The tautomer ratio of histamine
- 1 October 1973
- journal article
- Published by Oxford University Press (OUP) in Journal of Pharmacy and Pharmacology
- Vol. 25 (10) , 787-792
- https://doi.org/10.1111/j.2042-7158.1973.tb09942.x
Abstract
The tautomeric equilibrium constant Kt for the two tautomeric forms (Nτ-H and Nπ-H) of histamine mono-cation is determined from the difference between the pKa values of Nπ- and Nτ-methylhistamines, and of Nπ- and Nτ-benzylhistamines. The ratio of concentrations of tautomers [Nτ-H]/[Nπ-H] = Kt is 4ṁ2 indicating that the histamine mono-cation exists in aqueous solution approximately 80% as the Nτ-H-tautomer and 20% as the Nπ-H tautomer. From the value of Kt and pKa1 of histamine the individual ionization constants at 25° of the two tautomers are derived. Tautomer Nτ-H (pKa1 6ṁ16) is a slightly weaker base than is tautomer Nπ-H (pKa1 6ṁ79).Keywords
This publication has 14 references indexed in Scilit:
- Determination of the tautomeric form of the imidazole ring of L-histidine in basic solution by carbon-13 magnetic resonance spectroscopyJournal of the American Chemical Society, 1973
- Ionization of histamine, N-acetylhistamine, and their iodinated derivativesJournal of Medicinal Chemistry, 1970
- Molecular orbital calculations of the preferred conformations of histamine and a theory on its dual activityJournal of Medicinal Chemistry, 1968
- RECEPTORS MEDIATING SOME ACTIONS OF HISTAMINEBritish Journal of Pharmacology and Chemotherapy, 1966
- Prototropic Tautomerism of Heteroaromatic Compounds: I. General Discussion and Methods of StudyPublished by Elsevier ,1963
- Copper(II) Complexes of Histamine and 3-Methyl HistamineNature, 1960
- 271. The mechanisms of N-substitution in glyoxaline derivatives. Part I. Introduction, and study of prototropic equilibria involving 4(5)-nitroglyoxalineJournal of the Chemical Society, 1960
- Studies on Imidazoles. III. 1-Substituted Analogs of Histidine and HistamineJournal of the American Chemical Society, 1949
- The Relation between Structure and Histamine-Like ActivityJournal of the American Chemical Society, 1942
- CCXLV.—AminoalkylglyoxalinesJournal of the Chemical Society, Transactions, 1911