Far-infrared and Raman spectra and vibrational potential energy surface for the ring-puckering and ring-flapping of coumaran Academic Article uri icon

abstract

  • The far-infrared and Raman spectra of coumaran vapor have been recorded and analyzed. Single, double, and triple quantum jump transitions (P = 1, 2, 3) were observed in the 60-270 cm-1 region for the ring-puckering vibration in both the ground and first excited states of the ring-flapping vibration. These were utilized to assign the ring-puckering quantum states for both flapping states, allowing both one- and two-dimensional potential energy functions to be determined. The one-dimensional function in terms of the ring-puckering coordinate (x1) has the form V (cm-1) = (7.92 105)x14 - (2.99 104)x12 and has a barrier to planarity of 279 cm-1 (3.32 kJ/mol) with energy minima corresponding to dihedral angles of 30. The two-dimensional surface in terms of the puckering and flapping coordinates shows that there is extensive interaction between these two vibrations. The barrier for the two-dimensional surface is 275 cm-1, and the dihedral angle is 37. The coumaran barrier is considerably higher than that for 2,3-dihydrofuran (83 cm-1), which does not have the attached benzene ring.

published proceedings

  • JOURNAL OF PHYSICAL CHEMISTRY A

author list (cited authors)

  • Bondoc, E., Klots, T., & Laane, J.

citation count

  • 19

complete list of authors

  • Bondoc, E||Klots, T||Laane, J

publication date

  • January 2000