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

Abstract

The crystal structure of the title compound has been determined from 1951 diffractometer data. Crystals are triclinic, a= 7.744(1), b= 10.676(2), c= 14.278(2)Å, α= 95.54(2), β= 108.42(1), γ= 102.63(1)°, space group P, Z= 4. The structure was solved by Patterson methods, and refined by least-squares methods to R0.050.

The molecules form hydrogen-bonded dimers (O–H ⋯ O 2.600 and 2.652(3)Å), but different conformations are found for the two crystallographically independent molecules in the asymmetric unit. Both butyl groups adopt extended near-planar arrangements with the O–C (α)–C(β)–C(γ) side-chain torsion angles 176 and 64°. The carboxy-groups are not coplanar with the phenyl rings, and one is disordered by 180° rotation about the C–C bond linking it to the ring, leading to equivalent C–O bond lengths. The reason that this compound shows liquid-crystalline behaviour, unlike its methoxy- and ethoxy-homologues, is given in terms of molecular packing.