Vibrational Spectra and Structure of Oxalyl Fluoride in the Solid and Fluid States

Abstract

The vibrational spectra of oxalyl fluoride have been examined in the solid phase and re-examined in the fluid phases. From the disappearance of three major bands upon solidification, it is concluded that there must be two isomeric forms in the vapor. The spectra have been assigned on the basis of two isomers; solid-phase frequencies were used for the trans fundamentals and bands unique to the fluid states were assigned to the cis isomer. The values observed for the fundamentals in the solid are compared to those previously reported from studies of the fluid states. The internal torsion was observed at 54 cm−1 in the vapor state, and a barrier to internal rotation of 12.4 kcal/mole has been calculated. A comparison of the infrared and Raman bands in the crystal shows that the mutual exclusion principle is operative. It is concluded from this alternate forbiddance that the molecule has a centrosymmetric structure in the crystal and that each molecule occupies a Ci site. The factor group of the crystal is believed to be either C2h or D2h with two or four molecules per primitive cell.