ABSTRACT
A comparative structural analysis of the two polymorphic forms of (1R,3S)-3-(p-thioanisoyl)-1,2,2-trimethylcyclopentanecarboxylic acid has been performed with infrared, Raman, and 13C NMR spectroscopy. The results are compared with those of the crystallographic and thermal studies on the two forms published in previous papers. The enantiotropism of the polymorphs as well as the differences in the conformation of the carboxyl group and the resulting intermolecular hydrogen bonds were confirmed by the infrared and Raman studies.
Subject(s)
Benzoates/chemistry , Cyclopentanes/chemistry , Calorimetry, Differential Scanning , Carbon Isotopes , Chemical Phenomena , Chemistry, Physical , Crystallization , Magnetic Resonance Spectroscopy/methods , Solutions , Spectrophotometry, Infrared , Spectrum Analysis, RamanABSTRACT
The crystal structure of polymorph I of p-(1R,3S)3-thioanisoyl-1,2,2-trimethylcyclopentane carboxylic acid has been determined and is compared with that of polymorph II that was previously described. Polymorph I is very different at the level of the carboxyl group. It does not present disorder and the values found for the C-O bonds correspond exactly to single and double bond lengths. In addition, the carboxyl groups of the two molecules in the cell packing are involved in symmetric hydrogen bonds [2.662(6) A] leading to the formation of a dimer around the twofold axis following x with a shift on z. The different conformations on the carboxylic group between the two polymorphs are in good agreement with the thermodynamic study.
