摘要
本文用MINDO/3方法研究了烯烃RCH=CH_2(R=H,CH_3,CHO和NO_2)与过氧甲酸反应的机理.研究结果表明,RCH—CH_2与过氧甲酸反应是亲电反应,在加热条件下较容易进行.乙烯与过氧甲酸反应的过渡态具有局部对称结构;若R为取代基时,这种对称性不复存在,对于R为给电子基,过氧基的氧偏向与取代基相连的乙烯碳原子,R为吸电子基,过氧基氧偏向乙烯的另一碳原子;取代基的给、吸电子能力越强,过渡态偏离对称结构越显著,活化势垒降低或升高也越大.
MINDO/3 MO method has been used to study the reactions of peroxyformio acid with ethylene and substitued ethylenes. The results calculated show that the reactions of RCH=CH_2 with peroxyformic acid are electrophilic reactions. The activation energy decreases with R being electron donating substituent, while it increases by electron withdrawing substituents. Besides, when R=H, the transition structure (TS1) possesses local symmetry, as for R=CH_3, CHO, NO_2, this symmetry no more exists. The activation energy E^a for various substituents can be estimated by the following equation: E^2=-80.6△q+80.6kJ/mol where △q equals the difference of net charges between the two ethylenic carbon atoms.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1991年第6期540-545,共6页
Acta Chimica Sinica
基金
国家自然科学基金资助的课题
