X-ray crystallographic determination of the structure and conformation of trans-2-tribromomethyl-5-trichloromethyl-1,3-dioxolan-4-one: an analogue of chloralide

trans-2-Tribromomethyl-5-trichloromethyl-1,3-dioxolan-4-one is monoclinic,P2₁/c,a=6.381(6),b=17.116(6),c=10.598(5) Å,=94.07(6)°,Z=4. The structure was solved by direct methods from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by full-matrix least squares to a finalR value of 0.042 using 1274 reflections. The conformation of the molecule is very similar to that of chloralide with the 5-mem-bered ring being almost planar. Evidence is provided for a possible C-HO intermolecular interaction. The average C-Br distance is 1.931(11) Å and the average Br-C-Br angle is 109.7(9)°. A table of average C-Br bond lengths and Br-C-Br angles, with the ranges for these parameters, in compounds containing -CBr₃ groups is given. Some¹H NMR and mass spectra data are included for the title compound and for chloralide.