Determination of the Molecular Structure of 1-Bromo-2-Fluorobenzene Using Microwave Spectroscopy

Fourier-transform microwave (FTMW) spectroscopy is a technique used to determine the structure of molecules. FTMW spectroscopy can give a very precise measurement of molecular structure because it is able to precisely measure a molecule\u27s emission at varying frequencies, allowing for the calculation of the molecule\u27s moments of inertia. While this technique has been used extensively to determine the exact structure of many common molecules, it has never been applied to 1-bromo-2-fluorobenzene. We accomplished this by measuring the emission lines in the 8-18 GHz frequency range using FTMW spectroscopy and comparing them to a prediction generated using Gaussian, a computer program that gives theoretical rotational constants from complex mathematical calculations. The AABS software package was then used to visually compare the experimental spectrum to that of the theoretical prediction; the software allowed for assignments of quantum numbers and the determination of the experimental rotational and distortion constants within an overall rms error of .0040 MHz. This was done for one naturally occurring isotopologue of bromine. The three rotational constants of 1-bromo-2-fluorobenzene were determined to be the following: A 2836.5890(4), B 978.8707(1), C 727.6323(1). Centrifugal distortion and quadrupole coupling constants will also be reported