NMR spectroscopic study of the effects of conjugation

Conclusions We have examined the¹³C NMR spectra of para- and meta-substituted alkylthiobenzenes. Steric disruption of the p, -conjugation of sulfur with the aromatic fragment on increase in the size of the alkyl substituents is typical of all the series. The degree of p,-conjugation and the molecular conformation also depend on the electronic effects of the para and meta substituents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1525–1531, July, 1981.     

Synthesis of polymorphicα-(2-benzothiazolyl)-α-phenyl-β-picrylhydrazines and investigation of their properties in the crystalline state and in solutions

Polymorphic modifications of-(2-benzothiazolyl)--phenyl--picrylhydrazine were obtained. The structures of the crystals of the polymorphic modifications were investigated by x-ray diffraction and IR and UV spectroscopy, by a study of the electrical conductivities in nonaqueous media, and by microcalorimetric determination of the heats of solution. It is shown that the physical and chemical properties of the compounds obtained depend on their macromolecular structures in the crystalline state and in solutions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 322–325, March, 1973.     

Study of conjugation effects by means of NMR spectroscopy 21. Factor analysis of NMR parameters of alkyl phenyl ethers and sulfides

Conclusions Increases of effective volume of the alkyl group in the series of alkyl phenyl ethers does not lead to any decrease of -donor properties of the oxygen atom except in the case of the last member of the series investigated, tert-butoxybenzene; in contrast, in the series of alkyl phenyl sulfides, sharp inhibition of conjugation is observed even in isopropylthiobenzene, and in tert-butylthiobenzene, the sulfur atom manifests weak -acceptor properties.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1053–1059, May, 1983.The authors wish to thank V. A. Chertkov for assistance in performing the experiment and discussion of the results that were obtained.     

Some properties of α-(6-methyl-2-benzothiazolyl)α-phenyl-β-picrylhydrazyl, α-(2-methyl- 6-benzothiazolyl)-α-phenyl-β-picrylhydrazyl,and their hydrazines

The structures and properties of -(6-methyl-2-benzothiazolyl)--phenyl--picrylhydrazyl, -(2-methyl-6-benzothiazolyl)--phenyl--picrylhydrazyl, and their corresponding hydrazines nd complexes were studied by means of IR, UV, and visible spectroscopy and electrical conductivity. The half-wave potentials and limiting currents for reduction on a dropping mercury electrode were found for the hydrazines. The charge and spin densities of the investigated compounds were calculated by the Hückel MO and MacLachlan methods. It is shown that in the case of strong interaction with a medium the characteristics of the trinitrophenyl groups of the picrylhydrazines are practically the same, regardless of the structure of the hydrazine residue bonded to them.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 462–467, April, 1971.     

The thermal transformation of an aromatic poly (amide), poly (ortho-oxyamide) and poly (benzoxazole)

The thermal behaviour of three aromatic polymers, poly(3,3-dioxy-4,4-diphenylmethane) (POA), poly(2,2-m-phenylene-5,5-dibenzoxazolemethane) (PBO) and a commercial poly-(phenyleneisophthalamide) (Phenylon) was studied by thermal analysis, i.e. DSC and TG. PBO was formed by the progressive thermocyclization of POA. By transforming POA into PBO the thermal stability was increased proportionally to the degree of cyclization, due to the stiffening of the polymer chain. PBO was found to be more thermally stable than Phenylon. The activation energies of the desorption of moisture, cyclization and thermal degradation of the polymers in both nitrogen and air were determined from non-isothermal TG data.     

Polyformaldehyde as an antifriction material

The antifriction properties of polyformaldehyde have been studied on the velocity interval from 4 · 10^–4 to 10 m/sec and at loads to 300 kgf/cm². Tests were conducted with and without lubrication on laboratory friction machines of various types and under service conditions. Steel, emery cloth, and polyformaldehyde were used as the second member of the friction pair. The values of the coefficients of friction, temperatures and performance limits for polyformaldehyde are compared with those for polycaprolactam.All-Union Scientific Research Institute of Railroad Transport, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 850–856, September–October, 1969.     

Synthesis of reversible carbon dioxide absorber based on hydrated zirconium oxide,intended for concentration and removal of CO<Subscript>2</Subscript> in habitable closed objects

Carbon dioxide absorber based on hydrated zirconium oxide was synthesized with ammonium carbonate and hydrogen peroxide. The effect of the molar ratio between ammonium carbonate and hydrogen peroxide on the sorption characteristics of the absorber was examined. The structural-sorption properties of the absorber were analyzed. It was shown tat the absorber has a high absorption capacity for CO₂.     

Multiple Fourier series for functions from a Zygmund class

The paper considers necessary and sufficient conditions providing that a function of many variables with nonnegative trigonometric Fourier coefficients belongs to the big and small Zygmund classes. Earlier, such results were obtained by R.P. Boas in the one-dimensional case and by V. Fülöp in the two-dimensional case.