Ethanol Ethanol
Systematic name Ethanol
Other names Ethyl alcohol,
grain alcohol,
drinking alcohol,
Molecular formula C2H5OH or C2H6O.
Molar mass 46.06844(232) g/mol
Appearance colorless clear liquid
CAS number [64-17-5]
Density and phase 0.789 g/cm³, liquid
Solubility in water Fully miscible
Melting point −114.3 °C (158.8 K)
Boiling point 78.4 °C (351.6 K)
Acidity (pKa) 15.9 (H+ from OH group)
Viscosity 1.200 mPa·s (cP) at 20.0 °C
Dipole moment 5.64 fC·fm (1.69 D) (gas)
MSDS External MSDS
EU classification Flammable (F)
NFPA 704

NFPA 704.svg

R-phrases R11
S-phrases S2, S7, S16
Flammable limits
in air (by volume)
3.28% - 18.95%
RTECS number KQ6300000
Supplementary data page
Structure & properties n, εr, etc.
Thermodynamic data Phase behavior
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Related compounds
Related alcohols Methanol, 1-Propanol
Other heteroatoms Ethylamine, Ethyl chloride,
Ethyl bromide, Ethanethiol
Substituted ethanols Ethylene glycol, Ethanolamine,
Other compounds Acetaldehyde, Acetic acid
Except where noted otherwise, data are given for

Ethanol, also known as ethyl alcohol, drinking alcohol, or grain alcohol, is a flammable, colorless, slightly toxic chemical compound with a distinctive perfume-like odor. It is best known as the alcohol found in alcoholic beverages. In common usage, it is often referred to simply as alcohol. Its molecular formula is variously represented as EtOH, CH3CH2OH, C2H5OH or C2H6O.


Physical properties

Ethanol's hydroxyl group is able to participate in hydrogen bonding. At the molecular level, liquid ethanol consists of hydrogen-bonded pairs of ethanol molecules; this phenomenon renders ethanol more viscous and less volatile than less polar organic compounds of similar molecular weight. In the vapor phase, there is little hydrogen bonding; ethanol vapor consists of individual ethanol molecules. Ethanol, like most short-chain alcohols, is flammable, colorless, has a strong odor, and is volatile.

Ethanol has a refractive index of 1.3614. Ethanol is a versatile solvent. It is miscible with water and with most organic liquids, including nonpolar liquids such as aliphatic hydrocarbons. Organic solids of low molecular weight are usually soluble in ethanol. Among ionic compounds, many monovalent salts are at least somewhat soluble in ethanol, with salts of large, polarizable ions being more soluble than salts of smaller ions. Most salts of polyvalent ions are practically insoluble in ethanol.

Furthermore, ethanol is used as a solvent in dissolving medicines, food flavorings and colorings that do not dissolve easily in water. Once the non-polar material is dissolved in the ethanol, water can be added to prepare a solution that is mostly water. The ethanol molecule has a hydrophilic -OH group that helps it dissolve polar molecules and ionic substances. The short, hydrophobic hydrocarbon chain CH3CH2- can attract non-polar molecules. Thus, ethanol can dissolve both polar and non-polar substances.

Several unusual phenomena are associated with mixtures of ethanol and water. Ethanol-water mixtures have less volume than their individual components: a mixture of equal volumes ethanol and water has only 95.6 percent of the volume of equal parts ethanol and water, unmixed. The addition of even a small amount of ethanol to water sharply reduces the surface tension of water. This property partially explains the tears of wine phenomenon: when wine is swirled inside a glass, ethanol evaporates quickly from the thin film of wine on the wall of the glass. As its ethanol content decreases, its surface tension increases, and the thin film beads up and runs down the glass in channels rather than as a smooth sheet.



The chemistry of ethanol is largely that of its hydroxyl group.

