44bE - Organic Chemistry (Mcmurry)

Question

What effect would you expect the following changes to have on the rate of the reaction of ethanol with 2-iodo-2-methyl butane?

(b) The concentration of the ethanol is halved by adding diethyl ether as an inert solvent.

Step-by-Step Solution

Answer

S N 2 reaction

It is a nucleophilic substitution reaction in which an old bond is broken, and new bond is formed. Both processes co-occur. Hence, it’s a single-step reaction.

The two reacting species are involved in the rate determining steps.

Rate of the reaction

In  $S_{N}2$ rate of the reaction depend on the reacting species and nucleophile.

Hence, on half the concentration of ethanol, the rate of the reaction decreases as well as on adding dimethyl ether as a solvent decreases the polarity. Thus, the rate decrease and the response become slow.

$\begin{array}{c}R\text{\hspace{0.33em}}=K\left(R.S\right)\left(N\right)\\ =K\left(\frac{1}{2}\right)\\ =\frac{K}{2}\end{array}$