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Title: HYDRATION OF BIS(PENTAMETHYLPHENYL)KETENE AND BISMESITYLKETENE LEADING TO ENE-1,1-DIOLS (ENOLS OF CARBOXYLIC-ACIDS)
Authors: ALLEN, BM ×
HEGARTY, AF
ONEILL, P
Nguyen, Minh Tho #
Issue Date: 1992
Publisher: ROYAL SOC CHEMISTRY
Series Title: Journal of the Chemical Society. Perkin transactions 2 issue:6 pages:927-934
Conference: date:NATL UNIV IRELAND UNIV COLL DUBLIN, DEPT CHEM, DUBLIN 4, IRELAND; UNIV LOUVAIN, DEPT CHEM, B-3001 LOUVAIN, BELGIUM
Abstract: The reaction of the sterically hindered diarylketenes (Ar = Me5C6 or 2,4,6-Me3C2H2) with water is pH independent over the range 1-9 and is not subject to strong buffer catalysis. The primary products formed are the corresponding ene-1,1-diols which result from addition across the C=O (rather than the C=C) of the ketene. These `enols of carboxylic acids' are relatively long lived owing to slow protonation of the beta-carbon (because of steric hindrance caused by the o-Me groups) and evidence for their structures in solution is presented. On attempted isolation of the ene-l,l -diols facile oxidation to a stable free radical, as well as ketonisation to the corresponding acids, occurs. Evidence is presented in terms of the large negative entropy of activation (ca. 200 J K-1 mol-1), solvent isotope effects and the absence of significant general-base catalysis, that (despite the sterically hindered nature of these ketenes) the characteristics of their hydration are typical of other ketenes and that this most likely involves an initial concerted reaction with a water oligomer. Updated ab initio calculations are also presented, which are consistent with this view.
ISSN: 0300-9580
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Quantum Chemistry and Physical Chemistry Section
× corresponding author
# (joint) last author

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