that. So it's a millionish times more stable. What that means is if you draw some sort of reaction where this things comes in from the side rather than opposite to the leaving group, it's like a millionish times slower as a penalty. Now, of course, this can't reach around. That has an entropic advantage, but you should worry if you've got your alkoxy group attacking silo chloride from the side, because that's a million times slower than if it could have attacked from opposite to the leaving group. Okay, so let's translate this into biology. This is essentially a model for DNA. It can be alkoxy groups there. So if I had this sort of a, this sort of, this would be a phosphonate ester, and I displace this or hydrolyze this with alkoxide. And many, many enzymes do phosphoryl transfer. Polymerases, ligases, anything that transfers DNA, kinases, phosphatases, they all involve some sort of oxygen atom attacking a phosphate ester. I want to start off by drawing the resonance structure for this so that we can decide what's the preferred trajectory of attack. Hydroxide can add from four different types of directions here in order to displace that alkoxy group. But according to our rule, what's the most electronegative group that's attached to this phosphorus atom? I've got two methyls, those are equal. I've got O minus, and then I've got neutral oxygen. What's the most electronegative group attached to this? No, not O minus. Because O minus is negative. It's got plenty of electron density. The neutral O. It's kind of convenient. That's what we're going to displace. And if you look at the idealized transition state for this, the ideal transition state would be to have, I'll draw it as a solid arrow, will be to have the hydroxide attack anti to the ethoxy group. That's the preferred trajectory of attack. It's not to attack opposite the P double bond O. It's to attack opposite the leaving group. And this goes through an intermediate that we call a phosphorane.  It's not concerted. And if you wanted, you could have drawn out this P double bond O resonance structure the whole way through. Every single enzyme that has ever been studied, kinases, ligases, phosphatases, polymerases, every single one obeys this rule of stereoelectronics. No enzyme has ever been found in which the nucleophile does not attack anti to the bond that's leaving. The bond that's, the group that's leaving always has some sort of a hydrogen bond to, I won't draw it to poison the structure, but it always has some hydrogen bond to it that further increases the electronegativity of that group. So nature understands this simple rule and applies it every single time it designs an enzyme. Okay, so now I'm going to go back to something that I hope will be well known to you and very obvious, but it's not so obvious that I can skip it. I'm going to give you a set of four numbers here for, these are approximate relative rates for nucleophilic displacement of alkyl halides. I'll start off with alkyl, with ethyl halide. I'll compare that to this, which now has a second, an extra methyl group on there. I'll put a third methyl group on there. And then finally, I'm going to make a, draw out another primary alkyl halide here. And I'll give you the relative rates for SN2 reactions. So this should just be clear. We're talking about SN2 rates. This is the fastest one of the bunch, the primary alkyl halide. I hope you already knew that primary alkyl halides are faster for SN2 than substituted alkyl halides. This has one extra methyl group at what we refer to as the alpha position. So we refer to this as the alpha position relative to X, and we refer to that as the beta position. The more things you add to the alpha position, the slower it gets to do SN2. It becomes more slow. I'll qualify that in just a moment. And so it's six times slower when we add that one methyl group on there. And if we compare this to T-butyl, now it's on the order of 100 times slower than these other two. It's very slow to do SN2 substitutions at tertiary centers like this. But finally, when we get to this system, which is still primary, right? The first one is primary. This is primary. This has beta branching. The methyl groups are at the beta position. And unfortunately, there is no way that a nucleophile can come in and attack from the backside without bumping into one of those methyl groups. There is no possibility for that to avoid the bumping. And so now we're looking at an SN2 rate that's about 100 times slower than T-butyl. So we call this a neopental center. This is called neopentane or a neopental halide. So neopental are the slowest SN2 reactions based on sterics. So that kind of substitution pattern where you have beta branching, three beta substituents next to a leaving group. Those are the worst of all possible SN2 reactions. Don't propose stuff like that. Don't design syntheses based on those.  Not as much as this. Well, I mean, there's still an orbital that's back here. It's, you know, if I came in from the side here, then maybe it would be worse. But we're coming in from the back end. My line drawing doesn't do it justice. Maybe that's why it's good for us to memorize the numbers. Yeah. If you have an electronegative substituent beta on any of these, it'll be slower. It'll be even more slow. But you're asking in terms of relative numbers. I'd have to go back and look at that alkoxy ethyl group. It was like a factor of five slower. So imagine if I put an alkoxy group here, maybe five times slower than that. I'm just estimated. Yeah. Wait, say that again? If I fuse this to something to have like a chain like this so that it was leaving, is this? It looks to me, I'd have to look at that. I would expect that to still be slow, still be a problem. But would it still, would it be this much slower? Maybe not. In other words, there could be ways you could torque it away to make a little extra room. So I wouldn't know the numbers for that. Okay. So let's talk about three-membered rings. Because this will turn this on its head. It's like you think you know everything once you know these rules I do. I'd be like, oh, I got sterics, slower, tertiary sucks, never substitute tertiary centers. Of course we know that. I hope everybody knows that.  Whoops. And here's what I want to draw. So I want you to contrast these two species. Just a simple epoxide where we're opening with alkoxides.  