Abstract: According to the results of CNDO/2, this paper considers that the positive charge of the car-boxylic carbon increases under the influence of alkyl group. This is in agreement with the rule that alkyl groups have the a-electron repulsing effect. The frontier orbital method is used to explanin that alkyl group reduces reactivity of carbonyl group.

Key words: Inductive effect of alkyl group, Reactivity of carbonyl group, Frontier orbital method