Abstract

In order for a substituted benzoate ion to combine most effectively with the receptor site of antibody to the p-azobenzoate group, it appears that the carboxylate group must be coplanar with the benzene ring. o-Aminobenzoate and monosubstituted o-aminobenzoates are accommodated, while disubstituted o-aminobenzoates are not. The ability of the former compounds to form an intramolecular hydrogen bond between the hydrogen of the amino group and the carboxylate preserves the planar structure which appears to be necessary for effective combination with antibody. Thus the observation that ortho substituents in general interfere with the combination stems from the fact that they tilt the carboxylate out of the plane of the benzene ring.