F. Takusagawa, K. Hirotsu, A. Shimada
May 1, 1971
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0
Influential Citations
41
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Journal
Bulletin of the Chemical Society of Japan
Abstract
The crystal structure of pyromellitic acid dihydrate has been determined by the method of X-ray diffraction. The crystal is triclinic in the P\bar1 space group, with Z=1 and cell dimensions of a=10.05, b=6.45, c=5.45 A, α=74.5°, β=112.2°, and γ=77.3°. The structure was derived from the three-dimensional Patterson function and was later refined by the least-squares method, using the anisotropic thermal parameters, to give a final R index of 7.4%. All the hydrogen atoms were located on the difference-synthesis map. The average C(ring)–C(ring) distance is 1.386 A, while the average C(ring)–C(carboxyl) distance is 1.496 A. One carboxyl group is twisted by 17.9°, and the other is twisted by 74.5°, out of the plane of the benzene ring. The C–O(H) and C=O distances differ significantly from each other, the average values being 1.302 and 1.211 A respectively. Four types of hydrogen bonds, with an average O–H···O distance of 2.732 A, form a three-dimensional network. Thus, each molecule is joined, through hydrogen...