Correlation of the rates of solvolysis of acetic p ‐toluenesulfonic anhydride (acetyl p ‐toluenesulfonate) and a comparison with acetyl halides

The specific rates of solvolysis of acetyl p ‐toluenesulfonate have been measured by a rapid‐response conductivity technique at temperatures in the temperature range of −10 to −55 °C. For 13 solvents at −39.6 °C, an extended Grunwald–Winstein equation correlation led to sensitivities to changes in solvent nucleophilicity of 0.56 and to changes in solvent ionizing power of 0.61. In 89.1% acetone at −20 °C, the comparison with acetyl bromide solvolysis led to a k OTs / k Br ratio of 1.4. In methanol and methanol‐ d at −39.6 °C, the solvent deuterium isotope effect k MeOH / k MeOD is 0.99. These results are consistent with an S N l reaction with appreciable nucleophilic solvation or an S N 2 reaction with a loose transition state. These two approaches lead to similar structures for the transition state. A solution of the acetyl p ‐toluenesulfonate was conveniently prepared by the rapid reaction of acetyl chloride with silver p ‐toluenesulfonate in acetonitrile. Copyright © 2013 John Wiley & Sons, Ltd.