Question

I need a clear detailed explanation of the answer of this question please

Q- Secondary and primary alkyl bromides do not usually undergo S_N1 and E1 reactions. Why? Vinyl and aryl bromides are even less prone to undergo these reactions. Why?

Answer 1

The main factor one needs to keep in mind while working with SN1 and E1 reactions is to consider the stability of the generated carbocation intermediates.

The general stability order for carbocations: 1^o < 2^o < 3^o

Now, coming to the secondary and primary alkyl bromides, which generate secondary and primary carbocations, respectively in the SN1 and E1 reactions, which are comparatively less stable. Hence, they do not usually undergo these reactions.

Now, coming to the vinyl and aryl bromides, which can't generate the sp²-carbocations (vinyl and aryl cations) which are highly unstable. Hence, they even less prone to undergo SN1 and E1 reactions.