Masaaki Sugie

Structure of dichlorine monoxide as studied by microwave spectroscopy. Determination of equilibrium structure by a modified mass dependence method

Abstract The microwave spectra of four isotopic species of dichlorine monoxide (OCl2) have been observed, and the rotational constants have been obtained. The rm structure for each isotopic species has been determined by Watsons method. The equilibrium structure has been estimated by taking proper averages of rm structures to be r e (OCl) = 1.69587(7) A and ∠eClOCl = 110.886(6)°. The general applicability and the merit of the present method for estimating the equilibrium structure are pointed out.

The rotational spectra, molecular structure, dipole moment, and hyperfine constants of HOBr and DOBr

Abstract Pure rotational spectra of the 79Br and 81Br isotopic species of gaseous hypobromous acid, HOBr and DOBr, as well the v3 = 1 excited state of HOBr have been observed and analyzed. Structural parameters have been derived from the ground state rotational constants. The permanent molecular dipole moment of DOBr and the bromine nuclear quadrupole coupling and spin rotation constants of all the species have been determined.

Microwave spectrum of aminoborane, BH2NH2

Abstract The unstable species aminoborane, BH2NH2, has been identified as a reaction product of ammonia with diborane by microwave spectroscopy. The rotational constants determined are A = 138212 ± 4 MHz, B = 27487.83 ± 0.10 MHz and C = 22878.44 ± 0.11 MHz for 11BH2NH2 and A = 138199 ± 6 MHz, B = 28420.36 ± 0.11 MHz and C = 23520.78 ± 0.12 MHz for 10BH2NH2. The dipole moment is 1.844 ± 0.015 D.

Microwave spectrum and molecular structure of aminoborane, BH2NH2

Abstract The microwave spectra of five isotopic species of aminoborane have been observed. The rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants of 11B and 14N were determined from the spectra. The planarity and symmetry of the molecule were confirmed by the measurements of inertia defects, dipole components, and statistical spin weight due to the four hydrogen nuclei. The complete rs structure determined from the rotational constants is: r (BN) = 1.391(2) A , r (BH) = 1.195(4) A , r (NH) = 1.004(2) A , ∠HBH = 122.2(2)°, and ∠HNH = 114.2(2)°.

Ab initio investigation on the reaction path and rate for the gas‐phase reaction of HO + H2O ↔ H2O + OH

This article describes an ab initio investigation on the potential surfaces for one of the simplest hydrogen atom abstraction reactions, that is, HO + H2O ↔ H2O + OH. In accord with the findings in the previously reported theoretical investigations, two types of the hydrogen‐bonding complexes [HOHOH] and [H2OHO] were located on the potential energy surface. The water molecule acts as a hydrogen donor in the [HOHOH] complex, while the OH radical acts as a hydrogen donor in the [H2OHO] complex. The energy evaluations at the MP2(FC) basis set limit, as well as those through the CBS‐APNO procedure, have provided estimates for enthalpies of association for these complexes at 298 K as −2.1 ≈ −2.3 and −4.1 ≈ −4.3 kcal/mol, respectively. The IRC calculations have suggested that the [H2OHO] complex should be located along the reaction coordinate for the hydrogen abstraction. Our best estimate for the classical barrier height for the hydrogen abstraction is 7.8 kcal/mol, which was obtained from the CBS‐APNO energy evaluations. After fitting the CBS‐APNO potential energy curve to a symmetrical Eckart function, the rate constants were calculated by using the transition state theory including the tunneling correction. Our estimates for the Arrhenius parameters in the temperature region from 300 to 420 K show quite reasonable agreement with the experimentally derived values.

Molecular structures of 2,2-dihalogenopropanes by microwave spectroscopy: CH3CF2CH3, CH3CCl2CH3, and CH3CClFCH3

Abstract The microwave spectra of various isotopic species of 2,2-difluoro-, 2,2-dichloro-, and 2-chloro-2-fluoropropane have been observed and analyzed to obtain the rotational, centrifugal distortion, and chlorine quadrupole coupling constants. The electric dipole moment of 2,2-dichloropropane has been determined by measurement of the Stark effect. Using the obtained structural parameters, the changes in bond lengths with adjacent atoms or substituted groups are discussed.

Gas phase infrared spectrum of syn-vinyl alcohol produced by thermal decomposition of several alcohols and aldehydes

Abstract The gas phase infrared spectrum of the vinyl alcohol molecule, which is frequently obtained as a reaction intermediate in the pyrolyses of various alcohols and aldehydes, has been observed and analyzed. The pyrolytic reaction mechanisms of several alcohols and aldehydes have been investigated by monitoring the spectrum of vinyl alcohol. The molecular constants were determined by analyzing a 0.016 cm −1 resolution FTIR spectrum of the ν 13 vibration-rotation band. Ten fundamental absorption bands have been observed in 3600-600 cm −1 and their frequencies are in agreement with those obtained by a matrix isolation method.

Equilibrium structure and anharmonic potential function of phosgene: Microwave spectra of vibrationally excited states

Abstract The vibrational satellites in the microwave spectra of 35 Cl 2 CO were measured and analyzed for the ν 2 , ν 3 , 2 ν 3 , ν 4 , ν 5 , ν 6 , and ν 2 + ν 3 states. The rotational constants for the ν 5 state were first estimated by an analysis of anharmonic potential constants derived from the available rotational constants for the other excited states and other isotopic species and the electron diffraction intensity, and used for the assignment of its weak satellites. The Coriolis resonance between ν 2 and ν 4 was analyzed, and the difference in their wavenumbers, ν ∼ 4 − ν ∼ 2 = 9.553(3) cm −1 , was obtained. The sign of the perturbation (positive) was determined using the infrared band envelope.

Microwave spectra of dichlorine monoxide in its excited vibrational states

Abstract The microwave spectra of dichlorine monoxide (Cl 2 O) in its excited vibrational states were measured in the frequency range 12–56 GHz. The Coriolis interaction between the v 1 and v 3 states was analyzed and the following equilibrium rotational constants and equilibrium structure were obtained: A e = 41 938.9(4) MHz, B e = 3704.73(4) MHz, C e = 3404.07(4) MHz, r e (OCl) = 1.695 9(1) A , and ∠ e (ClOCl) = 110.88(1)°. The off-diagonal element X ah of the nuclear quadrupole interaction constant was determined by the analysis of anomalies observed in the hyperfine splittings.

Correlation between hardness and activation energies for reactions of OH radical with halomethanes

Abstract The density functional theory based descriptor of reactivity, hardness, correlates well with the activation energies for a series of hydrogen atom abstraction reactions between the hydroxyl radical and halomethane compounds. A good correlation has also been observed for simple haloethane compounds.