Ab initioSTO-3G optimization of planar,perpendicular, and twisted molecular structures of biphenyl

The complete molecular structure of biphenyl, characterized by 12 independent parameters, has been derived by ab initio gradient techniques using a STO -3G basis set for coplanar, perpendicular, and minimum energy conformations with the constraint of planar phenyl ring units and a C₂ symmetry axis along the CC interring bond. The minimum torsional angle obtained was ? = 38.63° with torsional energy barriers of 8.59 and 10.04 kJ/mol for ? = 0° and ? = 90°, respectively.