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Updated: Aug 18, 2026

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
Published on: September 26, 2016
Hydrogen-bonded trimers in 4,4'-dimethylbiphenyl-2,2'-dicarboxylic acid
1Department of Chemistry, Ohio State University, Columbus 43210, USA. gerkin@chemistry.ohio-state.edu
Abstract:
The title acid, C16H14O4, crystallized in the centrosymmetric space group C2/c with 1.5 molecules in the asymmetric unit. Each of the three independent carboxylic H atoms is ordered, and each participates in hydrogen bonding. The OD...OA distances in the hydrogen bonds are 2.584 (2), 2.647 (2) and 2.722 (2) A. Three sets of cyclic dimer hydrogen bonds are formed within and between two asymmetric units, linking them into molecular trimers. The trimers lie on twofold axes which bisect the central C-C bond of one molecule and the COOH dimer connecting the other two. The two biphenyl twist angles are 68.1 (1) and 64.6 (1) degrees. The dihedral angles between the benzene-ring planes and the planes of the carboxyl groups attached to them are 0.7 (3), 23.3 (2) and 18.4 (2) degrees. Structural comparisons are made with the 'parent' compound, diphenic acid, and with the isomeric compound, 6,6'-dimethylbiphenyl-2,2'-dicarboxylic acid.
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