V. K. Matveev

Vibrational spectra and conformational analysis of five chlorosubstituted buta-1,3-dienes

Abstract A complete interpretation of the vibrational spectra of chloroprene, 2,3-dichlorobuta-1,3-diene, 1,1,2,3-tetrachlorobuta-1,3-diene, 1,1,2,3,4-pentachlorobuta-1,3-diene and hexachlorobuta-1,3-diene has been carried out and a normal coordinate analysis of these molecules has been performed. The conclusion about the non-planar conformation of the last three molecules was drawn from results of the CNDO/2 conformational calculations. The applicability of the CNDO/2 method to the molecules with the conjugated double bonds is discussed.

A dielectric study of the structure of propylene glycol

The dielectric spectra of propylene glycol over the frequency and temperature ranges 10 mHz–75 GHz and 175–423 K, respectively, were analyzed using the Dissado-Hill cluster model. A correlation between relaxation processes of breaking and formation of intermolecular H-bonds in clusters was obtained. A correlation of fluctuation processes of synchronous exchange of molecules between neighboring clusters corresponded to the redistribution of H-bonds between them. The Dissado-Hill theory was used to determine the integral relaxation times, nDH and mDH parameters and calculate the mean dipole moments of propylene glycol clusters and the energy characteristics of processes of their rearrangement. The mean dipole moments of clusters (23617–18.65 D) were compared with those of molecules in the liquid phase (3.67–3.03 D). The apparent activation enthalpy of processes of cluster rearrangements decreased from 141.8 to 25.2 kJ/mol, the activation energy decreased from 46.03 to 18.47 kJ/mol, and the energy of orientation dipole-dipole interactions, from 3.78 to 3.45 kJ/mol as the temperature increased.

An analysis of the vibrational structure of the UV absorption spectrum of methacryloyl chloride vapor

An analysis of the vibrational structure of the UV spectrum of methacryloyl chloride vapor was performed. The spectrum contained unique information about the torsional vibration levels of the trans and cis isomers in the ground (S0) and excited (S1) electronic states. 136 absorption bands were revealed, and ∼85% of them were assigned. The 0-0 transition frequencies of the trans and cis isomers were found. Several Deslandres tables were constructed for torsional vibrations from 0-0 transition frequencies and “local origins” corresponding to fundamental and combined frequencies of both isomers. Systems of torsional levels up to high quantum number values (v ≈ 6–8) were determined, and the ωe harmonic frequencies and χ11 anharmonicity coefficients were calculated for both isometric forms in the ground (S0) and excited (S1) states. The results were substantially different from those obtained in an analysis of Fourier-transform IR spectra.

An analysis of the vibrational structure of high-resolution UV spectra and long-wave IR Fourier transform spectra in studies of internal rotation in molecules

The methods for analyzing the vibrational structure of high-resolution UV spectra and long-wave IR Fourier transform spectra in studies of internal rotation in α,β-unsaturated carbonyl compounds R4R3C=CR2-COR1 (R1 = F, Cl; R2 = R3 = R4 = H, CH3) are compared. These methods were found to give different experimental values for systems of torsional vibration energy levels up to high quantum numbers, torsional frequencies (0–1 transitions), and anharmonicity coefficients x11 for trans and cis isomers of the same molecules in the ground electronic state (S0). It was shown that the experimental technique for analyzing the vibrational structure of UV spectra excludes the hydrolysis of compounds under study. Taking into account Fermi resonance and numerous Deslandres tables constructed for trans and cis isomers provides reliable determination of values necessary for the construction of internal rotation potential functions, because they are multiply repeated in various Deslandres tables. An analysis of the vibrational structure of UV spectra gives more reliable Vn internal rotation potential function parameters. The Vn parameter values were substantiated by quantum-mechanical calculations performed by other authors.

Relaxation processes of the structural rearrangement of clusters in liquids: 1,2-ethanediol, 1,2-propanediol, and 1,2,6-hexanetriol

The dielectric relaxation spectra (DRS) of 1,2-ethanediol, 1,2-propanediol, and 1,2,6-gexanetriol are analyzed in terms of the Dissado-Hill (DH) model in a wide range of temperatures, with all parameters required for calculating the cluster dipole moments being determined within the DH molecular model itself. The dependence of the equilibrium and relaxation properties of DRS on the hydrocarbon radical length and the number of OH groups is studied. The dipole moments of the clusters are calculated. It is shown how the roles of the processes of intracluster rearrangement are redistributed due to the break of hydrogen bonds and fluctuation processes of synchronous exchange of molecules between the clusters.

Correlation between the equilibrium and relaxation dielectric properties of 1,2-ethanediol

AbstractThe data on the dispersion of the permittivity ɛ*(ω) of 1,2-ethanediol over the temperature range 161–453 K and the frequency range 0.1 Hz–150 GHz were analyzed using the Dissado-Hill cluster model. The relaxation frequency ωp = τDH−1 and intra-(nDH) and intercluster (mDH) correlation parameters were calculated. The energy barrier to the libration of molecular axes in clusters was found to be BDH = 2.96 kJ/mol. The apparent enthalpy of activation was determined; it increased from ΔHDH exp# = 22.18 kJ/mol to ΔHDH exp# = 129.19 kJ/mol close to the glass transition temperature. The mean dipole moments

Comparative analysis of the vibrational structure of the absorption spectra of acrolein in the excited (S 1) electronic state

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Molecular dynamics models and thermodynamic characteristics of hydrogen bonds in 1,2-ethanediol

of 1,2-ethanediol clusters were calculated; they decreased from 162920 to 18.08 D as the temperature increased from 161 to 453 K. According to approximate estimates, the number of 1,2-ethanediol molecules in a cluster