用RHF从头计算法研究了氟代乙烷消除氟化氢反应的取代基效应．对所有构型均采用能量梯度法在3－21G基级水平上进行了优化，过渡态的构型用振动分析确认．计算结果表明，对所讨论的基团-F，-CH3，－CN，－NH2，在α位和β位取代，均对过渡态的结构有一定的影响，电荷分布表明，标题反应的过渡态为部分极化的四元环过渡态．－F在α位和β位的取代均使氟代烷1－2消除氟化氢反应的活化位垒升高，且前者的活化位垒高于后者；－CN在α位的取代使反应的活化位垒升高，在β位的取代使反应的活化位垒降低．－CH3和-NH2在α位的取代使反应的活化位垒降低，在β位的取代使反应的活化位垒升高，只是-NH2的效应强于-CH3．这些结果与由实验结果推测的结论一致表明，本消除反应与其它卤代烷的消除反应有显著的差别． The RHF ab initio method was used to investigate the substituent effect of fluoroethane in eliminating hydrogen fluoride. All configurations were optimized at the 3-21G level using the energy gradient method, and the configuration of the transition state was confirmed by vibration analysis. The calculated results show that the structures of the transition states are affected to some extent by the substitutions of -F, -CH3, -CN, -NH2 of the groups in question. The charge distributions show that the transition states of the title reactions For the partially polarized four-membered ring transition state. The substitution of -F in the α-position and β-position both raised the activation barrier for the reaction of fluoroalkane 1-2 to eliminate hydrogen fluoride, and the activation barrier of the former was higher than that of the latter. The substitution of -CN in the α-position resulted in the activation of the reaction Barrier rise, in the β-position of the reaction to reduce the activation barrier. Substitution of -CH3 and -NH2 in the α-position reduced the activation barrier of the reaction. The substitution at the β-site increased the activation barrier of the reaction, but the effect of -NH2 was stronger than that of -CH3. These results, in agreement with the results speculated by the experimental results, show that there is a significant difference between the elimination reaction and the elimination reaction of other alkyl halides.