Methyl(phenyl)phosphinic acid

The crystal structure of the title compound, C7H9O2P, displays O—H⋯O hydrogen bonding , which links individual molecules related via the c-glide plane and translational symmetry along the crystallographic b-axis direction into continuous chains.

The crystal structure of the title compound, C 7 H 9 O 2 P, displays O-HÁ Á ÁO hydrogen bonding , which links individual molecules related via the c-glide plane and translational symmetry along the crystallographic b-axis direction into continuous chains.
The title compound, Fig. 1, crystallizes as a racemic mixture of enantiomers in the centrosymmetric space group Pbca.
An analysis of the geometry of (I) by Mogul [Bruno et al., 2004] using the Cambridge Structural Database [CSD, Allen, 2002] shows no unusual features; all absolute values of the z scores were below 1.0. An enhanced figure is provided, Fig. 2.
The crystal structure of (I) shows hydrogen bonding between the phosphinic acid moieties of the type OH···O=P-OH···O=P related by the c glide plane and translational symmetry along the crystallographic b direction to form continuous chains, Table 1. The very short P-O···O=P distance of 2.494 (2) Å indicates a strong hydrogen bond. This is very slightly shorter than the average O···O interaction distance in the CSD of 2.51 (5) Å for 45 observations for other phosphinic acids.
The packing diagram, Fig. 3, shows that the hydrogen bonded chains of (I) pack together in a head-to-head fashion in the crystallographic b direction to form columns. Neighboring columns in the crystallographic a direction run in the opposite direction with the neighboring methyl groups packing together. The effect creates a pseudo-lamellar structure parallel to the crystallographic ab plane where the phosphinate groups and methyl groups are in a plane surrounded by phenyl groups on either side. There are no phenyl-phenyl interactions. The distance between layers is half the c axis distance, 7.9900 (5) Å.

Refinement
The H atom on O1 was found in the difference Fourier map and its position was allowed to refine freely while its isotropic displacement parameter was set to 1.5 times U eq of O1. H atoms were positioned geometrically and allowed to ride on supplementary materials sup-2 their parent atoms with C-H bond lengths of 0.93 Å (aromatic CH) and 0.96 Å (methyl CH 3 ) and isotropic displacement parameters equal to 1.2 times U eq of the parent atom. Fig. 1. The molecular structure of (I) showing the atomic labelling scheme. The anisotropic displacement parameters are at the 30% level; H atoms are represented by circles of arbitrary size. Fig. 2. The packing diagram of (I) looking down the crystallographic a direction with the crystallographic b axis up. The H bonding are shown as red dashed lines and phenyl (C 6 H 5 ) groups shown as sticks for clarity. Geometric parameters (Å, °)