Earlier Electron Diffraction Research Articles

High-resolution infrared studies of perdeutero-spiropentane, C5D8

Perdeutero-spiropentane (C5D8) has been synthesized, and infrared and Raman spectra are reported for the first time. Wavenumber assignments are made for most of the fundamental vibrational states. Gas phase infrared spectra were recorded at a resolution (0.002cm−1) sufficient to resolve individual rovibrational lines and show evidence of strong Coriolis and/or Fermi resonance interactions for most bands. However a detailed rovibrational analysis of the fundamental ν15 (b2) parallel band proved possible, and a fit of more than 1600 lines yielded a band origin of 1053.84465(10)cm−1 and ground state constants (in units of cm−1): B0=0.1120700(9), DJ=1.51(3)×10−8, DJK=3.42(15)×10−8. We note that the B0 value is significantly less than a value of Ba=0.1140cm−1 calculated using structural parameters from an earlier electron diffraction (ED) study, whereas one expects Ba to be lower than B0 because of thermal averaging over higher vibrational levels. A similar discrepancy was noted in an earlier study of C5H8 (Price et al., 2011). The structural and spectroscopic results are in good accord with values computed at the anharmonic level using the B3LYP density functional method with a cc-pVTZ basis set.

The microwave spectrum and structure of allyl alcohol

The microwave spectrum of the normal species of the gauche, gauche isomer of allyl alcohol has been reassigned and rotational and centrifugal distortion constants have been determined. Rotational constants of nine deuterated species three carbon-13 species and the oxygen-18 species have also been obtained. These data were used to estimate structural parameters by least-squares fitting of the effective moments of inertia. Good agreement with an earlier electron diffraction and ab initio study was obtained. Unassigned transitions from another isomer were observed, presumably the cis, gauche conformer.

ChemInform Abstract: THE MICROWAVE SPECTRUM OF SILYL ISOCYANATE, SIH3NCO: SPECTRA OF ISOTOPICALLY SUBSTITUTED SPECIES AND CORRECTION OF THE RS STRUCTURE

Abstract Microwave spectra have been measured for 10 isotopic species of silyl isocyanate, SiH3NCO, in the ground vibrational state, and in several excited states of the lowest frequency bending vibration, ν10. This vibration is highly anharmonic, with a potential hump of 31.5 cm−1 at the linear configuration, and its effects have been removed from the rotational constants to produce effective ground-state rotational constants B 0 ∗ for each isotopic species. These B 0 ∗ constants have been used to determine the structural parameters, which are now in good agreement with earlier electron diffraction values. Excellent predictions have been made of the centrifugal distortion constants for different isotopic species and vibrational states, as well as of the l-type doubling constants of the various isotopic species.