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

Question

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

(e) ${\text{Na}}^{+ {-}^{}}\text{C≡CH}$

Step-by-Step Solution

Answer

Answer

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{{\text{Br+Na}}^{+}}^{-}{\text{C≡CH→CH}}_3{\text{CH}}_2{\text{CH}}_2\text{C≡CH+NaBr} \\ \text{Substitution reaction} \end{gathered}$$

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 is a single-step reaction.

Two reacting species are involved in the rate-determining steps

Step2: Reaction of CH 3 CH 2 CH 2 Br+Na + - C≡CH

It is a substitution reaction in which C-Br is broken and the C-C ≣H bond is formed in a single step process, which means the bromide ion is substituted by -C ≣H ion. Hence, it is a substitution reaction, and bromide and -C ≣H ion are nucleophiles’ so-called nucleophilic substitution reactions. 

$$\begin{gathered} {\text{CH}}_3{\text{CH}}_2{\text{CH}}_2{{\text{Br+Na}}^{+}}^{-}{\text{C≡CH→CH}}_3{\text{CH}}_2{\text{CH}}_2\text{C≡CH+NaBr} \\ \text{Substitution reaction} \end{gathered}$$