Heats of solution of aniline (AN), benzylamine (BA), ethyl-(EBS) and 2-phenylethyl benzenesulfonates (PEB) are calorimetrically measured in acetonitrile-methanol mixtures at 25.0 $^{circ}C$. The activation parameters, ${Delta}H^{ eq}$, ${Delta}S^{ eq}$ and ${Delta}G^{ eq}$, are determined for the reactions of EBS and PEB with AN and BA using the kinetic data at three temperatures. Calorimetric transfer enthalpies of initial state, ${delta}H_t^{0{ ightarrow}x})$(IS), and kinetically derived activation enthalpies, ${delta};{Delta}H^{ eq}$, in the MeCN-MeOH mixtures are combined to determine the transfer enthalpies of transition state, ${delta}H_t^{0{ ightarrow}x})$(TS); ${delta}H_t^{0{ ightarrow}x})$(IS) = ${delta}{Delta}H^{ eq};+;{delta}H_t^{0{ ightarrow}x}$(IS) The preferential solvation of anionic charge in the TS predicts a loose TS with a greater degree of bond cleavage for the reactions of PEB than for EBS, and also for the reactions with BA compared to the reactions with AN.