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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 16, Number 1
BKCSDE 16(1)
January 20, 1995 

The Measurement of Transfer Enthalpy in Mixed Solvent (Part 2) Solvent Effects on Nucleophilic Substitution Reactions of Ethyl and 2-Phenylethyl Benzenesulfonates
Chul Huh, Hai Whang Lee*, Ikchoon Lee
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 ℃. The activation parameters, ΔH≠, ΔS≠ and Δ G≠, 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, δHt0→x(IS), and kinetically derived activation enthalpies, δΔH≠, in the MeCN-MeOH mixtures are combined to determine the transfer enthalpies of transition state, δ Ht0→x(TS); δHt0→x(TS) = δΔH≠ + δHt0→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.
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