AB-INITIO STUDY OF CONFORMATIONS AND VIBR ATIONAL FREQUENCIES OF SQUARIC ACID

Ab initio SCF calculations of conformations of squaric acid have been reported. The ZZ isomer is found to be the most stable in the three pl anar isomers. An isodesmic energy analysis has been carried out at the HF 6-31G*//6-31G** level for the three planar isomers. The three iso mers have positive isodesmic energies or small negtive ones, suggestin g that squaric acid is not aromatic. Vibrational frequencies have been calculated for the three isomers.