Vibrational Spectrum of Tetrabromoethylene

Abstract

The infrared spectrum of C₂Br₄ in various solvents and as a liquid has been observed and measured in the range 3—100μ. The new data, in conjunction with earlier results and force constant calculations, have enabled for the first time an essentially complete and satisfactory vibrational assignment. The fundamentals, in units of cm^—1, are 1535, 265, 144 in a_1g; 880, 208 in b_1g; 766, 119 in b_2u; 635, 188 in b_3u; 66 in a_1u; 245 in b_1u; and 464 in b_2g. The present results for C₂Br₄ have required that two changes be made in the earlier assignment for C₂Cl₄. The angular modes of the chloro compound in b_1u and b_3u are now found to be at 288 and 310 cm^—1, respectively. The assignments for C₂F₄, C₂Cl₄, and C₂Br₄ are then complete and concordant.