Bis(dichlorosilyl)methylamine – Synthesis,Crystal Structure,and Conformational Analysis in the Gas Phase

A straightforward preparation has been found for bis(dichlorosilyl)methylamine, (SiHCl₂)₂NMe ( 1 ), involving reaction between H₂NMe and an excess of SiHCl₃, dissolved either in pentane or THF at 253 K. 1 and a side‐product, 1,3,5‐trichloro‐2,4,6‐trimethylcyclotrisilazane, (–SiHCl–NMe–)₃ ( 2 ), were identified by elemental analysis, mass spectrometry and ¹H‐NMR‐spectroscopy. Some physical, NMR‐ and IR spectroscopical properties of 1 were determined. The molecular and crystal structure of 1 was investigated by single crystal X‐ray diffraction. Selected structural parameters: r(Si–N) 169.7(5), r(Si–Cl) 203.1(2)–204.4(2), r(C–N) 150.0(8) pm; a(SiNSi) 123.6(3), a(SiNC) 118.3(4)/118.0(4)°. Ab initio force field data and infrared intensities were calculated for four conformers of 1 . Comparison of the observed and calculated IR spectra favours the two structures found ab initio provided that their actual abundancies are different from those calculated.     

Microwave spectrum,centrifugal perturbation,dipole moment,and conformation of 5-methyl-1,3-dioxane

The microwave spectrum of 5-methyl-1,3-dioxane was studied in the frequency range 12–35 GHz. The a and c type rotation transitions with J≤30 were identified. The rotational constants A = 4658.5244(33) MHz, B = 2383.3930(12) MHz, and C = 1724.28907(88) MHz and the quartic constants of the centrifugal distortion of the molecule in the ground vibrational state were determined. The components of the dipole moment were found, μ _a = 1.76 ± 0.01 D and μ _c = 1.10 ± 0.01 D; the net dipole moment of the molecule is μ = 2.08 ± 0.01 D. 5-Methyl-1,3-dioxane was calculated by the B3PW91/aug-cc-pVDZ density functional theory method. The calculated data are compared with the experimental data. The most stable conformation is the chair conformation with an equatorial orientation of the methyl group.     

Photoinduced Oxidation Reaction of Benzotrifluoride with OH Radical by the Laser Flash Method

The optical transient and kinetics characterizations of the transients formed in the reaction of OH with benzotrifluoride (BTF) were performed by a laser flash photolysis technique. The results indicated that the formation of π‐type adduct of C₆H₅(OH)CF₃ was the major reaction channel, and the δ‐type adduct of C₆H₅CF₃OH formation was an additional minor process in the oxidation reaction of BTF attacked by OH radicals yielded from the photolysis of H₂O₂. Addition of OH to the CF₃ group led to the fluoride ion elimination to yield α,α‐difluorophenylcarbinol (C₆H₅CF₂OH). Trifluoromethylphenol (HOC₆H₄CF₃) of meta‐, para‐ and ortho‐substituted isomers resulted from the addition of OH to the BTF aromatic ring.     

Interrelationship of the Torsional and Rotational States of Asymmetric Nonrigid Molecules

The incorrectness of solution of a torsional-rotational equation for asymmetric nonrigid molecules in the system of internal axes is shown; this incorrectness is caused by the broken interrelationship between the torsional quantum number and the parity of the rotational quantum number K.     

Formation of Metallophthalocyanine Trimers in Liquid Solutions

For solutions of the complexes of phthalocyanine (PhC) with magnesium (Mg-PhC) and of tetrachloromethyl-PhC with zinc (Zn-PhCCh) in mixtures of glycerin with dimethyl formamide (DMF) and for Zn-PhCCh in toluene and DMF it has been found that the electron absorption spectra substantially depend on the substance concentration. It is shown that these changes are attributable to the association of the molecules of pigments. The number of molecules in the associates and the equilibrium constants for this association are determined. The formation of the trimers of Mg-PhC in binary solutions and the dimers of Zn-PhCCh in toluene, DNF, and binary solutions has been established. It has been found that on association the Q absorption bands of the pigments shift to shorter wavelengths as compared to the bands of the monomers. For the Mg-PhC trimers, the shift is = 1410 cm^–1, while for the Zn-PhCCh dimers it is 990 cm^–1 in toluene, 930 cm^–1 in DMF, and 925 cm^–1 in the mixture of DMF with glycerin. It is concluded that the structure of the trimers and dimers is of the type of a stack in which molecules are arranged in parallel one above the other at a distance of 3.5 to 4.0 Å between the planes of the molecules. In association, the fluorescence intensity of the pigments decreases substantially (the decrease corresponds to the decrease in the concentration of the monomer molecules of phthalocyanines), with the fluorescence spectra remaining unchanged. Consequently, the associates of the pigments do not display pronounced fluorescence.     

