THEORETICAL CONFORMATIONAL-ANALYSIS OF SUBSTITUTED PHENYLBENZOATES

Conformation analysis of phenylbenzoate, a characteristic moiety of several liquid crystal compounds, was done using the NDDO semiempirical molecular oribital method. Calculated and experimental torsional angles (the latter found in various model molecules) agree nicely. The most probable conformation of DB-PBB (4-butylphenyl-4 prime -butylbenzoyloxy benzoate), existing in the solid phase and probably also in the mesophase, is an extended one. The C3-C4-C7-O8-torsional angle is synclinal while C4-C7-O9-C10 is periplanar. Calculations indicate that substituted phenyl-4-benzoyloxybenzoates are rather flexible molecules. Rotation by an angle less than 20 degree around any of the C4C7, C7O9 and O9C10 bonds needs at most 10 kJ/mol energy.