烷基对羰基反应性能影响的CNDO/2研究

A Study of the Effect of Alkyl Group on the Reactivity of Carbonyl Compounds by CNDO/2

对于碳-氧双键和亲核试剂的加成反应,由于负离子进攻为反应速度决定步骤,人们普遍认为羰基的反应性能主要取决于碳原子上的正电荷量,正电荷愈多亲核试剂愈易加成,全部反应也愈易进行。并认为酮的羰基的亲电能力比醛弱,这是由于酮的羰基和2个烃基相结合,如为烷基,具有给电子作用,则增加羰基碳原子电负性,降低其亲电能力。

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.