Thermodynamic considerations in co-ordination. Part IV. Calorimetric studies on histamine [4(5)-(2-aminoethyl)imidazole] and isohistamine [2-(2-aminoethyl)imidazole]

Abstract

Enthalpy and entropy data have been obtained for the protonation of isohistamine and for the formation of its copper complex. The calorimetric data for the copper complex were obtained at a pH low enough to avoid the formation of hydrolysis products. Data for the copper–histamine system have been redetermined in conditions which avoid hydrolysis. The construction of a precision incremental titration calorimeter is described.