Molecular structures and hydrogen bonding in the crystalline hydrates of two flexible double betaines with different quaternary ammonio groups in the adipic acid skeleton

Abstract

Crystalline dihydrates of two flexible double betaines −O 2CCH(R)CH 2CH 2CH(R)CO − 2 ( 1, R = Me 3N +, 2, R = C 5H 5N +) have been characterized by single-crystal X-ray analysis. Both compounds crystallize in the monoclinic space group P2 1 c with a = 7.463(4), b = 10.312(6), c = 9.978(5) A ̊ , β = 90.18(5)°, Z = 2 for 1·2H 2O and a = 9.063(2), b = 7.665(1), c = 11.962(1) A ̊ , β = 94.89(1)°, Z = 2 for 2·2H 2O. Both betaine molecules occupy l̄ sites but differ with regard to the orientation of the carboxylate groups and ammonio groups. In each crystal structure, the formation of donor hydrogen bonds from the water molecules to adjacent carboxylate groups gives rise to an infinte two-dimensional network composed of a packing of identical 26-membered rings.