The further development of a convenient, conductimetric method for studying the rates of relatively fast solvolytic reactions in highly aqueous media is described. Rate and product data are reported for solvolyses of benzoyl chloride at 25 "C in water and in binary aqueous mixtures with acetone, ethanol, methanol, trifluoroethanol, and hexafluoropropan-2-01. Comparison of these kinetic data with ratedata for the s N 1 model, 1 -adamantyl chloride, reveals sensitivity to solvent nucleophilicity even for highly aqueous media. In contrast with other nucleophilically solvent-assisted processes, the solvent effects are not satisfactorily correlated by one linear free energy relationship. Gas-phase thermochemical data show the feasibility of a direct heterolytic cleavage of the C-CI bond in benzoyl chloride. Rate-product correlations for hydrolysis and aminolysis in 50% w / w acetone-water are observed, providing that allowance is made for the medium effect of the added o-nitroaniline. These results are consistent with an sN2 mechanism, not SN1 and/or ion-pair mechanisms previously discussed. Another pathway, dominant in less aqueous media, is much less sensitive to changes in solvent ionizing power, consistent with earlier proposals for a carbonyl addition-elimination mechanism.
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