Microwave Spectrum of Ethyl Bromide

Abstract

The microwave spectrum of ethyl bromide has been investigated and accurate values for the rotational constants B and C and the asymmetry parameter b have been obtained. For C₂H₅Br⁷⁹ B=3804.5 Mc, C=3522.5 Mc, b= —0.00487949 and for C₂H₅Br⁸¹ B=3781.5 Mc, C=3503.0 Mc, and b= —0.00522977. The following model reproduces these constants to within 2 Mc: C–C 1.5495 A, C–H 1.110 A, C–Br 1.9400 A ≰ C –C–H 110°00′, ≰C–C–Br 110°30′. Analysis of the quadrupole hyperfine structure indicates that eqQ along the C–Br bond axis is 537.5 Mc for C₂H₅Br⁷⁹ and 450.9 Mc for C₂H₅Br⁸¹. Two transitions have not been able to be fitted by first‐order or second‐order nondegenerate quadrupole theory. The torsional frequency is estimated to be 202 cm^—1 and the barrier height is 2.80 kcal/mole.