Yonezo Morino

Average structures of butadiene, acrolein, and glyoxal determined by gas electron diffraction and spectroscopy

Abstract The structures of butadiene, acrolein, and glyoxal have been investigated with the main purpose of studying the variation in the lengths of the central C-C bonds. In order to derive as reliable structures as possible, the electron diffraction intensities obtained in the present study and the rotational constants for several isotopic species reported in the literature have been analyzed by a least-squares method which combines them as joint observables. The method is based on the conversion of the electron-diffraction r a distances into the r ° α distances and that of the effective ground-state rotational constants into the average rotational constants.

Calculation of inertia defect: Part I. General formulation

Abstract A general formula for inertia defect of a molecule is presented following Nielsens theory of vibration-rotation interaction. The expression was simplified by the use of general properties of 1 matrix which transforms the normal coordinates to the Cartesian coordinates. The effects due to the centrifugal distortion and the electronic interaction were also taken into account. Some examples of the calculation are given for H 2 O- and H 2 CO-type molecules.

Coriolis interaction and anharmonic potential function of ozone from the microwave spectra in the excited vibrational states

Abstract Microwave absorption spectra of ozone were identified in the excited vibrational states with v1 = 1, v2 = 1 and 2, and v3 = 1. In the v1 = 1 and v3 = 1 states, an anomaly due to a strong Coriolis interaction was observed. The inertia defect in the Coriolis perturbed states was defined and successfully applied to the analysis. The Coriolis coupling constant ζ13c was determined to be 0.60, from which the quadratic force constants were derived. The cubic potential constants (and third-order force constants) were determined from the vibration-rotation interaction constants obtained. The quartic potential constants were derived from the vibrational anharmonic constants by McCaa and Shaw. Close similarities were observed among the anharmonic potential constants of ozone, sulfur dioxide, and oxygen difluoride. The equilibrium structure and average structures in the ground and excited vibrational states were obtained.

The role of isotopic differences in the determination of molecular structure. A supplementary note on the structure of acrolein

Abstract The discrepancy between the r a o and r z structures of acrolein reported in a previous study has been removed by taking into account small isotopic differences in the distances among the carbon and oxygen atoms. The effect of uncertainties in the isotopic differences on the determination of the average structure is examined, and a general method for deriving the best possible structure from electron-diffraction and spectroscopic data is suggested. The r g bond distances in butadiene, acrolein, and glyoxal are compared with one another.

Effect of vibration and rotation on the internuclear distance

Abstract The effect of vibration and rotation of a molecule on the internuclear distances is calculated to the second order of approximation. A general formula for the expectation value is obtained including the effects coming from the anharmonicity of vibration as well as from the centrifugal force. Coriolis coupling has influence neither on the internuclear distances in the ground state nor on the averaged distances in the thermal equilibrium. Convenient expressions for the centrifugal distortion are considered by making use of vector notations. Actual calculation for individual molecules has revealed many changes in the average positions of the nuclei, particularly in the molecules containing hydrogen atoms. The statistical average of the internuclear distance in thermal equilibrium is calculated. It is seen that the change in the internuclear distance due to centrifugal distortion is proportional to the temperature. The anharmonic vibrational effect is more significant than the centrifugal distortion.

Mean Square Amplitudes and Force Constants of Tetrahedral Molecules. I. Carbon Tetrachloride and Germanium Tetrachloride

The atomic distances and mean square amplitudes of carbon tetrachloride and germanium tetrachloride were measured by the sector‐microphotometer method of electron diffraction. The force constants were calculated by use of the mean square amplitudes thus obtained, combined with the normal frequencies. The results indicate that a force field of the Urey‐Bradley type is approximately realized in these molecules.

Equilibrium structure and potential function of sulfur dioxide from the microwave spectrum in the excited vibrational state

The microwave spectra of the SO2 molecule were measured in the first excited states of all the normal vibrations as well as in the second excited state of the ν2 vibration. The quadratic force constants are calculated from the inertia defects in the excited vibrational states, and the cubic and quartic constants are determined through the changes of the rotational constants by the excitation of the vibrations, combined with the anharmonicity constants of the vibrational frequencies, xijs, reported by Nielsen et al. The re structure was determined definitely and compared with various structures such as rz, rs, and ro

Microwave spectrum and rotational isomerism in butene-1

Abstract The butene-1 molecule exists in two rotational isomers, the cis and the skew forms. The rotational constants of these isomers in the ground vibrational states were found to be A = 15 302.54, B = 5 574.92, and C = 4 303.14 MHz for the cis form and A = 22 557.33, B = 4 156.28, and C = 4 056.21 MHz for the skew form. The dipole moment was obtained through the Stark effect: μ a = 0.368 ± 0.004, μ b = 0.237 ± 0.006 and μ t = 0.438 ± 0.007 D for the cis and μ a = 0.345 ± 0.007, μ b = 0.081 ± 0.011, μ c = 0.059 ± 0.016 and μ t = 0.359 ± 0.011 D for the skew form. The structures of both forms were determined from the rotational constants of the deuterated as well as of the normal species. An opening of the skeletal CCC angles of the cis form was concluded and ascribed to intramolecular repulsion between the methyl and vinyl groups. The skew forms of a number of deuterated species show an anomalous Stark effect, which makes it possible to determine the rotational constant A . The barrier hindering the internal rotation of the methyl group was found to be 3.16 kcal/mole for the skew form, whereas a remarkable increase to 3.99 kcal/mole was obtained for the cis form. This high barrier is probably due to the repulsion between the methyl and vinyl hydrogen atoms. For the skew form, the effect of tunneling through the trans barrier was observed in the rotational spectra in the excited states of the CC torsion.

The Mean Amplitudes of Thermal Vibrations in Polyatomic Molecules. I. CF2=CF2 and CH2=CF2

A normal coordinate treatment based on the potential function of Urey‐Bradley type has been applied to CF2=CF2 and CF2=CH2 molecules by taking into account the repulsions between nonbonded atoms in addition to the valence force field. The mean‐square amplitudes of thermal vibration of the atomic distances in these molecules have been calculated by the use of the normal coordinates and compared with those obtained by I. Karle and J. Karle from the electron diffraction investigation.

Band contour analysis of the ν1 and ν5 fundamentals of formaldehyde

Abstract Infrared ν 1 and ν 5 bands of H 2 CO in the CH stretching frequency region were measured with the resolution of 0.3 cm −1 . Rotational structures of these bands were analyzed as asymmetric-top bands by means of band-contour calculations and least-squares fits. The band origins and the rotational constants of the upper states were determined. The band origin of ν 5 , 2843.24 ± 0.03 cm −1 , is in good agreement with that obtained by Blau and Nielsen using a symmetric-top approximation, whereas the ν 1 band origin, 2782.40 ± 0.07 cm −1 , is significalnty higher than the value 2766.4 cm −1 assigned by them. Small anomalous shifts were observed in the ν 1 band, indicating the presence of Coriolis interactions with other states. Possible cases are discussed. Equilibrium rotational constants were calculated by the use of the α constants determined in our present and previous studies, and the r e structure was estimated to be r e (CH) = 1.099 ± 0.009 A , and φ e (HCH) = 116.5 ± 1.2°, on the assumption that r e (CO) = 1.203 ± 0.003 A .