Microwave spectrum of monohalogenated allenes: bromoallene
Abstract
The microwave spectrum of bromoallene for 79Br and 81Br species has been studied from 15 to 35 GHz. A least-squares analysis of the observed a- and b-type transition frequencies gave rotational, quartic centrifugal distortion constants and the components of the nuclear quadrupole coupling constants tensor in the principal axes system: A= 27 849.952 (63), B= 2009.8672 (40) and C= 1897.3682 (27) MHz, DJ= 0.705 (25), DJK=–46.1 (10), δJ= 0.0915 (29) kHz, χaa= 377.11 (94), χbb–χcc= 182.78 (13) and |χab|= 381.32 (24) MHz for 79Br species; and A= 27 820.459 (52), B= 1996.0270 (33) and C= 1884.8908 (22) MHz DJ= 0.632 (21), DJK=–46.5 (8), δJ= 0.0931 (16) kHz, χaa–χcc= 152.42 (10) and |χab|= 318.00 (16) MHz for 18Br species. The structural parameters are calculated from the observed rotational constants. The bond length C—Br in bromoallene was found to be longer than that in bromoethene, in accordance with lower π character for C—Br in bromoallene than in bromoethene.