The theory of rotational-pucker-vibrational transitions in the vibrational spectrum of cyclobutane is reviewed. Puckering sideband structure on the 1453 cm-1 v 14 infra-red fundamental of C4H8 has been observed and analysed, in terms of two slightly different puckering potential functions for the ground and the excited vibrational states. The results have been fitted to quartic-quadratic potential functions in the puckering coordinate, with a barrier to inversion of 503 cm-1 (1·44 kcal mole-1 = 6·02 kJ mole-1) in the ground state and 491 cm-1 in the excited state ν 14 = 1. For reasonable assumptions about the reduced mass, the equilibrium dihedral angle of the C4 ring is determined to be about 35°, in agreement with previous estimates. Ueda and Shimanouchi's observations on the 2878 cm-1 C4H8 band have been re-analysed, and puckering sidebands have also been observed and analysed for the 1083 cm-1 v 14 infra-red fundamental of C4D8. Pure puckering transitions have been observed in the Raman spectrum of C4...

Puckering structure in the infra-red spectrum of cyclobutane

Ir and UV-vis spectroscopic studies of the stable MoCH2 carbene complexes over photoreduced silica-molybdena catalysts with chemisorbed cyclopropane, and their role in olefin metathesis reactions

The ring-puckering vibration of cyclobutane and cyclobutane-d8 in their gas phase Raman and infrared spectra

The far‐infrared spectrum of 2,3‐dihydrofuran vapor has been examined from 33 to 500 cm−1. Twelve sharp Q branches have been observed between 70 and 350 cm−1. These bands are assigned to transitions of the anharmonic ring‐puckering vibration which is described by the following relation in reduced coordinates: V(cm−1) = 28.3(x4 − 3.44 x2). Such a potential predicts a puckered molecule in the ground and first excited states, a barrier to planarity of 83 cm−1, and a 0–1 transition of 20.5 cm−1. There is considerable disagreement between the previously predicted far‐infrared spectrum and that observed.

Ring‐Puckering Vibration of 2,3‐Dihydrofuran

Raman spectra of polycrystalline acetone and acetone-d6

The infrared and Raman spectra of trimethylene selenide (TMSe) and trimethylene selenide‐2,2,4,4‐d4 (TMSe‐d4) have been recorded from 4000 to 15 cm−1 in gaseous, liquid, and solid states. A vibrational assignment of the fundamentals is consistent with the expected Cs equilibrium configuration. A series of sharp bands associated with the ring puckering vibration have been observed in the mid‐ and far‐infrared regions. The frequencies of the transitions have been employed in determining the following double‐minimum potential, barrier‐to‐ring inversion, and the equilibrium separation of the ring diagonal, 2x in angstroms, for TMSe, respectively: V(cm−1 = 4.258 (± 0.02) × 105x4 − 2.5391 (± 0.007) × 104x2; 378.1 ± 4 cm−1; 0.35 A. For TMSe‐d4 these quantities are: V(cm−1) = 3.242(± 0.1) × 105x4 − 2.208 (± 0.033) × 104x2; 375 ± 10 cm−1; 0.37 A, respectively. The dihedral angle of both molecules is calculated to be 32.5 ± 2°.

Vibrational Spectra and Structure of Four‐Membered Ring Molecules. XIV. Vibrational Analysis and Ring Puckering Vibration of Trimethylene Selenide and Trimethylene Selenide‐d4

J. R. Durig

Papers

Vibrational Spectra and Structure of Four‐Membered Ring Molecules. XIV. Vibrational Analysis and Ring Puckering Vibration of Trimethylene Selenide and Trimethylene Selenide‐d4

Vibrational Spectra and Structure of Four-Membered Ring Molecules. V. Ring-Puckering Vibration of Trimethylene Selenide