Question

multiple choice 1 point
which of the following compounds is most likely to undergo an sₙ1 reaction?
ch₃cl
(ch₃)₃cci
(ch₃)₂chci
c₂h₅cl

Explanation:

In an \(S_N1\) reaction, the rate - determining step is the formation of a carbocation intermediate. The stability of the carbocation plays a crucial role. The order of carbocation stability is \(3^{\circ}\gt2^{\circ}\gt1^{\circ}\gt\mathrm{CH}_3^+\).

• For \(\mathrm{CH}_3\mathrm{Cl}\), it would form a methyl cation (\(\mathrm{CH}_3^+\)), which is very unstable.
• For \((\mathrm{CH}_3)_3\mathrm{CCl}\), it forms a \(3^{\circ}\) carbocation (\((\mathrm{CH}_3)_3\mathrm{C}^+\)). The three methyl groups donate electron density inductively, stabilizing the positive charge.
• For \((\mathrm{CH}_3)_2\mathrm{CHCl}\), it forms a \(2^{\circ}\) carbocation (\((\mathrm{CH}_3)_2\mathrm{CH}^+\)), which is less stable than a \(3^{\circ}\) carbocation.
• For \(\mathrm{C}_2\mathrm{H}_5\mathrm{Cl}\) (ethyl chloride), it forms a \(1^{\circ}\) carbocation (\(\mathrm{C}_2\mathrm{H}_5^+\)), which is less stable than \(2^{\circ}\) and \(3^{\circ}\) carbocations.

Since \(S_N1\) reactions favor the formation of more stable carbocations, the compound that forms the most stable carbocation will most likely undergo an \(S_N1\) reaction.

Answer:

\((\mathrm{CH}_3)_3\mathrm{CCl}\)