Vibrational Assignment and Dipole Moment Derivatives of Liquid Bromobenzene at 25 °C

The previously published optical constants of bromobenzene were used to calculate the imaginary molar polarizability spectrum. The imaginary molar polarizability spectrum was fit to 163 classical damped harmonic oscillator bands between 3240 and 140 cm-1, the vast majority of which were obvious in the experimental spectrum. With the aid of the previous fundamental assignments in the literature and the force field for liquid benzene, the first thorough assignment of liquid bromobenzene is presented. The integrated intensities, transition moments, and dipole moment derivatives with respect to normal coordinates of the fundamentals were calculated from the fitted bands. These transition moments and dipole moment derivatives are compared with those in the literature for benzene-d. The transition moments and dipole moment derivatives are significantly different in these substituted benzenes, indicating that either the eigenvectors for the vibrations are different in the two molecules or that dipole moment derivatives with respect to internal coordinates are different in the two molecules. This will be analyzed further in a future paper.