The chemistry of vitamin B12. Part 20. Diaquocobinamide: pK values and evidence for conformational isomers

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

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

An improved method for preparing aqueous solutions of diaquocobinamide without hydrolysis products is described. The pKa values have been determined in 0.2 mol dm-3 NaClO4 at 25 °C as pK1 = 5.9 ± 0.1 and pK2 = 10.3 ± 0.2 and are shown to involve one proton each. Evidence is presented that diaquo-, aquohydroxo-, and dihydroxo-cobinamide exist in solution as isomers depending on hydrogen bonding between the axial ligands and different amide side-chains.

Original languageEnglish (US)
Pages (from-to)217-223
Number of pages7
JournalJournal of the Chemical Society, Dalton Transactions
Issue number2
DOIs
StatePublished - 1983
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)

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