Microwave Spectrum of Ethyl Bromide

Abstract

The microwave spectrum of ethyl bromide has been investigated and accurate values for the rotational constants Band C and the asymmetry parameter b have been obtained. For C2H.Br 79 B=3804.5 Mc, C=3522.5 Mc, b= -0.00487949 and for C2H.Br 81 B=3781.5 Mc, C=3503.0 Me, 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 1:C-C-H 110°00', 1: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 C2H,Br 79 and 450.9 Mc for C2H.Br 81 • Two transitionshave 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.

Theoretical Studies on the Thermochemistry of Stable Closed-Shell C1 and C2 Brominated Hydrocarbons

“…The G3X barrier heights for torsion motion in C 2 H 5 Br, CH 3 CHBr 2 , CH 3 CBr 3 , CH 2 BrCBr 3 , C 2 HBr 5 , and C 2 Br 6 are 14.7, 17.8, 23.2, 37.1, 53.7, and 86.3 kJ/mol, respectively. The values agree with the available spectroscopic analysis for C 2 H 5 Br of 11.7, 14.9, and 15.4, for CH 3 CHBr 2 of 17.8, and for CH 3 CBr 3 of 23.0 kJ/mol, etc. The estimated barrier height of 83.0 kJ/mol for C 2 Br 6 by Kudchadker and Kudchaker is also supported by our G3X calculations.…”

Thermodynamic Functions for n-Halogenated Hydrocarbons

“…* Raman, liquid (3). * Wagner, Dailey, and Solimene [microwave (35)] suggest that this CH3 torsion be 202 cm.-1 ' McDewitt (21) specifies that this C-Br stretching be 560cm.-1 and C-I stretchingbe 497 cm.-1, respectively. * Following Green and Holden (12) we introduce all equal high frequency assignments.…”