THE (1/1) ADDUCTS OF (2,4-DICHLOROPHENOXY)ACETIC ACID WITH 4-AMINOBENZOIC ACID AND TRIPHENYLPHOSPHINE OXIDE

The (1:1) molecular adducts between the herbicide (2,4-dichlorophenoxy)acetic acid (2,4-D) and 4-aminobenzoic acid, [(2,4-D)(4-ABA)], (1) and triphenylphosphine oxide, [(2,4-D)(TPPO)], (2) have been determined by X-ray diffraction and refined to residuals R = 0.077 and 0.054 for 1 588 and 5051 observed reflections respectively. With adduct (1), the planar molecules of 2,4-D and 4-ABA form into hydrogen bonded tetramer units via the carboxylic acid groups of 2,4-D and the amino groups of 4-ABA (O---N, 2.74, 2.75 angstrom). These units then hydrogen bond, giving molecular stacks (O---N, 2.81 angstrom). In contrast, the two independent molecules of 2,4-D in the asymmetric unit of (2) are antiplanar and are hydrogen bonded to the TPPO molecules [2.58, 2.61 angstrom]. The two independent TPPO molecules are also conformationally dissimilar.