You get preferred addition to the primary center. But if you do that kind of ring opening under acidic conditions, there's no alkoxide roaming around when you've got sulfuric acid in there. That's not what makes the reaction fast. If you do reactions with catalytic acid, it's the neutral alcohol that's attacking. And it's not the epoxide that's opening up, it's the oxonium ion, the protonated epoxide. And in these cases, preferred attack happens at the tertiary center every time. And this is a general principle. If you have some kind of rule in mind that attack at tertiary centers is always slow, that's wrong. Here's the exception. And it's general. So it doesn't matter whether you're looking at aziridinium ions, oxonium ions. It doesn't matter whether that's a H or whatever. Mercurinium ions, we don't teach oxymercuration reactions anymore, but we used to. It's, your prediction ought to be whether it's metal, oxonium, aziridinium, that the nucleophile always attacks at the more substituted center. Focke-roxidation, if you know that reaction, it's all the same. More substituted centers get attacked more quickly. The fallacy is that if you draw it where these bonds are equal in size, then it's not so obvious what's going on. This bond's already partially broken. It's already a longer bond in the intermediate. I just didn't draw it that way. So if you want to make it easier to understand, you could draw these kinds of things like this where you have a tertiary center. And here's this prebroken bond with this leaving group just ready to leave. I mean, maybe that'll help you understand why it's faster to add to the tertiary center. But this, you have to be very careful with these three-membered ring-onium ions. As far as I know, that's not true for four-membered rings, five-membered rings, six, just three-membered rings where this is true. So let me give you another series of compounds and we'll look at the relative rates for SN2 reactions. So here's another butyl chloride. In this case, it's a Finkelstein reaction where you exchange chloride for iodide. So you use these by sodium iodide and acetone. And these are always SN2. Well, for most typical substrates that you would use. So let me go ahead and change the structure of this alkyl chloride here and we'll look at the rates for this SN2 substitution process. And your tendency may be to want to take your SN1 thinking and apply it to this. And just remember, this is SN2 we're talking about here. So I'm going to assign this a relative rate of 1 and we'll compare these other substrates in terms of how fast iodide displaces chloride. If you look at this alkyl chloride here, sterically it's pretty similar to the butyl. I just didn't have the number for propyl. So sorry about that. Propyl and butyl will be pretty similar. It's 33 times faster. So in other words, when you have pi systems nearby, allyl, benzyl, not only are they faster for SN1, they are also faster for SN2. It's faster for everything. Substitute's faster than that. What's surprising and maybe not so obvious is when we go to this, that would definitely be slower for SN1, having an electronegative cyanogroup there. You don't want to make a cation next to this electron acceptor. But if you're doing SN2 reactions, that's a benefit. 3,000 times faster for SN2. If you have to do SN2 reactions, make sure there's a pi system next door. 35,000 times faster. I wish my research could go 35,000 times faster. And I'm telling you how to do that if you're doing SN2 reactions. Okay, I want you to contrast the transition states for SN2 and SN1 reactions. And let's start off by thinking about SN1. We've already had a lot of practice with that. And so I want you to think about this process where you simply ionize that. And what's happening in the transition state for this? I want to try to draw a transition state and I'm going to break these down into some really fundamental orbitals here. So in my transition state, I'm going to try to make this almost pyramidal, not yet. It's a very late transition state. This X is starting to get farther and farther away. It's not quite planar yet. It's trying to get planar. And here's this pi system next door, this double bond. So here, I'll try to draw that sort of bending backwards a little bit. And I'm going to try to sketch out some orbitals here. In the transition state, this is starting to look almost like a P orbital. It's not quite pure P, but the late transition state for an SN1 reaction, it almost looks like a carbocation. And meanwhile, this X group is leaving and it's kind of overlapping with its orbital with this empty P orbital as it's leaving and marching away. So the transition state in terms of if I were to decompose it into these orbitals, it would look something like this. So the bottom line is that with an SN1 reaction, with that empty P orbital there, and this is a general property of SN1 transition states, there's kind of not enough electrons. That's a sad, sad carbon atom that has an empty P orbital. Not enough electrons as we get closer and closer to this carbocation intermediate in the transition state. And so maybe you can tell why it might be happier. If right next door, we had a filled, I'm trying to make sure I phase this correctly. So here's that pi double bond. Look how great it is that we've got this filled orbital right next door to help donate electron density into that sad, sad, carbocation type species that's starting to develop. So that's why SN1 is faster when you have that little bond next door. Now I want to contrast this situation. I hope I have enough room here. With a carbonyl next door. And not an SN1, I want you to think about an SN2 reaction where a nucleophile is displacing the leaving group, pushing it out like this. And let's draw out that transition state. Now the transition state is total, not just close to planar, but is exactly planar. Pretty close to exactly. Depends on which of these is whatever. It's close to planar. Okay, so let me go ahead and draw this out in that transition state. It's different now. I've still got this sort of p orbital shape here. If it's planar, if this carbon is planar, there has to be a p orbital or an MO, a molecular orbital in the transition state that looks like a p orbital. I've got this leaving group leaving with its pair of electrons, that's a filled orbital. I've got this nucleophile with its pair of electrons, that's a filled orbital. We've got all these orbitals that are filled now. Leaving group, nucleophile. The problem here is too many electrons. There's too many electrons in this transition state. With the nucleophile coming in with all its electrons, there were already enough electrons in here to have covalent bonds and now you're coming in with your extra electrons, that's the problem. And so now we have a very different solution. Now having not just a pi bond here, but a carbonyl here is a better acceptor. Now we have pi star orbitals here that are very low in energy and good at donating and let me phase this and I'll phase this so we can see that as we start to build up too much electron density and we start to fill this orbital, it gives us somewhere to go. We've got somewhere to donate the extra electron density. So SN1 reactions, not enough electrons. SN2, we're looking for a donor to really help us. And that's why carbonyl is better than a simple C-C pi bond. Say again, yeah this, sorry I didn't label this, this is pi star now because the extra electrons, as the electrons fill this orbital, now that can donate into this anti-bonding orbital for CO. So you're giving the electrons somewhere to go. Okay, I'm going to have to stop there. We're almost done with SN2, thank God. And we'll pick up with that when we come back on Monday.