The reactions of methyl 4-nitrophenyl carbonate (MNPC) with a series of secondary alicyclic amines (SAA) and quinuclidines (QUIN), methyl 2,4-dinitrophenyl carbonate (MDNPC) with QUIN and 1-(2-hydroxyethyl)piperazinium ion (HPA), and phenyl 2,4-dinitrophenyl carbonate (PDNPC) with SAA are subjected to a kinetic investigation in aqueous solution, at 25.0 °C and an ionic strength of 0.2 M. By following spectrophotometrically the nucleofuge release (330-400 nm) under amine excess, pseudo-first-order rate coefficients (k[sub obsd]) are obtained. Plots of k[sub obsd] vs [amine] at constant pH are linear, with the slope (k[sub N]) being pH independent. The Brönsted-type plot (log k[sub N] vs amine pK[sub a]) for the reactions of SAA with MNPC is biphasic with slopes β[sub 1] = 0.3 (high pK[sub a] region) and β[sub 2] = 1.0 (low pK[sub a] region) and a curvature center at pK[sub a][sup 0] = 9.3. This plot is consistent with a stepwise mechanism through a zwitterionic tetrahedral intermediate (T[sup ±]) and a change in the ratedetermining step with SAA basicity. The Brönsted plot for the quinuclidinolysis of MNPC is linear with slope β[sub N] = 0.86, in line with a stepwise process where breakdown of T[sup ±] to products is rate limiting. A previous work on the reactions of SAA with MDNPC was revised by including the reaction of HPA. The Brönsted plots for the reactions of QUIN and SAA with MDNPC and SAA with PDNPC are linear with slopes β = 0.51, 0.48, and 0.39, respectively, consistent with concerted mechanisms. Since quinuclidines are better leaving groups from T[sup ±] than isobasic SAA, yielding a less stable T[sup ±], it seems doubtful that the quinuclidinolysis of PDNPC is stepwise, as reported. [ABSTRACT FROM AUTHOR]