Characterization of the species-specific acid-base equilibria of adrenaline and noradrenaline

Abstract

Adrenaline, noradrenaline, the biogenic catecholamines of vital importance, and four closely related compounds were studied by ¹H NMR-pH titrations, and the resulting acid-base properties are quantified in terms of three macroscopic and twelve microscopic protonation constants for both molecules. The species-specific basicities are interpreted by means of inductive and shielding effects by comparing the protonation constants of the catecholamines, including dopamine. The site-specific basicities determined this way could be key parameters for the interpretation of biochemical behavior.

Keywords: Catecholamine; Epinephrine; Microspeciation; NMR-pH titration; pK(a).