Conformational polymorphism in N-(4'-methoxyphenyl)- 3-bromothiobenzamide.

Three conformational polymorphs of N-(4'-methoxyphenyl)-3-bromothiobenzamide, yellow alpha, orange beta, and yellow gamma, have been identified by single-crystal X-ray diffraction. The properties and structure of the polymorphs were examined with FT Raman, FTIR (ATR), and UV/Vis spectroscopy, as well as differential scanning calorimetry. Computational data on rotational barriers in the isolated gas-phase molecule indicate that the molecular conformation found in the alpha form is energetically preferred, but only by around 2 kJ mol(-1) over the gamma conformation.