Equilibrium molecular structure of orotic acid from gas-phase electron diffraction data and quantum-chemical calculations

The accurate equilibrium structures of planar anti and syn orotic acid conformers with different positions of the carboxyl group with respect to the C=C bond were determined from gas-phase electron diffraction data using the dynamic model and taking into account anharmonic vibrational corrections calculated with ab initio force field. The high accuracy of coupled-cluster computations was exploited in the analysis of structural effects due to electron-acceptor substituents.