4-Acetylbenzaldehyde, $p - CH X_{3} CO - C X_{6} H X_{4} - CHO$ , is treated in sequence with (i) one equivalent of ethylene glycol, dry $HCl$ ; (ii) $CH X_{3} MgBr$ (1 equiv), dry ether; (iii) dilute $H X_{3} O X^{+}$ . The final product is

Answer: D

The aldehyde, which is more reactive than the ketone toward acetal formation, is protected as the cyclic acetal.

CH X_{3} MgBr

then adds to the ketone to give a tertiary alkoxide,

- C (CH X_{3}) X_{2} OMgBr

. Aqueous acid removes the acetal, giving

p - OHC - C X_{6} H X_{4} - C (CH X_{3}) X_{2} OH