No abstract

The far-infrared and Raman spectra of four isotopic species of cyclopentene have been assigned in order to obtain a detailed energy map for the low-frequency ring modes. The data for each molecule, consisting of a main series of ring-puckering bands, a series of side bands, and a series of ring-twisting absorption peaks (for the asymmetrically deuterated d1 and d4 molecules), have been analyzed by means of a two-dimensional potential energy calculation. The calculation yields a potential function of V = 7.880 X 10%4 -0.2706 X 10%2 + 0.5158 X 10%2 + 1.904 X 10%%2, where x1 and x2 represent the ring-puckering and ring-twisting coordinates, respectively. The barrier to inversion is calculated to be 232 cm'1 and the sign of the cross term reflects the fact that twisting of the ring tends to hinder the puckering process.

No abstract

More than 25 ring-puckering transitions have been observed in the vapor-phase Raman and far-infrared spectra of cyclopentene-d8. The ring-puckering potential energy function in reduced form was determined to be V=18.20(Z4−6.88 Z2) cm−1 which represents a barrier to inversion of 215 cm−1 (0.61 kcal/mole). The barrier differs from that of the undeuterated cyclopentene by 17 cm−1 owing to mixing of other motions (presumably CH2 rockings). The equilibrium value of the molecule is calculated to have a dihedral angle of 26°.

Articles you may be interested inDetermination of the conformational barriers to internal rotation of 3fluoropropene from far infrared and low frequency Raman spectra J. Chem. Phys. 81, 4259 (1984); 10.1063/1.447434 Microwave, Raman, and far infrared spectra, barrier to internal rotation, and dipole moment of 2,2difluoropropane J. Chem. Phys. 74, 5946 (1981); 10.1063/1.441032 Raman spectra and outofplane ring vibrations of bicyclo [3.1.0] hexane and its analogs