Effect of Deuteration on Quasiline Electronic‐Vibrational Spectra of Phthalocyanine

Quasiline electronicvibrational spectra of fluorescence and absorption (excitation of fluorescence in selective recording) of the molecules of phthalocyanine deuterated around the periphery of benzene rings (H₂Phcd ₁₆) and the center of the macrocycle (D₂Phc) are obtained. The vibrational frequencies of the ground state are almost insensitive to this deuteration (except for vibrations with the participation of angular deformations). In excitation spectra, changes in deuteration are more pronounced due to the effects of nonadiabatic vibronic interaction of the vibrational sublevels of the S ₁ state and of the purely electronic level S ₂.     

Optical Reflection Spectrum of the Human Tympanic Membrane

The results of an investigation of the reflection spectrum of the human tympanic membrane in the visible and near IR ranges ( = 400–900 nm) are reported.     

Nuclear hyperfine coupling interactions in the rotational spectra of the linear and bent isomers of HF-N2O

The rotational spectra of six isotopomers of the linear and bent isomers of HF-N₂O have been collected in the 7-18 GHz region with a Fourier transform microwave spectrometer. The nuclear hyperfine structure in the spectra produced by HF spin-spin coupling interaction and nuclear quadrupole coupling interactions due to the D nucleus of DF and the nuclei of N₂O have been resolved and analyzed. In the linear isomer, H in HF is bonded to the terminal N in N₂O. The NF bond lengths are 2.9808(2) Å for the HF-containing isotopomers and 2.9732(2) Å for the DF-containing isotopomers. The zero point angles are 23.1° for HF and 31-34° for N₂O. The hyperfine constants suggest that the HF bond is lengthened by 0.0105 Å upon complexation and that the electric field gradients of the two nitrogen nuclei in N₂O are perturbed differently in the complex. In the bent isomer, the hydrogen bond is formed between HF and O in N₂O. The intermolecular distances are 3.4942(2) Å for the HF-containing isotopomers and 3.4436(2) Å for the DF-containing isotopomers, with HF and N₂O forming angles of 34° and 46°, respectively, with the intermolecular axis. The nuclear quadrupole coupling constants of the two nitrogen nuclei do not indicate electric field gradient perturbation in this isomer.     

Quantum Spectrum of Some Anharmonic Central Potentials: Wave Functions Ansatz

Based on the ansatz to the wave functions, the quasi-exact solutions of the 2D Schrödinger equation with some anharmonic potentials are reviewed and analyzed if admitting restrictions on the parameters of the potential and the angular momentum m. These potentials are taken as the screened Coulomb potential V(r)=a/r+b/(r+), the singular one-fraction power one V(r)=ar ^–1/2+br ^–3/2 and the singular two-fraction one V(r)=ar ^2/3+br ^–2/3+cr ^–4/3. The latter one is found that the hidden symmetry exists if substituting r–ir. It will reverse the signs of E and c of quantum system, leaving the remaining parameters invariant.     

Absorption Spectra of Gasolines in the Region 1090–1220 nm

The difference absorption spectra of different grades of gasoline (A-76, AI-92, and AI-95) with octane numbers lying within 76–85 have been investigated experimentally in comparison with hydrocarbons: isooctane, benzene, and n-heptane. The spectra obtained contain absorption bands of the CH₃, CH₂, and CH groups and supposedly of the olefin double bond. The possibility of determining the octane number of an unknown grade of gasoline by using the absorption of a measured difference spectrum at one selected wavelength is shown.