Question

$S_{N}1$ reaction is favoured by:

• A. Bulky groups on the carbon atom attached to halogen atom
• B. Small groups on the carbon attached to halogen atom.
• C. Non-polar solvents
• D. None of the above

Answer 1

The correct option is A Bulky groups on the carbon atom attached to halogen atom

$S_{N}1$ mechanism proceeds through carbocation formation and as stability of carbocation increases, it favours $S_{N}1$ mechanism and as we add bulky group to carbon attached with halogen, carbocation formed will become more stable due to +I effect of bulky alkyl group so it favours $S_{N}1$ mechanism.
Polar solvents favours $S_{N}1$ reaction because it solvate the nucleophile and make it less nucleophilic.