The effect of acyl substituents on the α-effect: contrasting α-effect profiles for reactions of 4-nitrophenyl substituted benzoates with neutral and anionic nucleophiles

The magnitude of the α-effect for reactions of 4-nitrophenyl substituted benzoates with a pair of anionic nucleophiles is independent of the electronic nature of the acyl substituent, while the one for the corresponding reactions with a pair of neutral nucleophiles increases as the acyl substituent changes from a strong electron withdrawing substituent to electron donating ones.