STRUCTURE OF A 1 1 COMPLEX BETWEEN THE ANTHELMINTIC DRUG MEBENDAZOLE AND PROPIONIC-ACID/

Recrystallization of the anthelmintic drug mebendazole from propionic acid yields a 1:1 molecular complex which crystallizes in the triclini c system space group P (1) over bar, a 5.928(2), b = 11.066(2), c = 14 .337(6)Angstrom, alpha = 94.89(3), beta = 101.56(3), gamma = 96.18(2)d egrees, and Z = 2 complex units in the unit cell. An x-ray diffraction study revealed an R-2(2)(8) hydrogen bonding system in the complex, i nvolving the unprotonated imidazole N and amide N-H function of the dr ug and the acid carboxylic group. Complex molecules form centrosymmetr ic dimers by intermolecular N-H ... O hydrogen bonding involving the p rotonated imidazole N atom and the benzoyl O atom of the drug molecule .