Abstract
The specific rates of solvolysis of benzyl fluoroformate have been measured inseveral hydroxylic solvents at 25.0 °C. For methanolysis, the solvent deuterium isotopeeffect and activation parameters were determined and activation parameters were alsodetermined for solvolyses in ethanol and 80% ethanol. For several of the binary hydroxylicsolvents, measurement of product ratios allowed selectivity values to be determined. Anextended Grunwald–Winstein treatment of the data led to sensitivities to changes in solventnucleophilicity and ionizing power. Comparison with previously determined specific ratesfor solvolysis of the chloroformate gave fluorine/chlorine rate ratios greater than unity. Allof the determinations made were consistent with an addition–elimination (association–dissociation) mechanism, with addition rate-determining.
Highlights
Chloroformate esters with primary alkyl groups solvolyze in most of the commonly studied solvents by an addition–elimination mechanism with the addition step being rate-determining
For ethanol and 80% ethanol, specific rates were determined at two additional temperatures, and activation parameters were calculated
We have extended the previous study [4] of the solvolyses of benzyl chloroformate to the fluoroformate
Summary
Chloroformate esters with primary alkyl groups solvolyze in most of the commonly studied solvents by an addition–elimination mechanism with the addition step being rate-determining. In solvents of very low nucleophilicity and very high ionizing power is an ionization mechanism observed. For methyl chloroformate solvolysis [1] the ionization mechanism was observed only in 1,1,1,3,3,3-. 2006, 7 hexafluoro-2-propanol (HFIP)–water mixtures with at least 90% HFIP content. The ionization range was larger for ethyl [2] and n-propyl [3] chloroformates, and ionization was indicated with up to 50% water content in HFIP–H2O and with up to 10% water content in 2,2,2-trifluoroethanol (TFE)–H2O mixtures
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