20351-75-1Relevant articles and documents
Kinetics and mechanism of the reactions of O-aryl S-(4-nitrophenyl) dithiocarbonates with anilines in aqueous ethanol
Castro, Enrique A.,Gazitua, Marcela,Santos, Jose G.
scheme or table, p. 176 - 180 (2010/08/20)
The reactions of O-(4-methylphenyl) S-(4-nitrophenyl) dithiocarbonate and O-(4-chlorophenyl) S-(4-nitrophenyl) dithiocarbonate with a series of anilines are subjected to a kinetic investigation in 44wt% ethanol-water, at 25.0 °C and an ionic strength of 0.2 M. The reactions are followed spectrophotometrically at 420nm (appearance of 4-nitrobenzenethiolate anion). Under excess amine, pseudo-first-order rate coefficients (kobs) are found. For the reactions of both substrates with anilines, plots of k obs versus free amine concentration at constant pH are nonlinear upwards, according to a second-order polynomial equation. This kinetic behavior is in agreement with a stepwise mechanism consisting of two tetrahedral intermediates, one zwitterionic (T±) and the other anionic (T-), with a kinetically significant proton transfer from T ± to an aniline to yield T-. The rate equation was derived from the proposed mechanism. By nonlinear least-squares fitting of the rate equation to the experimental data, values of the rate micro-coefficients involved in both steps were determined. Copyright
Aminolysis of aryl chlorothionoformates with anilines in acetonitrile: Effects of amine nature and solvent on the mechanism
Oh, Hyuck Keun,Ha, Joo Suk,Sung, Dae Dong,Lee, Ikchoon
, p. 8219 - 8223 (2007/10/03)
The aminolysis of aryl chlorothionoformates (7, YC6H 4OC(=S)Cl) with anilines (XC6H4NH2) in acetonitrile at 5.0 °C has been investigated. The rates are slower than those for the corresponding reactions of aryl chloroformates (6, YC 6H4OC(=O)Cl). This rate sequence is a reverse of that for alkyl chloroformates (1 4) in water, for which rate-limiting formation of a tetrahedral intermediate, T±, is predicted. On the basis of the large negative cross-interaction constant, ρXY = -0.77, failure of the reactivity-selectivity principle, normal kH/k D values involving deuterated nucleophiles (XC6H 4ND2), and low ΔH≠ with large negative ΔS≠ values, a concerted mechanism with a four-membered hydrogen bonded cyclic transition state (11) is proposed for the title reaction series. It has been shown that the solvent change from water to acetonitrile for the aminolysis of 6 and 7 causes a mechanistic change from stepwise to concerted.
