An X-ray study of the p-n-alkoxybenzoic acids. Part III. Crystal structure of p-ethoxybenzoic acid

Abstract

The crystal structure of the title compound has been determined from 740 reflections measured by diffractometer. Crystals are monoclinic, a= 27.148(4), b= 4.013(1), c= 21.787(3)Å, β= 135.97(1)°, space group C2/c, Z= 8. The structure was solved by a fit of the weighted reciprocal lattice to the calculated Fourier transform for the molecule, and refined by block-diagonal least-squares to R 0.053.

The carboxy-group seems to be disordered by 180° rotation about the C–C bond joining it to the phenyl ring. The structure, including small deviations from overall planarity, is similar to that of p-methoxybenzoic acid. Molecules exist as centrosymmetric hydrogen-bonded dimers [O ⋯ O 2.600(3)Å] the packing being similar to that of anisic acid, but significantly different from that of higher homologues.