Crystal structure of isopropyl 2-hy-droxy-2-phenyl-acetate: a pharmacopoeia reference standard.

The title compound, CHO, is used as a pharmacopoeia reference standard for determining impurities in the drug Pregabalin, used for the treatment of epilepsy and diabetic neuropathic pain. The mol-ecule is far from being planar, with the dihedral angle between the planes of the aromatic ring and the carboxyl fragment (O-C=O) being 76.1 (6)°. The isopropyl substituent is located in a synperiplanar position relative to the C=O bond and is turned so that the C-O-C-H torsion angle is -43.7°. In the crystal, bifurcated O-H⋯(O,O) hydrogen bonds, enclosing (5) ring motifs, lead to the formation of chains propagating along the -axis direction. Inversion-related chains are linked by the C-H⋯O hydrogen bonds, forming undulating layers lying parallel to the plane.