Author:
Císařová Ivana,Podlaha Jaroslav,Böhm Stanislav,Exner Otto
Abstract
Structure of 2,3-dimethylbenzoic acid was determined both by single-crystal X-ray diffraction and by ab initio calculation at an RHF/6-31+G** level. Comparing with a previous X-ray analysis of another crystal modification of the same compound, it was possible to estimate the effect of crystal forces on the conformation. The isolated molecule is not planar as deduced previously, mainly from IR spectra, but the carboxyl group is twisted out of the ring plane by a torsion angle ϕ = 12°. In the crystal, the molecule is more flat and ϕ is reduced to 7 and 1° in the two modifications, respectively. Further significant differences between the modifications were not detected. The flattening in the crystal structure is accompanied by additional small changes in the geometry, connected with greater steric crowding in the less twisted molecule: the example shows well the limits in which molecular structure can be deduced from the solid-state structure. Previous division of methylated benzoic acids into two subgroups, planar and nonplanar, is to be formulated with more precision: the former group includes even acids with nearly planar conformation (ϕ up to 15°).
Publisher
Institute of Organic Chemistry & Biochemistry
Cited by
10 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献