Biphenyl-3-carboxylic acid at 296 and 203 K.

In biphenyl-3-carboxylic acid, C13H10O2, hydrogen bonding is of the cyclic-dimer type about a center of symmetry. The carboxyl H atom is ordered. The dihedral angle between the planar phenyl rings is 31.78(8) degrees at 296 K and 31.27(6) degrees at 203 K. The data show that the larger-than-average magnitudes of the displacement parameters of the carboxylic O atoms are due to thermal motion rather than static disorder.