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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 35, Number 1
BKCSDE 35(1)
January 20, 2014 

 
Title
Product-Rate Correlations for Solvolyses of 2,4-Dimethoxybenzenesulfonyl Chloride
Author
Soo Ryeon Kim, Hojune Choi, Jong Keun Park, In Sun Koo*, Han Joong Koh*
Keywords
Extended Grunwald-Winstein equation, SN2 mechanism, Solvent kinetic isotope effect, Product selectivity, Third-order rate constant
Abstract
The solvolysis rate constants of 2,4-dimethoxybenzenesulfonyl chloride (1) in 30 different solvents are well correlated with the extended Grunwald-Winstein equation, using the NT solvent nucleophilicity scale and YCl solvent ionizing scale, with sensitivity values of 0.93 ± 0.14 and 0.65 ± 0.06 for l and m, respectively. These l and m values can be considered to support a SN2 reaction pathway. The activation enthalpies (H ) were 12.4 to 14.6 kcal·mol1 and the activation entropies (S) were 15.5 to 32.3 cal·mol1·K1, which is consistent with the proposed bimolecular reaction mechanism. The solvent kinetic isotope effects (SKIE) were 1.74 to 1.86, which is also in accord with the SN2 mechanism and was possibly assisted using a general-base catalysis. The values of product selectivity (S) for solvolyses of 1 in alcohol/water mixtures was 0.57 to 6.5, which is also consistent with the proposed bimolecular reaction mechanism. Third-order rate constants, kww and kaa, were calculated from the rate constants (kobs), together with kaw and kwa calculated from the intercept and slope of the plot of 1/S vs. [water]/[alcohol]. The calculated rate constants, kcalc (kww, kaw, kwa and kaa), are in satisfactory agreement with the experimental values, supporting the stoichiometric solvation effect analysis.
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51 - 56
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