Stepwise mechanisms of the aminolyses of 4-Nitrophenyl and 2,4-Dinitrophenyl O-Ethyl Dithiocarbonates in aqueous Ethanol

✍ Scribed by Enrique A. Castro; Gabriel MuñOz; Mirtha Salas; Jose G. Santos

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 432 KB
• Volume: 27
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550271004

✦ Synopsis

Abstract

The reactions of the title substrates with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, at 25.0deg;C, ionic strength 0.2 M (maintained with KCl). Pseudo‐first‐order kinetics are found under amine excess. The order in amine obtained is one in the reactions of all amines. The Brönsted‐type plots for the overall second‐order rate coefficients are biphasic with slopes β~1~ = 0.3 (high p__K__~a~), β~2~ = 0.95 (low p__K__~a~) for the aminolysis of the 4‐nitro derivative, and β~1~ = 0.3 and β~2~ = 0.80 for the aminolysis of the dinitro compound; the p__K__~a~ values at the curvature center are p__K__ = 9.8 and 9.5, respectively. From a comparison of these p__K__ values with those found in the same reactions in water and the shapes of the Brönsted‐type plots, it is concluded that these reactions are stepwise, with the formation of a zwitterionic tetrahedral intermediate in the reaction pathway. © 1995 John Wiley & Sons, Inc.