The Vibrational Assignments of Propyl Bromide and Its Two Asymmetrically-Deuterated Species

The vibrational assignments of the observed spectra of propyl bromide and its two asymmetrically-deuterated species have been worked out. Since the two gauche isomers come not to be equivalent for the asymmetrically-deuterated species, the infrared bands of the gauche isomer can be expected to be split into doublets, while the bands of the trans isomer remain singlets. The observed infrared bands for the gauche isomer were actually the doublets for the C–Br stretching and two CH2 rocking modes. The C–D stretching and deformation modes of the β-deuterated species were also in the expected spectral patterns. In order to confirm the vibrational assignments, the normal vibration calculation was carried out using a modified Urey-Bradley force field for the parent and two asymmetrically-deuterated species.