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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 25, Number 1
JKCSEZ 25(1)
February 20, 1981 

 
Title
Nucleophilic Displacement at Sulfur Center (ⅩⅢ). Solvolysis of para-Substituted Benzenesulfonyl Chlorides in MeOH-MeCN Mixtures

황의 친핵성 치환반응 (제13보). 메탄올-아세토니트닐계에서의 파라치환 염화벤젠술포닐의 가용매 분해반응
Author
Ikchoon Lee, In Sun Koo

이익춘, 구인선
Keywords
Abstract
p-CH3, p-H, p-Cl 및 p-NO2기로 치환된 염화벤젠술포닐의 가용매분해반응을 MeOH-MeCN혼합용매계에서 연구하였다. 반응속도는 p-NO2 > p-CH3 > p-H > p-Cl의 순위로서 비직선 Hammett관계를 나타내어 SN1-SN2경계반응메카니즘으로 반응함을 알았다. 반응성은 모든 경우 약 90∼95% 메탄올용액에서 최대였으나, fi = k1/ki로 정의되는 각 기질의 메탄올 단위체 선택성(monomer selectivity)은 80% 메탄올 용액에서 최대이며, 그 크기 순위는 p-NO2 > p-Cl > p-H > p-CH3로서 전이상태 구조가 tight할 수록 fi값이 크며 메탄올 단위체를 예민하게 선별 감지함을 알 수 있었다.

Solvolysis of p-CH3, p-H, p-Cl and p-NO2-benzenesulfonyl chlorides have heen studied in MeOH-MeCN mixtures. A nonlinear Hammett plot with a ratio order of p-NO2 > p-CH3 > p-H > p-Cl was obtained; the reaction was thought to proceed by an SN1-SN2 borderline mechanism. In all cases the reactivity was a maximum at 90∼95%(v) methanol, whereas methanol monomer selectivity defined as fi = k1/ki (k1; observed pseudo-first order rate constant: ki; hypothetical rate constant for MeOH solution having the same polymer structure as in the pure MeOH) was a maximum at 80% methanol with a decreasing order of fi as p-NO2 > p-Cl > p-H > p-CH3. This was interpreted as the decrease in tightness of transition state; the larger the fi, the tighter is the MeOH attached to the substrate, and hence the more susceptible the substrate becomes to the approaching monomer methanol.

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