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RISS 인기검색어
- 검색키워드
- 저자 : A. Shunmugasundaram* (검색결과 2 건)
- 무료
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P. A. Sarathi,C. Gnanasekaran,A. Shunmugasundaram* 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.4
Nucleophilic addition reaction of benzenethiols (PhSH) to 1-(2-nitrovinyl) benzenes (b NS) in the presence of triethylamine (TEA) has been studied in acetonitrile at 25℃. The rate is first order with respect to [PhSH], [TEA] and [b NS]. The reaction is found to proceed with the formation of ion-pair between benzenethiol and TEA. A suitable mechanism with the formation of an adduct between ion-pair and substrate in a slow step followed by its rearrangement to 1,2-addition product in a fast step has been proposed and corresponding rate law derived. From the rate law, the rate constants for the interaction between ion-pair and b NS have been evaluated. Interestingly, in both para-substituted substrates and benzenethiols the rate increases with the electron-withdrawing power of the substituents. The positive sign of r x in benzenethiols has been explained. The magnitude of cross-interaction constant, r xy is small (0.08). The magnitude of the Hammett r x values is higher than that of the Bronsted, b x values for benzenethiols. The kinetic isotope effect, kH/kD, is found to be greater than unity. A suitable transition state with simultaneous formation of Cb -H and Ca -S bonds involving the ion-pair and b NS in a single concerted step has been proposed to account for these observations.
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Sarathi, P.A.,Gnanasekaran, C.,Shunmugasundaram, A. Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.4
Nucleophilic addition reaction of benzenethiols (PhSH) to 1-(2-nitrovinyl) benzenes ($\beta$ NS) in the presence of triethylamine (TEA) has been studied in acetonitrile at 25 ${^{\circ}C}$. The rate is first order with respect to [PhSH], [TEA] and [$\beta$ NS]. The reaction is found to proceed with the formation of ion-pair between benzenethiol and TEA. A suitable mechanism with the formation of an adduct between ion-pair and substrate in a slow step followed by its rearrangement to 1,2-addition product in a fast step has been proposed and corresponding rate law derived. From the rate law, the rate constants for the interaction between ion-pair and $\beta$NS have been evaluated. Interestingly, in both para-substituted substrates and benzenethiols the rate increases with the electron-withdrawing power of the substituents. The positive sign of $\rho_x$ in benzenethiols has been explained. The magnitude of cross-interaction constant, $\rho_{xy}$ is small (0.08). The magnitude of the Hammett $\rho_x$ values is higher than that of the Bronsted, $\beta_x$ values for benzenethiols. The kinetic isotope effect, $k_H/k_D$, is found to be greater than unity. A suitable transition state with simultaneous formation of $C_\beta$ -H and $B_\alpha$ -S bonds involving the ion-pair and $\beta$NS in a single concerted step has been proposed to account for these observations.
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