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

Question

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

(a)  NaNH₂

Step-by-Step Solution

Answer

Answer

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{Br+NaNH}}_2{\text{→CH}}_3{\text{CH}}_2{\text{CH=NH}}_2\text{+NaBr} \\ \text{ Elimination reaction } \\ {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{Br+NaNH}}_2{\text{→CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{NH}}_2\text{+NaBr} \\ \text{ Substitution reaction } \end{gathered}$$

Step1: S N 2 reaction

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

Two reacting species are involved in the rate-determining steps. 

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{Br+NaNH}}_2{\text{→CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{NH}}_2\text{+NaBr} \\ \text{ Substitution reaction } \end{gathered}$$

Step2: E 2 reaction

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

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

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{\text{Br+NaNH}}_2{\text{→CH}}_3{\text{CH}}_2{\text{CH=NH}}_2\text{+NaBr} \\ \text{ Elimination reaction } \end{gathered}$$