Organic reaction: SN1 reaction and SN2 reaction

SN1 vs. SN2

Nucleophilic substitution reactions are very important reactions of alkyl halide. There can be two pathways:

  1. Unimolecular nucleophilic substitution, SN1
  2. Bimolecular nucleophilic substitution, SN2.

Whether an alkyl halide will undergo an SN1 or an SN2 reaction depends upon a number of factors. Here are some:

Let’s consider all the factors:

The Mechanism

SN1 – a stepwise process in which a loss of the leaving group to form a carbocation intermediate followed by a nucleophilic attack.

SN2 – a concerted one-step process in which the addition of nucleophiles and the loss of the leaving group occur simultaneously.

Rate Law

SN1 – Unimolecular means that only one molecule (substrate) affects the rate of the reaction. This will be the step in which the substrate is involved. And this is the first step, the formation of a carbocation.