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Lookup NU author(s): Peter Canning
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Arenediazonium tetrafluoroborates have been prepared and the kinetics of solvolysis have been investigated in water, trifluoroethanol, water-trifluoroethanol mixtures, hexafluoropropan-2-ol, trifluoroacetic acid, and ethanol by a UV method. A heterolytic mechanism involving short-lived aryl cations leads to products derived from nucleophilic capture of the aryl cations by solvent or a solute. Ionic solutes in aqueous trifluoroethanol and trifluoromethoxybenzene in trifluoroethanol have no kinetic effect and neither does replacement of the tetrafluoroborate counter-ion by chloride in trifluoroethanol. Rate constants for any one compound are not very solvent dependent, the reactions generally being characterised by high enthalpies of activation and appreciably positive entropies of activation. Compounds with 4-Cl, 4-F, 4-NO2, and 4-MeO substituents proved too unreactive for kinetic studies, but for different reasons. In ethanol, a radical reaction with characteristically different activation parameters competes with the heterolytic path and leads to hydrodediazoniation (reduction) by hydrogen atom abstraction from the CH2 group of ethanol.
Author(s): Canning PSJ, McCrudden K, Maskill H, Sexton B
Publication type: Article
Publication status: Published
Journal: Journal of the Chemical Society - Perkin Transactions 2
Year: 1999
Issue: 12
Pages: 2735-2740
Print publication date: 01/12/1999
ISSN (print): 0300-9580
ISSN (electronic): 1364-5471
Publisher: Royal Society of Chemistry
URL: http://dx.doi.org/10.1039/a905567c
DOI: 10.1039/a905567c
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