Acid-base chemistry

Ethanol's hydroxyl proton is weakly acidic, having a pKa of only 15.9, compared to water's 15.7[1] (Ka of ethanol is a measure of <math>\scriptstyle \frac {[C_2H_5O^-][H^+]} {[C_2H_5OH]}</math>. Note that Ka of water is derived by dividing water's dissociation constant, <math>\scriptstyle[H^+][OH^-] = 1.0 \times 10^{-14}</math> moles2/liter, by its molar density of 55.5 moles/liter). Ethanol can be quantitatively converted to its conjugate base, the ethoxide ion (CH3CH2O), by reaction with an alkali metal such as sodium. This reaction evolves hydrogen gas:

2CH3CH2OH + 2Na → 2CH3CH2ONa + H2
Nucleophilic substitution


CH3CH2OH + HBr → CH3CH2Br + H2O









CH3CH2OH → H2C=CH2 + H2O




Ethanol combusting in the confines of an evaporating dish

Combustion of ethanol forms carbon dioxide and water:

C2H5OH + 3 O2 → 2 CO2 + 3 H2O


94% denatured ethanol sold in a bottle for household use


Ethylene hydration


C2H4 + H2O → CH3CH2OH






C6H12O6 → 2 CH3CH2OH + 2 CO2












Near infrared spectrum of liquid ethanol.

The product of either ethylene hydration or brewing is an ethanol-water mixture. For most industrial and fuel uses, the ethanol must be purified. Fractional distillation can concentrate ethanol to 95.6 percent by weight (89.5 mole percent). The mixture of 95.6 percent ethanol and 4.4 percent water (percentage by weight) is an azeotrope with a boiling point of 78.2 °C, and cannot be further purified by distillation. Therefore, 95 percent ethanol in water is a fairly common solvent.




At pressures less than atmospheric pressure, the composition of the ethanol-water azeotrope shifts to more ethanol-rich mixtures, and at pressures less than 70 torr (9.333 kPa) , there is no azeotrope, and it is possible to distill absolute ethanol from an ethanol-water mixture. While vacuum distillation of ethanol is not presently economical, pressure-swing distillation is a topic of current research. In this technique, a reduced-pressure distillation first yields an ethanol-water mixture of more than 95.6 percent ethanol. Then, fractional distillation of this mixture at atmospheric pressure distills off the 95.6 percent azeotrope, leaving anhydrous ethanol at the bottoms.

Prospective technologies






Types of ethanol

Denatured alcohol



Completely denatured alcohols are formulations that can be purchased for any legal purpose, without permit, bond, or other regulatory compliance. It is intended that it be difficult to isolate a product fit for human consumption from completely denatured alcohol. For example, the completely denatured alcohol formulation used in the United Kingdom contains (by volume) 89.66 percent ethanol, 9.46 percent methanol, 0.50 percent pyridine, 0.38 percent naphtha, and is dyed purple with methyl violet.[13]

Absolute ethanol


It is not possible to obtain absolute alcohol by simple fractional distillation, because a mixture containing around 95.6 percent alcohol and 4.4 percent water becomes a constant boiling mixture (an azeotropic mixture). In one common industrial method to obtain absolute alcohol, a small quantity of benzene is added to rectified spirit and the mixture is then distilled. Absolute alcohol is obtained in the third fraction that distills over at 78.2 °C (351.3 K).



Currently, the most popular method of purification past 95.6 percent purity is desiccation using adsorbents such as starch or zeolites, which adsorb water preferentially. Azeotropic distillation and extractive distillation techniques also exist.

Pure ethanol is classed as 200 proof in the United States, equivalent to 175 degrees proof in the (now rarely used) UK system.

Neutralized ethanol



As a fuel


The largest single use of ethanol is as a motor fuel and fuel additive. The largest national fuel ethanol industries exist in Brazil (gasoline sold in Brazil contains at least 20 percent ethanol and hydrous ethanol is also used as fuel).[14] In order for ethanol to be suitable for use as a replacement to petrol in its pure form, it must be distilled to at least 70-80 percent purity by volume before use. For use as an additive to petrol, almost all water must be removed, otherwise it will separate from the mixture and settle to the bottom of the fuel tank, causing the fuel pump to draw water into the engine, which will cause the engine to stall.[15]

Today almost 50 percent of Brazilian cars are able to use 100 percent ethanol as fuel, that includes ethanol only engines and flex fuel engines. Flex fuel engines are able to work with all ethanol, all gasoline or any mixture of both, giving the buyer a choice for a perfect balance between price/performance issue. That was only possible due to the capability of an efficient sugar cane production. Sugar cane not only has a greater concentration of sucrose (about 30 percent more than corn) but is also much easier to extract. The bagasse generated by the process is not wasted and it is utilized in power plants becoming a surprisingly efficient source of electricity. World production of ethanol in 2006 was 51 billion liters, (13.5 billion gallons), with 69 percent of the world supply coming from Brazil and the United States.[16]

One method of production is through fermentation of sugar. Ethanol creates very little pollution when burned. Millions more acres of land are needed if ethanol is to be used to replace gasoline. Pure ethanol has a lower energy content than gasoline (about 30 percent less energy per unit volume). At gas stations, ethanol is contained in a mix of ethanol and gasoline, otherwise known as gasohol. In the United States, the color yellow (symbolizing the color of corn) has become associated with the fuel and is commonly used on fuel pumps and labels.



