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Organic Chemistry: Intro to Organic 4

Rate Law Problems

The Rate Law

Leaving Groups and Nucleophiles

Problem :

C2H5O- + CH3Br→C2H5OCH3 + Br-    

The above reaction has the following rate law:

rate = k[C2H5O-]a[CH3Br]b    

If [C2H5O-] is tripled while [CH3Br] is constant, the rate of the reaction also triples. If [CH3Br] is doubled while [C2H5O-] is constant, the rate of the reaction is also doubled. What are the values of a and b? What is the overall reaction order?

There is a one to one ratio of proportionality for both reactants. The values of a and b are both one. The overall reaction order is the sum of a and b, two.

Problem : Which one of the following steps is rate-limiting?

The conversion of B to C has the lowest rate ( 10-5 ). This is the rate-limiting step.

Problem : Sketch the reaction coordinate vs. energy for the reaction given in the previous problem.