Conformational comparisons between phenoxyacetic acid derivatives in adducts and those in the free form. Part 2

Abstract

Nine molecular co-crystals containing 2,3-, 2,5-, 2,6- and (3,5-dichlorophenoxy)acetic acid have been prepared and studied using single-crystal X-ray diffraction techniques. The free acid structure of (2,3-dichlorophenoxy)acetic acid is also reported. The bases used to prepare the adducts were 2-aminopyrimidine, 2-amino-2-thiazoline, 2-amino-5-chlorobenzoxazole and 4,4’-dipyridine. The conformations of the phenoxyacetic acid molecules were found in all but one case to be either synclinal (twisted) or antiperiplanar (planar). The one exception was a molecule of (2,6-dichlorophenoxy)acetic acid whose conformation was assigned as anticlinal. General comments are given about the conformational aspects of these and previously reported adducts of phenoxyacetic acid derivatives and how they compare to their free acid structures.