COMPARATIVE-STUDY OF THE 2 POLYMORPHIC FORMS OF P(1R,3S) 3-THIOANISOYL-1,2,2-TRIMETHYLCYCLOPENTANE CARBOXYLIC-ACID

The crystal structure of polymorph I of p(1R,3S)3-thioanisoyl-1,2,2-tr imethylcyclopentane carboxylic acid has been determined and is compare d with that of polymorph II that was previously described. Polymorph I is very different at the level of the carboxyl group. It does not pre sent disorder and the values found for the C-O bonds correspond exactl y to single and double bond lengths. In addition, the carboxyl groups of the two molecules in the cell packing are involved in symmetric hyd rogen bonds [2.662(6) Angstrom] leading to the formation of a dimer ar ound the twofold axis following x with a shift on z. The different con formations on the carboxylic group between the two polymorphs are in g ood agreement with the thermodynamic study.