Q1(d). Para-alkyl effects on benzyl solvolysis

Answer in brief

The intended hyperconjugative comparison predicts A solvolyses faster than B.

Key points

• Ionization develops a benzyl cation whose positive charge is delocalized to the ortho and para ring positions.
• The para methyl group has three alpha C–H bonds available for favourable hyperconjugative donation into the electron-deficient aromatic system.
• The carbon directly attached to the ring in tert-butyl has no C–H bond. Its inductive donation does not reproduce the same methyl C–H hyperconjugation.
• Thus an order based only on the greater alkyl substitution of tert-butyl is inappropriate here.