Original scientific paper

Rates and Mechanism of Solvolysis of Arenediazonium Ions in Aqueous Trifluoroethanol

H. Maskill ; Chemistry Department, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, United Kingdom
Katharine McCrudden ; Chemistry Department, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, United Kingdom

Abstract

Rates of solvolysis of benzenediazonium tetrafluoroborate and six of its methyl-substituted analogues have been measured in water, trifluoroethanol, and mixtures of the two over a range of temperatures. The enthalpies of activation are uniformly high and show only a low dependence upon the solvent composition. The entropies of activation are all appreciably positive and also show only small variations with the composition of the solvent. Methyl substituents in ortho and meta positions are modestly rate enhancing; a para- methyl is rate retarding. The results are discussed in terms of a mechanism involving an initial fragmentation of the diazonium ion into a phenyl cation - nitrogen molecule complex which then undergoes rate-limiting dissociation followed by product-forming capture of the phenyl cation by solvent molecules.

Keywords

Hrčak ID:

137117

URI

https://hrcak.srce.hr/137117

Publication date:

15.10.1992.

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