Microdetermination of aliphatic diamines and polyamines with cupric ion

Abstract

The reactions of diamines and polyamines with cupric ion were investigated potentiometrically, using a copper ion-selective indicator electrode and a single-junction reference electrode. In general, cupric ion reacted with 2 mol of vic-diamines or their salts. Tetraaza compounds reacted on an equimolar basis with Cu(II). Both vic-diamines and their salts, as well as tetraaza compounds, could be titrated in the presence of excess ammonia. With cupric ion in ammoniacal solution these compounds yield a characteristic purple/violet color. Diamines separated by more than two methylene groups cannot be determined in the presence of ammonia and yield a blue color. Diamines with more than four methylene groups react with cupric ion on an equimolar basis, also yielding a blue color.