Microwave Spectrum, Nuclear Quadrupole Coupling Constants, and Structure of Bromodifluoromethane

Abstract

The microwave spectrum of bromodifluoromethane, CHBrF2(Halon 1201) has been studied for the first time from 7 to 40 GHz. A least-squares analysis of the observedc-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:A= 10199.7186(62) MHz,B= 2903.4150(26) MHz,C= 2360.1521(23) MHz, ΔJ= 0.660(14) kHz, ΔJK= 2.87(11) kHz, ΔK= 8.95 kHz, δJ= 0.1344(24) kHz, δK= 3.22(15) kHz, χaa= 521.281(92) MHz, χbb− χcc= −38.32(9) MHz, and |χac| = 187.1(26) MHz for the79Br species;A= 10199.5567(54) MHz,B= 2876.5588(20) MHz,C= 2342.3796(18) MHz, ΔJ= 0.652(12) kHz, ΔJK= 2.77(9) kHz, ΔK= 8.21(61) kHz, δJ= 0.1300(19) kHz, δK= 2.97(13) kHz, χaa= 435.61(10) MHz, χbb− χcc= −32.08(8) MHz, and |χac| = 148.5(29) MHz for the81Br species. The structural parameters are calculated from all these rotational constants and the electronic properties of the carbon–bromine bond in bromodifluoromethane are evaluated from the observed nuclear quadrupole coupling constants. These molecular properties are compared with those of other related molecules.