The reaction in which a nucleophile replaces already existing nucleophile in a molecule is called nucleophilic substitution reaction. Haloalkanes are substrate in these reactions. In this type of reaction, a nucleophile reacts with haloalkane (the substrate) having a partial positive charge on the carbon atom bonded to halogen. A substitution reaction takes place and halogen atom, called leaving group departs as halide ion. Since the substitution reaction is initiated by a nucleophile, it is called nucleophilic substitution reaction.

It is one of the most useful classes of organic reactions of alkyl halides in which halogen is bonded to sp3 hybridized carbon.

What is the product formed when tertiary butyl chloride reacts with boiling water? 

tert-Butyl alcohol

The correct answer is option 2. tert-Butyl alcohol

Tertiary butyl chloride reacts with boiling water to produce tert-Butyl alcohol.