As reported in "The Energy Balance of Corn Ethanol: an Update,"[19] the energy returned on energy invested (EROEI) for ethanol made from corn in the United States is 1.34 (it yields 34 percent more energy than it takes to produce it). Input energy includes natural gas based fertilizers, farm equipment, transformation from corn or other materials, and transportation.

Oil has historically had a much higher EROEI, especially on land in areas with pressure support, but also under the sea, which only offshore drilling rigs can get to. Apart from this, the amount of ethanol needed to run the United States, for example, is greater than its own farmland could produce, even if fields used for food were converted into cornfields. For these reasons, many people do not view ethanol alone as a solution to replacing conventional oil. Others, however, disagree, pointing out that ethanol production does not necessarily have to come from the farming of corn. For instance, Liquid Fuels of Ohio produces ethanol from expired groceries.

Politics has played a significant role in this issue. Advocates for wheat, corn and sugar growers have succeeded in their attempts to lobby for regulatory intervention encouraging adoption of ethanol,[20] stimulating debate over who the major beneficiaries of increased use of ethanol would be. Some researchers have warned[21] that ethanol produced from agricultural feedstocks will cause a global food shortage, contributing to starvation in the Third World.

This has led to the development of alternative production methods that use feedstocks such as municipal waste or recycled products, rice hulls, sugarcane bagasse, small diameter trees, wood chips, and switchgrass. [22] These methods have not yet reached the stage of commercialization.

Research shows that fuel consumption increases with the concentration of ethanol in a fuel blend. An Australian study concluded that a 10 percent ethanol blend (E10) yielded a 2.6-2.8 percent increase in consumption.

Blends of up to 10 percent are normally regarded as the safe maximum for a vehicle designed to operate on petroleum. However ethanol blends can run at up to 85 percent or higher in specially designed flexible fueled vehicles.


Rocket Fuel


Alcoholic beverages






Chemicals derived from ethanol

Ethyl esters





Vinegar is a dilute solution of acetic acid prepared by the action of Acetobacter bacteria on ethanol solutions. Although traditionally prepared from alcoholic beverages including wine, apple cider, and unhopped beer, vinegar can also be made from solutions of industrial ethanol. Vinegar made from distilled ethanol is called "distilled vinegar," and is commonly used in food pickling and as a condiment.



CH3CH2OH + (CH3CH2)2NH(CH3CH2)3N + H2O


Other chemicals


Other uses



Wine with less than 16 percent ethanol is vulnerable to bacteria. Because of this, port is often fortified with ethanol to at least 18 percent ethanol by volume to halt fermentation. This helps retain sweetness, and in preparation for aging it becomes possible to prevent the invasion of bacteria into the port, and to store the port for long periods of time in wooden containers that can 'breathe', thereby permitting the port to age safely without spoiling. Because of ethanol's disinfectant property, alcoholic beverages of 18 percent ethanol or more by volume can be safely stored for a very long time.


Metabolism and toxicology



In the human body, ethanol is first oxidized to acetaldehyde, then to acetic acid. The first step is catalyzed by the enzyme alcohol dehydrogenase, and the second by acetaldehyde dehydrogenase.

Magnitude of effect


BAC (mg/dL) Symptoms[23]
50 Euphoria, talkativeness, relaxation
>140 Decreased blood flow to brain
300 Stupefaction, possible unconsciousness
400 Possible death
>550 Expiration

The amount of ethanol in the body is typically quantified by blood alcohol content (BAC), the milligrams of ethanol per 100 milliliters of blood. The table at right summarizes the symptoms of ethanol consumption. Small doses of ethanol generally produce euphoria and relaxation; people experiencing these symptoms tend to become talkative and less inhibited, and may exhibit poor judgment. At higher dosages (BAC > 100mg/dl), ethanol acts as a central nervous system depressant, producing at (progressively higher dosages) impaired sensory and motor function, slowed cognition, stupefaction, unconsciousness, and possible death.

