The microwave spectrum, electric dipole moment, and bromine nuclear quadrupole coupling constants of 2-bromopyrimidine

Abstract

The microwave spectrum of 2-bromopyrimidine has been observed for the first time. For both the 79Br and 81Br isotopomers, R-branch transitions with J values ranging from 20 to 37 have been measured in the 38–75 GHz frequency range. Ground state rotational constants and values for four quartic distortion constants have been determined for both isotopomers. Hyperfine structure due to the presence of the quadrupolar bromine nucleus has been analyzed, yielding principal values of the quadrupole tensor as χ aa = 567.8(7), χ bb = −329(5), and χ cc = −239(5) MHz for the 79Br isotopomer and χ aa = 475.6(6), χ bb = −274(2), and χ cc = −201(2) MHz for 81Br. Our results demonstrate that the 2-bromopyrimidine molecule is planar and has C 2 V symmetry. The dipole moment of the molecule has been determined from Stark effect measurements to be 3.71(8) D.