Conformational structure of divinylacetylene

Ab initio quantum chemical calculations of the divinylacetylene molecule with different mutual orientations of vinyl groups are carried out using the 6–31G*/MP2 basis set. The torsional potential is approximated by a Fourier series. It is shown that the second term of the series dominates. The enthalpies of the cis- and trans-isomers are nearly equal; the maximum corresponds to the gosh-orientation (180.4 cm⁻¹ with respect to the cis-form). The vibrational spectra of the compounds with cis-, gosh-, and trans-orientations of vinyl groups are analyzed based on the ab initio calculations. It is concluded that the experimental data available in the literature agree with the hypothesis that divinylacetylene exists as cis- and trans-isomers. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 610–617, July–August, 1998.     

Kinetic and mechanistic study of the quasiliving cationic polymerization of styrene with the 2-phenyl-2-propanol/AlCl3 · OBu2 initiating system

The cationic polymerization of styrene with the 2-phenyl-2-propanol (CumOH)/AlCl₃ · OBu₂ initiating system at various dibutyl ether concentrations in a mixture of 1,2-dichloroethane and n-hexane (55:45 v/v) at −15 °C was investigated. The experimental results showed that an increase in dibutyl ether concentration leads to a noticeable decrease in the polymerization rate as well as to the more controlled polymerization in terms of molecular weight (M_n) and molecular weight distribution (MWD) evolutions. The kinetic investigation revealed that the polymerization proceeds in two stages. The first stage is characterized by high polymerization rate and slow initiation relative to propagation. During this stage molecular weight decreases or does not change and MWD increases with conversion. In the second stage considerably slower quasiliving polymerization of styrene occurs. The quasiliving nature of the styrene polymerization by the CumOH/AlCl₃ · OBu₂ system is proved and mechanistic scheme of the polymerization is proposed.     

Spectroscopic study of germanium-containing compounds

Conclusions The values of C=0 in the IR spectra and the position of the band from the n ^* electronic transition in the UV spectra of the amides R¹CONR²R³ vary linearly with the inductive effect of the R¹ substituent (for R²=R³=H, Alk). This may indicate the absence of the intramolecular coordination Ge 0, where or. The substituent R¹=Ge(C₂H₅)₂ exhibits electron-acceptor properties besides a +I-effect.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 349–352, February, 1984.     

Hoffmann's method applied to ethylene oxide,ethylenimine, cyclopropane,and cyclopeopyl ethers

The method is applied to six compounds each containing a three-membered ring. It is found that a cyclopropane ring interacts with ether oxygen attached to it to give some of the features of a -electron system. Inclusion of N or O in the three-membered ring lowers the top filled and bottom vacant levels, especially the latter.     

Silochroms as adsorbents and supports in liquid chromatography

The use of macroporous silica gels, silochroms, with homogeneous geometrical structure as adsorbents and supports for liquid stationary phases in liquid chromatography is described.

The selectivity of separation and retention volumes of silochroms depend strongly on the degree of hydroxylation of the surface and on the nature of the mobile phase. In optimizing the parameters, rapid and complete separation of strongly polar isomers and biological active substances and drugs is obtained.

The dependence of retention volumes and column efficiency on the amount of liquid phase, covered on silochrom, has been investigated.     

Singular and nonsingular three-body integrals for exponential wave functions

Integrals which are individually singular, but which may be combined to yield convergent expressions, are needed for computations of relativistic effects and various properties of atomic and quasiatomic systems. As computations become more detailed and precise, more such integrals are required. This paper presents general formulas for the radial parts of the singular and nonsingular (regular) integrals that occur when three-body systems are described using wave functions that include exponentials in all three interparticle coordinates. Our results are compared with those found in the literature for some of the integrals, and are also shown to be consistent with previously reported results for Hylleraas functions (a limiting case in which one of the exponential parameters is set to zero).     

Influence of solvent on ir spectra of aroyl(hydroxymethyl)trifluorosilanes

Conclusions Dipole-dipole interaction of the solvent with molecules of aroyl (hydroxymethyl) trifluorosilanes 4-XC₆H₄COOCH₂SiF₃ is responsible for changes in frequency of the stretching vibrations of groups included in a five-membered ring, containing an intramolecular coordination bond Si 0 (the frequencies C=O and SiF _a , are lowered, and the frequencies _asCOC are raised). The value of the orientation-induction parameter in the Buckingham equation, reflecting the dependence of C=O and SiF _a on the parameters of the medium (, n), increases with increasing electron-donor capability of the substituent X, indicating an increase in the strength of the coordination bond. The coefficient in the Hammett equation is determined by the polar properties of the medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2251–2254, October, 1984.