How would you differentiate between `S_(N)1 and S_(N)2` mechanism of substitution reactions? Give one example of each.

Explanation

In `S_(N)1` mechanism of substitution reaction, the rate of reaction depends upon the concentration of only one reactant, e.g, in the reaction between tert-butyl bromide and hydroxide ion to form tert-butyl alcohol, rate of reaction depends only on the concentration of tert-butyl bromide.
`(CH_(3))_(3)C-Br+OH^(-) to (CH_(3))_(3)C-OH +Br^(-) `
It involves the formation of carbocation intermediate and racemisation.
In `S_(N)2` mechanism of substitution reaction, the rate of reaction depends upon the concentration of both the reactants, e.g. in the reaction between methyl chloride and hydroxide ion to form methanol, rate of reaction depends on the concentration of both the reactants.

It involves the formation of transition state and inversion (Walden inversion) of configuration.