Tautomeric and conformational properties of dibenzoylmethane, C6H5–C(O)–CH2–C(O)–C6H5: gas-phase electron diffraction and quantum chemical study

Abstract

Tautomeric and structural properties of dibenzoylmethane, C6H5–C(O)–CH2–C(O)–C6H5, have been investigated by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximation with different basis sets up to cc-pVTZ). Analysis of GED intensities resulted in the presence of 100(5)% enol tautomer at 380(5) K. The enol ring possesses C S symmetry with a strongly asymmetric hydrogen bond. The two phenyl rings are rotated with respect to the enol ring by 15.1(5.0) and 12.1(5.8)°. The experimental geometric parameters are reproduced very closely by the B3LYP/cc-pVTZ method.