Acetaldehyde toxicology





A) Preliminary Test


B) Lieben's Iodoform Test


C) Vitali Reaction

  • With 1 mL of sample (Ethyl Alcohol), add 3 drops of Carbon disulfide and a pellet of Potassium hydroxide in a small evaporating dish. Heat and when most of the carbon disulfide has evaporated, add 1 drop of Ammonium molybdate solution (1:10). Acidify with concentrated Sulfuric acid. Positive results gives a violet-colored solution. Acetaldehyde and Acetone react similarly and would yield the positive result.


  • Ethanol-water solutions greater than about 50 percent ethanol by volume are flammable (in some cases ethanol will burn at as low as a 45 percent solution) and easily ignited. Ethanol-water solutions below 50 percent ethanol by volume may also be flammable if the solution is vaporized by heating (as in some cooking methods that call for wine to be added to a hot pan, causing it to flash boil into a vapor, which is then ignited to "burn off" excessive alcohol).

See also


  1. Andrew Streitweiser Jr., and Clayton H. Heathcock, 1976, Introduction to Organic Chemistry. Macmillan. 215
  2. J.E. Lodgsdon, 1994, "Ethanol." In J.I. Kroschwitz (ed.), Encyclopedia of Chemical Technology, 4th ed. 9: 820. New York: John Wiley & Sons.
  3. J.E. Lodgsdon 1994, 817
  4. Ethanol Biorefinery Locations. Renewable Fuels Association. Retrieved February 2, 2009.
  5. Caroline Wyatt, 2006, Draining France's 'wine lake'. BBC news. Retrieved August 14, 2007.
  6. Steve Inskeep, 2007, Japan Plans Its Own Green Fuel. Morning Edition, NPR. Retrieved August 14, 2007.
  7. S.W. Mathewson, 1980, The Manual for the Home and Farm Production of Alcohol Fuel. Retrieved February 2, 2009. Berkeley, CA: Ten Speed Press. ISBN 0898150302 Drying the Alcohol. Retrieved February 2, 2009.
  8. S.K. Ritter, 2004, "Biomass or Bust." Chemical & Engineering News 82:22:31–34.
  9. Tom Clines, 2006, Brew Better Ethanol. Popular Science Online. Retrieved February 2, 2009.
  10. Dhinakar S. Kompala, Maximizing Ethanol Production by Engineered Pentose-Fermenting Zymononas mobilis. Department of Chemical Engineering, University of Colorado at Boulder. Retrieved February 2, 2009.
  11. Providing for a Sustainable Energy Future. Bioengineering Resources, Inc. Retrieved February 2, 2009.
  12. R. Rapier, 2006, "E3 Biofuels: Responsible Ethanol" R-Squared Energy Blog. Retrieved February 2, 2009.
  13. Great Britain, 2005, The Denatured Alcohol Regulations 2005. Statutory Instrument 2005 No. 1524. Retrieved February 2, 2009.
  14. M. Reel, 2006, "Brazil's Road to Energy Independence" The Washington Post. Retrieved February 2, 2009.
  15. Gasohol, E-85, and pure alcohol vs. "Make your own". Retrieved February 2, 2009.
  16. Renewable Fuels Association Industry Statistics. Retrieved August 14, 2007.
  17. First Commercial U.S. Cellulosic Ethanol Biorefinery Announced. Renewable Fuels Association. Retrieved February 2, 2009.
  18. Renewable Fuel Standard Program. United States Environmental Protection Agency. Retrieved February 2, 2009.
  19. Hosein Shapouri, James A. Duffield, and Michael Wang, The Energy Balance of Corn Ethanol: an Update. United States Department of Agriculture. Retrieved February 2, 2009.
  20. U.S. seeks to boost ethanol, biodiesel. USA Today. Retrieved February 2, 2009.
  21. U.N.: Not so fast with ethanol, other biofuels. MSNBC. Retrieved February 2, 2009.
  22. Air Pollution Rules Relaxed for US Ethanol Producers. Truthout. Retrieved February 2, 2009.
  23. L.A. Pohorecky and J. Brick, 1988, "Pharmacology of ethanol." Pharmacology & Therapeutics 36(3):335-427.
  24. Triglycerides, American Heart Association. Retrieved February 2, 2009.



Retrieved February 2, 2009.

External links

All links retrieved October 4, 2013.


