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Published on: March 2, 2012
Analysis of the nucleophilic solvation effects in isopropyl chlorothioformate solvolysis
Malcolm J D'Souza1, Brian P Mahon, Dennis N Kevill
1Department of Chemistry, Wesley College, 120 N. State Street, Dover, DE 19901-3875, USA.
Abstract:
Correlation of the solvent effects through application of the extended Grunwald-Winstein equation to the solvolysis of isopropyl chlorothioformate results in a sensitivity value of 0.38 towards changes in solvent nucleophilicity (l) and a sensitivity value of 0.72 towards changes in solvent ionizing power (m). This tangible l value coupled with the negative entropies of activation observed indicates a favorable predisposition towards a modest rear-side nucleophilic solvation of a developing carbocation. Only in 100% ethanol was the bimolecular pathway dominant. These observations are very different from those obtained for the solvolysis of isopropyl chloroformate, where dual reaction channels were proposed, with the addition-elimination reaction favored in the more nucleophilic solvents and a unimolecular fragmentation-ionization mechanism favored in the highly ionizing solvents.
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