# Explain nucleophilic substitution of alkyl halides?

Jan 10, 2015

Nucleophilic substitution of alkyl halides is the substitution of the halogen by another group called a nucleophile.

In most of the alkyl halides, the C-X bond is polar.

That gives the α carbon a partial positive charge

The positive charge makes that carbon susceptible to attack by a nucleophile.

In one scenario, called the $\text{S"_"N} 2$ mechanism, the halide leaves at the same time as the nucleophile attacks.

In a different scenario, the $\text{S"_"N} 1$ mechanism, the halide ion leaves first, forming a carbocation.

The nucleophile attacks the carbocation in a second step, forming the product.

Here's a video on the nucleophilic substitution of alkyl halides.