Interactions of morphine and codeine with benzoic acid and substituted benzoic acids

Interactions of morphine and codeine with benzoic acid and substituted benzoic acids in methanol have been investigated spectrophotometrically. Morphine and codeine form fairly stable and similar complexes with the ligands. The complexes formed are assumed to be due to Van der Waals type of co-operative effects of different forces together with the possibility of H-bonding. The aromatic compounds are accommodated to the flat surface or cavity part of piperidine ring of morphine and codeine.