Question

What is a substitution reaction? Give an example.

Answer 1

Substitution reaction takes place in organic chemistry. In this type of reaction an incoming species replaces the existing species in the substrate (reactant is known as the substrate on which the reaction is taking place). In this reaction one group in a compound is replaced by the incoming group from other species.

Complete answer:
In organic chemistry, there are mainly two types of reactions, one is substitution reaction and the other one is addition reaction. We will explain about substitution reactions in detail.
So, substitution reaction takes place in organic chemistry and in this type of reaction an incoming species replaces the existing species in the substrate (reactant is known as substrate on which the reaction is taking place).
Therefore, in the substitution reaction, the functional group of one compound is replaced or substituted by the functional group of another compound.
Let us take an example of substitution reaction which is given as follows:
$C{H_3}C{H_2}Br + {K^ + }C{N^ - } \to C{H_3}C{H_2}CN + KBr$
In the above reaction, we can see that bromide ion $(B{r^ - })$ is present in the substrate. It was treated with potassium cyanide in which the cyanide ion behaved as the incoming nucleophile and replaced or substituted the bromide ion in the substrate.

Note:
Now we know about the substitution reactions in detail. There are two types of substitution reactions which are ${S_N}1$ and ${S_N}2$ . There are some differences between these two reactions such as ${S_N}1$ shows retention of configuration in the product while ${S_N}2$ reaction shows inversion of configuration in the product. ${S_N}1$ is a unimolecular reaction while ${S_N}2$ is a bimolecular reaction.