An investigation of the reduction in aqueous acetonitrile of 4-methoxybenzenediazonium ion by the tetrakis(acetonitrile)Cu(I)cation catalysed by hydrogenphosphate dianion

Peter Hanson, Alec B. Taylor, Paul H. Walton, Allan W. Timms

Research output: Contribution to journalArticlepeer-review

Abstract

In aqueous acetonitrile containing a phosphate buffer, 4-methoxybenzenediazonium ion is reduced by one or more of the partially aquated cations derived from tetrakis(acetonitrile) Cu(I) cation in this medium. Investigation of the reaction mechanism indicates the rate determining step to be the association of the diazonium ion with the hydrogenphosphate dianion to give an adduct which then undergoes reduction by Cu(I). The reaction gives a range of products which have been identified and quantified by GC. One of these, 4-methoxyphenol was unexpected in the reducing conditions; its presence could be explained by the disproportionation of a 4-methoxyphenylcopper(II) complex giving bis(4-methoxyphenyl)copper(III) which reacts with water to produce the phenol and an equivalent amount of methoxybenzene. A scheme is proposed which accounts for all the observed products and computer modelling gives a satisfactory description of the distributions of the five major products as functions of the relative proportions of the reactants for dilute conditions and those where the reductant is in excess. When the diazonium ion is in excess, the behaviour of the model and the experimental reactant accountability suggest the occurrence of additional reactions which give products unobserved by GC.

Original languageEnglish
Pages (from-to)679-698
Number of pages20
JournalOrganic and Biomolecular Chemistry
Volume5
Issue number4
DOIs
Publication statusPublished - 2007

Keywords

  • ELECTRON-SPIN-RESONANCE
  • ALIPHATIC FREE-RADICALS
  • PULSE-RADIOLYSIS
  • SANDMEYER REACTIONS
  • SOLVATOCHROMIC PARAMETERS
  • ARENEDIAZONIUM IONS
  • DIAZONIUM IONS
  • ARYL RADICALS
  • POTENTIOMETRIC SENSORS
  • ARYLDIAZENYL RADICALS

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