Q11 P. - Organic Chemistry (Mcmurry)

Question

Rank the following substances in order of their expected ${\mathbf{S}}_{\mathbf{N}}\mathbf{1}$ reactivity:

Step-by-Step Solution

Answer

Nucleophilic unimolecular substitution reaction S N 1

The ${\mathbf{S}}_{\mathbf{N}}\mathbf{1}$ reaction is a nucleophilic substitution reaction where carbon-halogen bond is broken which results in positively charged carbon, and then nucleophile attacks the carbocation and forms a new bond. Only one reacting species is involved in the rate determining step of the reaction. The term ${\mathrm{S}}_{\mathrm{N}}1$ stands for substitution nucleophilic unimolecular. The hydrolysis of tert-butyl bromide with aqueous NaOH solution is an example of ${\mathrm{S}}_{\mathrm{N}}1$ reaction.

Order of the expected S N 1 reactivity

${\mathrm{S}}_{\mathrm{N}}1$ reactivity is related to carbocation stability. Thus, substrates from the most stable carbocations are the most reactive in reactions.

Least reactive   $\to$ Most reactive

 

             vinylic                        primary                        secondary                 allylic