Abstract

The reactions of secondary alicyclic (SA) amines with 4-nitrophenyl 2,4-dinitrophenyl carbonate (4) and bis(2,4-dinitrophenyl) carbonate (5) are subjected to a kinetic investigation in 44 wt% ethanol-water, at 25.0C, ionic strength 0.2 M. The reactions are examined by monitoring spectrophotometrically the appearance of 2,4-dinitrophenoxide. Under conditions of excess amine, pseudo-first-order rate coefficients (k obsd) are found. Plots of kobsd against free amine concentration at constant pH are linear with k N as slope. The Brønsted-type plots (log k N vs amine pK a) obtained are also linear with slopes 0.51 and 0.48 for the aminolysis of 4 and 5, respectively. These slope values are in accordance with concerted (one step) mechanisms. The absence of a Brønsted break at the predicted pK a for hypothetical stepwise mechanisms confirms the concerted nature of these reactions. ©ARKAT USA, Inc.