Kinetics and mechanism of the alcoholyses of ethyl fluorosulphate

Abstract

The alcoholyses of ethyl fluorosulphate in methyl, ethyl, n‐propyl, isopropyl, n‐butyl, isobutyl, tert‐butyl and n‐pentyl alcohols in the initial concentrations and temperature ranges of (1–10) 10−3 M and − 15.00 to 22.00 °C, respectively, were studied. The reactions follow pseudo‐first‐order kinetic laws up to at least ca 75 per cent ester conversions. At 10°C the experimental rate constant for ethanolysis is similar to that of ethyl triflate but much smaller than for its hydrolysis. The reactivity of the ester is ca 104–105 times higher than that of alkyl halides and benzenesulphonates. In alcohol–benzene and alcohol–acetone mixtures the ΔH≠ and ΔS≠ activation parameters are only slightly affected by the media composition. The effect of the ‘lyate ion’ on the kinetics of these reactions were investigated and the effects of changes in the dielectric constant of the media were evaluated. It is concluded that the alcoholyses of the ester fulfil the requirements for predominant SN2‐type mechanism, where the reaction ground states are more polar than the corresponding transition states.