Acid-Base Relationships and Tautomeric Equilibria in m-Aminobenzoic Acid, 3-Amino-1-naphthoic Acid, and 4-Amino-2-naphthoic Acid

Abstract

The first and second ionization constants have been determined in aqueous solution of m-aminobenzoic acid, 3-amino-1-naphthoic acid, and 4-amino-2-naphthoic acid. From published values of the ionization constants for the methyl esters, the ionization constants have been evaluated for the four equilibria involved in each case and estimates have been made of the effects of the substituents NH₃⁺ and NH₂ on the ionization of the COOH, and of the substituents COOH and COO^- on the ionization of the NH₃⁺ group. These values and the tautomeric constants are interpreted in terms of structure and are discussed in relation to previous studies on substitution in the naphthalene ring.