Discuss the reaction mechanisms with differences in them when `CH_(3) Cl `and `(CH_(3))_(3) C Cl` are separately reacted with aqueous NaOH .

Explanation

Methyl chloride `(CH_(3) Cl)` undergoes alkaline hydrolysis by the `S_(N) 2` mechanism .
`underset("(substance)")underset("Methyl chloride ") (CH_(3) Cl) + underset("(from NaOH)")underset("Nucleophile")(OH^(-)) to underset("(substituted compound)")underset("Methyl alcohol")(CH_(3)OH) + underset("Leaving group")(Cl^(-))`
The mechanistic course of the nucleophile `OH^(-)` displaces `Cl^(-)` from the backside ( a backside attack) may be shown as follows :

This backside attack is feasible as there is no steric hindrance at the reacting side .
The rate of the reaction depends on the concentration of both the substrate and the nucleophile , i.e, rate = `k xx [CH_(3) Cl] xx [OH^(-)]`
Therefore both the substrate and the nucleophile are involved in the rate determining step ( the only step here) of the reaction , i.e., the reaction is a nucleophilic biomolecular substitution reaction ( `S_(N) 2)`
teri-butyl chloride `(MeC Cl)` , on the other hand , undergoes alkaline hydrolysis by the `S_(N) 1` mechanism .
`underset("(substrate)") underset("teri- butyl chloride")((CH_(3))_(3)) C Cl + underset("(from NaOH)")underset("Nucleophile")(OH^(-)) to underset("(substituted compound)")underset("alcohol")underset("tert-butyl")((CH_(3))_(3) )COH + underset("Leaving group")(Cl^(-))`
The mechanism of the reaction (a two - step process) may be shown as follows :

The subtrate dissociates to form a stable carbocation.
Second step :

The rate of the reaction depends on the concentration of the substrate , i.e.,
rate `= k xx [(CH_(3))_(3) C Cl]`
Therefore , only the substrate is involved in the rate - determining step ( the first step) of the reaction i.e., the reaction is a nucleophilic unimolecular substitution reaction . `(S_(N) 1)` .