Product-Rate Correlations for Solvolyses of 2,4-Dimethoxybenzenesulfonyl Chloride

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, 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.

Mechanistic studies of the solvolysis of alkanesulfonyl and arenesulfonyl halides

“…Consistent with the bimolecular nature of the solvolyses of alkanesulfonyl chlorides and arenesulfonyl chlorides [49,[55][56][57][58][59][60][61][62][63][64][65][66][67], poor correlations are obtained when the logarithmic rate data are correlated against only Y Cl values, using Equation 1.…”

“…In Table 2 are assembled the calculated l, m, and c values (Equation 2), obtained from correlations in 19-43 solvents for thirteen sulfonyl chlorides (structures presented in Table 1), containing very simple to fairly complex substrates, which can be considered as aryl, arylalkyl, arylalkenyl, or heteroaryl sulfonyl chlorides. (1 through 6 and 8 through 14 in Table 1 and these identifiers are used, and references [49,[56][57][58][59][60][61][62][63][64][65][66]68]).…”