Molecular Cocrystals of Carboxylic Acids. XVII. Spectral Characterization of the Adducts of Triphenylphosphine Oxide With Substituted Phenoxyacetic Acids and the Crystal Structure of the 1 : 1 Adduct With (4-Chloro-2-methylphenoxy)acetic Acid

Abstract

A series of 1:1 molecular adducts of triphenylphosphine oxide ( tppo ) with substituted phenoxyacetic acids has been prepared and characterized by using infrared, solid-state ¹H and ³¹P n.m.r. spectroscopy, and X-ray powder diffraction methods. The crystal structure of one of these, with the herbicidally active (4-chloro-2-methylphenoxy)acetic acid ( mcpa ),[( tppo )( mcpa )], has been determined by X-ray diffraction methods. This compound is isomorphous with the tppo adduct of (2,4-dichlorophenoxy)acetic acid. The title compound has two independent and different molecular adducts in the asymmetric unit each with strong hydrogen-bonding interactions between the carboxylic acid proton and the phosphoryl oxygen of tppo [O...O, 2.579, 2.647(9)Ǻ].