Microwave Spectrum, Structure, and Nuclear Quadrupole Coupling Constants of 1-Bromo-1-fluoroethane

✍ Scribed by Yoshio Tatamitani; Susumu Kuwano; Kiyokatu Fuchigami; Sumio Oe; Teruhiko Ogata

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 265 KB
• Volume: 196
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1999.7863

✦ Synopsis

The microwave spectrum of 1-bromo-1-fluoroethane, CHBrF-CH 3 and CHBrF-CH 2 D ( 79/81 Br), has been studied for the first time from 8 to 41 GHz. A least-squares analysis of the observed a-and b-type transition frequencies gave rotational and centrifugal distortion constants and components of the bromine nuclear quadrupole coupling constant tensor in the principal axes system as follows:

75(4) kHz, aa ϭ 493.49(29) MHz, bb Ϫ cc ϭ Ϫ38.89(11) MHz, and ͉ ab ͉ ϭ 161.8(28) MHz for the CH 79 BrF-CH 3 species; A ϭ 8979.257(5) MHz, B ϭ 2859.072(3) MHz, C ϭ 2294.572(3), ⌬ J ϭ 0.76(2) kHz, ⌬ JK ϭ 2.51(3) kHz, ⌬ K ϭ 4.5(4) kHz, ␦ J ϭ 0.145(1) kHz, ␦ K ϭ 2.70(4) kHz, aa ϭ 412.42(27) MHz, bb Ϫ cc ϭ Ϫ32.56 (11) MHz, and ͉ ab ͉ ϭ 133.3(3) MHz for the CH 81 BrF-CH 3 species.

The structural parameters are calculated from the 24 observed rotational constants, and electronic properties of the carbonbromine bond in 1-bromo-1-fluoroethane are evaluated from the observed nuclear quadrupole coupling constants. These molecular properties are compared with those of other related molecules. The molecular structure of 1-bromo-1-fluoroethane is found to be very close to that of 1,1-difluoroethane except for the C-Br bond.