Dipole forbidden, nuclear electric quadrupole allowed transitions and chirality: The broadband microwave spectrum and structure of 2-bromo-1,1,1,2-tetrafluoroethane

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The chirped pulse Fourier transform microwave spectrum of the chiral molecule 2-bromo-1,1,1,2-tetrafluoroethane has been observed in the 6–18 GHz region of the electromagnetic spectrum and is reported. Six isotopologues, including 13C isotopic substitution at each carbon atom in both the 79Br and 81Br parent species have been observed in natural abundance. All rotational constants, quartic centrifugal distortion contants, and nuclear quadrupole coupling tensor components have been experimentally determined and have been reported. In addition, spin-rotation components Maa, Mbb, and Mcc are also determined and reported. The theoretical structure of the species has been determined and reported. The C–C–Br backbone structure has been determined experimentally implementing both Kraitchman single and Rudolph double substitution analysis, the later being explained in the text. 3440 transitions total have been observed with 45 transitions being electric dipole forbidden. These dipole forbidden transitions have been identified as they are planned to be used in microwave three-wave mixing experiments in order to better understand their role, if any, in determining chirality. The determined nuclear electric quadrupole coupling tensor has been diagonalized and compared to similar small alkane species in order to make inferences on the effects of fluorination on the C–Br bond.

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Journal of Molecular Structure



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