The reactions of the title substrate with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, 25.0°C, and ionic strength 0.2 M (KC1). The Bronsted-type plot (log k~ vs. pKa of the amine, where k~ is the second-order rate coefficient) obtained is linear with slope p = 0.53, which indicates a concerted mechanism. The predicted Bronsted break for a hypothetical stepwise mechanism is pK,O = 8.7, which was not observed (pKa range of amines: 6-11). The same reaction in water is stepwise, which shows that the tetrahedral intermediate found in water is much destabilized by the change of solvent from water to aqueous ethanol.

The reactions of the title substrates with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, a t 25.0°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 Bronsted-type plots for the overall second-order rate coefficients are biphasic with slopes p1 = 0.3 (high pK,), p2 = 0.95 (low pX,) for the aminolysis of the 4-nitro derivative, and p1 = 0.3 and pz = 0.80 for the aminolysis of the dinitro compound; the pK, values at the curvature center are pK: = 9.8 and 9.5, respectively. From a comparison of these pK; values with those found in the same reactions in water and the shapes of the Bronsted-type plots, it is concluded that these reactions are stepwise, with the formation of a zwitterionic tetrahedral intermediate in the reaction pathway. 0 1995 John Wiley & Sons, Ine.

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