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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 19, Number 2
JKCSEZ 19(2)
April 20, 1975 

Substituent Effects on the Leaving Groups in Benzyl Arenesulfonates

Benzyl Arenesulfonate의 이탈기의 치환기효과에 관한 연구 (제1보)
Soo Dong Yoh

Benzyl arenesulfonate와 피리딘과의 아세톤 용매중에서의 반응속도를 측정하였다. Benzyl arenesulfonate의 이탈기의 치환기효과는 p-MeO기 및 p-NO2기를 제외하고는 Hammett 식에 잘 적용되었으며, 전자끄는기는 반응속도를 증가시켰다. 이탈기의 치환효과는 벤질탄소에 아민이 친핵적으로 공격하여 전이상태에서 치환기의 전자끄는 능력이 C-N 결합의 형성과 C-O결합의 쪼개짐에 변화를 주고 있다는 사실로서도 설명이 되어진다. 치환기효과는 benzyl p-bromobenzeneslfonate가 benzyl p-nitrobenzenesulfonate보다 N-C결합이 tight 한 전이상태의 구조를 가지고 있음을 말해주며 이는 결합의 형성과 쪼개짐에 있어 Thornton의 SN2전이상태 구조의 예상과도 잘 부합된다.

Determination has been made of the kinetics of the reaction of benzyl arenesulfonates with pyridine in acetone. The substituent effects of the leaving groups in benzyl arenesulfonates are correlated by Hammett equations, with the exception of p-MeO and p-NO2 groups, where the electron attracting substituents in the benzyl arenesulfonate increase the rate. The substituent effects of the leaving groups are as expected due to the nucleophilic attack of amine on the benzyl carbon atom. This can be understood in terms of changes in bond formation (C-N) and bond breaking (C-O) in the transition state with charges in electron-attracting ability of the substituents. The predicted substituent effects may indicate a small increase in bond formation and thus a tighter transition state, in benzyl p-bromobenzene sulfonate than in benzyl p-nitrobenzenesulfonate. Predicting made by Thornton concerning the substituent effects on SN2 transition state structures agrees with the changes in bond formation and bond breaking.

116 - 122
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