The structure and torsional properties of oxalyl chloride fluoride in the gas phase have been measured by electron diffraction at temperatures of 22, 81, 158, and 310 degrees C. The molecule may be regarded as a hybrid of oxalyl chloride and oxalyl fluoride. Since the former exists as a more stable periplanar anti form (phi = 180 degrees) in equilibrium with a less stable gauche form (phi 600) and the latter as an equilibrium between two periplanar forms, anti and syn, the second form of oxalyl chloride fluoride is an interesting question. It was found to be gauche. The system was modeled as two rotational conformers related by a potential of the form 2V= V(1)(1 + cos phi) - V(2)(1 - cos 2 phi) + V(3)(1 + cos 3 phi). The anti/gauche bond distances and bond angles (r(g)/Angstroms, angle(alpha)/degrees) with estimated 2 sigma uncertainties at 22 degrees C are (r(C=O)) = 1.183(2)11.182(2), Delta r(C=0) = 0.003(6)/0.002(6) (assumed from theory), r(C F) = 1.329(3)/1.335(3), r(C-Cl) = 1.738(2)/1.753(2), angle(C-C-Cl) = 112.0(3)/111.9(3), angle(C-C=O3) = 123.0(4)/123.2(4), angle(O=C-Cl) = 125.0(2)/ 1.249(2), angle(O=C F) = 123.0(3)1125.1(3), and angle(Cl-C-C-F) = 180.0/59.8. The variation of composition with temperature afforded a determination of the standard enthalpy and entropy of the reaction anti gauche. The results are Delta H degrees = 2.5(12) kcal/mol and Delta S degrees = 6.5(33) cal/(mol.K). The structures and equilibria are discussed.