The apparent p Ka of the oxidation product of spermine or spermidine: A p Ka masked by a ring-chain tautomeric equilibrium

Abstract

The previously reported acid titration curve (S. Brandänge, L.-H. Eriksson, and B. Rodriguez, Acta Chem. Scand., 1984, B38, 526) for the aminal oxidation product of the title compounds in D 2O is computer simulated based on a model consisting of a ring-chain tautomeric equilibrium ( K T) for the monodeuteronated bicyclic aminal followed by a second deuteronation of the resultant monocyclic primary amine ( K a1 ) to give a dication. The fractional amount of dicationic acid product is given by the term [D +] ([D +] + K app ) where K app, the apparent dissociation constant, equals 5.47 × 10 −6, the product of K T and K a1 .