Q.11-50b - Organic Chemistry (Mcmurry)

Question

Question: What products would you expect from the reaction of 1-bromopropane with each of the following? 

(b) KOC(CH₃)

Step-by-Step Solution

Answer

Answer

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{Br+KOC(CH}}_3{\text{)}}_2\text{→H}\mathrm{OC}{({\mathrm{CH}}_3\text{)}}_2{\text{+CH}}_3{\text{CH}}_2{\text{CH}}_2\mathrm{OC}{({\mathrm{CH}}_3\text{)}}_2\text{+KBr} \\ \text{ Elimination reaction } \\ {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2\text{Br+}\mathrm{KOC}{({\mathrm{CH}}_3\text{)}}_2{\text{→CH}}_3{\text{CH=CH}}_2\text{+KBr} \\ \text{ Substitution reaction } \end{gathered}$$

Step1: S N 2 reaction

It is a nucleophilic substitution reaction in which old bond is broken and a new bond is formed. Both the processed occur simultaneously. Hence, it is a single step reaction.

Two reacting species are involved in the rate determining steps. 

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2\text{Br+}\mathrm{KOC}{({\mathrm{CH}}_3\text{)}}_2{\text{→CH}}_3{\text{CH=CH}}_2\text{+KBr} \\ \text{ Substitution reaction } \end{gathered}$$

Step2: E 2 reaction

It is a nucleophilic elimination reaction in which old bond is broken and a new bond is formed. Both the processes occur simultaneously and no intermediate is formed.

Here, carbon hydrogen or halogen bond break to form new double bond. Hence, it’s a single step reaction.

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{Br+KOC(CH}}_3{\text{)}}_2\text{→H}\mathrm{OC}{({\mathrm{CH}}_3\text{)}}_2{\text{+CH}}_3{\text{CH}}_2{\text{CH}}_2\mathrm{OC}{({\mathrm{CH}}_3\text{)}}_2\text{+KBr} \\ \text{ Elimination reaction } \end{gathered}$$