Gas phase electron diffraction study of the molecular structure of 6,6′-dinitro-2,2′-diphenic acid

Abstract

The 6,6′-dinitro-2,2′-diphenic acid molecule has been studied by gas phase electron diffraction. The structure analysis (based on C i symmetry for the molecule as a whole and D 6h, C 2v and C s symmetries for the phenyl rings, the nitro and carboxyl groups, respectively) gives the following parameters (bond lengths, r a, in Å; angles in degrees): ▪; CC ⪕ = 1.505 (14); CO = 1.212(8); CO = 1.409(21); CCO = 126.6(1.6); CCO = 111.8(1.3); the angle between the planes of the two phenyl rings, 71.2(0.7); the torsional angle of nitro groups, 30.4(1.4); the torsional angle of carboxyl groups, 25.1(1.5). The uncertainties given in parentheses represent three times the standard deviation values. The results are compared with the structural data on biphenyl derivatives, monomers and dimers of organic acids. The observed distances between the oxygen atoms of nitro groups and the oxygen atoms of hydroxyl groups are 2.693(26) Å which may offer strong support for intramolecular hydrogen bonding.