The chemistry of vitamin B12. Part 21. Ethynylaquocobinamide: Novel reaction of diaquocobinamide with acetylene catalysed by copper ions

David A. Baldwin, Eric A. Betterton, John M. Pratt

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Copper ions catalyse the reaction of diaquocobinamide with acetylene in aqueous solution at room temperature to give ethynylaquocobinamide as a mixture of the two isomers which differ in the relative orientation of the axial ligands. This leads to the first reported value for an equilibrium constant (axial ligands only given) involving the substitution of co-ordinated H2O by HC2- of K = [HC2-Co-OH2]/([H2O-Co-OH2] [HC2-]) ≥ 1023 dm3 mol-1. Equilibrium constants have been determined for the substitution of co-ordinated H2O in ethynylaquocobinamide by OH- (pK = 13.0 ± 0.1), CN- (log10K ≥ 6.8), and imidazole (log10K = 3.4), which confirm the position of HC2- between cyanide and vinyl in the trans-effect series for CoIII corrinoids.

Original languageEnglish (US)
Pages (from-to)225-229
Number of pages5
JournalJournal of the Chemical Society, Dalton Transactions
Issue number2
DOIs
StatePublished - Jan 1 1983
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)

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