Microwave Spectrum, Structure, and Quadrupole Coupling Constant Tensor of Ethyl Bromide

Publisher Website
Google Scholar
Abstract
The microwave spectra of 10 isotopic species of ethyl bromide have been measured and assigned, viz., the 79Br and 81Br species of CH3CH2Br, CH3CD2Br, CD3CH2Br, CH313CH2Br, and 13CH3CH2Br. The spectra reported lie in the region of 18 to 31 kMc. The complete structure has been determined by the substitution method, giving the following bond parameters: CC = 1.518 Å, CBr = 1.950 Å, CCBr = 111°2′, CH (methylene) = 1.087 Å, HCH (methylene) = 109°54′, CCH (methylene) = 112°15′, HCBr = 105°25′, CH (methyl) = 1.093 Å, and HCH (methyl) = 108°52′. The principal quadrupole coupling parameters have been determined to be χzz = 541 Mc, χxx = —267 Mc, and χyy = —274 Mc for C2H579Br and χzz = 450 Mc, χxx = —220 Mc, and χyy = —230 Mc for C2H581Br. Through the analysis of second‐order effects of quadrupole coupling on hyperfine structure, it was determined that, within experimental error, the CBr internuclear line and the ``z'' principal quadrupole axis coincide, indicating that the CBr bond is not bent. The barrier to internal rotation, recalculated using Lide's splitting measurements, and the above structure is 3684 cal/mole.