Photochemical and thermal transformations of azomethine imines

The thermal and photochemical fragmentations of a few bisazoalkenes have been investigated. 2-Phenyl-4,5-disubstituted-1, 2,3-triazoles were obtained both in the thermolysis and photolysis of 1, 2-bisphenylazo-(4, 4′-dichloro) stilbene, 1, 2-bisphenylazo(4, 4′-dimethoxy)stilbene, 1, 2-bisphenylazocyclohexene and o-(phenylazo) phenyldiazocyanide. Both 2, 3-bisphenylazo-2-butene and 1, 2-bisphenylazoethylene failed to undergo either photolysis or thermolysis in the expected manner. However, 2, 3-bisphenylazo-2-butene underwent an acid-catalysed valence isomerisation to anhydro 1-phenylimino-2-phenyl-4, 5-dimethyl-1, 2, 3-trizolium hydroxide, which on photolysis gave 2-phenyl-4, 5-dimethyl-1, 2, 3-triazole. The same iminotriazolium intermediate gave a cycloadduct, 2, 6-diphenyl-3, 3a-dimethyl-4, 5-dicarbomethoxypyrazolino [2.3.c][1.2.3] triazole, on treatment with dimethyl acetylenedicarboxylate, whereas treatment with carbon disulphide gave 2-phenyl-4, 5-dimethyl-1, 2, 3-triazole. Both photolysis and thermolysis of C-biphenylene-N^α(4-chlorophenyl)-N^β-cyanoazomethine imine gave 9-fluorenone-N- (4-chlorophenyl) anil. Photolysis of 1, 2-bisphenylazoacenaphthylene in methanol gave acenaphthenequinone monophenylhydrazone.     

Zinc and cadmium complexes based on 3,6-di-tert-butyl-o-benzoquinone

Zinc and cadmium bis-o-semuquinolate and catecholate complexes are synthesized by the reduction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with amalgamated metals in a medium of various solvents. The oxidation of the metal catecholate derivatives results in the corresponding mono-o-semiquinone complexes, which undergo symmetrization to form the metal bis-o-semiquinolates. The molecular structures of the complexes (3,6-SQ)₂Zn · Py, (3,6-SQ)₂Zn · H₂O, and (3,6-SQ)₂Cd · α,α′-Bipy (3,6-SQ is the radical anion of 3,6-Q) are studied by X-ray diffraction analysis. Magnetochemical studies are carried out for the zinc and cadmium bis-o-semiquinone complexes.     

Catalytic and thermal transformations of methyl- and isopropylcyclobutanes

Conclusions The thermal decomposition of the methyl- and isopropylcyclobutanes in the presence of quartz powder proceeds only with cleavage of the ring at two bonds, while in the presence of amorphous aluminosilicate and zeolite NM the additional reactions of ring opening, cleavage of groups containing one carbon atom, and hydrogen redistribution take place.Translated from Izvestya Akademii Nauk SSSR, Seriya Khimieheskaya, No. 1, pp. 170–172, January, 1973.     

Exfoliation and thermal transformations of Nb-substituted layered titanates

Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating, the thermal transformation into anatase and further to rutile is retarded. This suppression of the phase transition upon higher valent substitution may promote technological applications of anatase thin films, hereunder development of films with TCO properties. Depending on the oxygen partial pressure during the transformation, the Nb-substitution into TiO₂ provokes different defect situations and also electronic properties. At reducing conditions, Nb is incorporated as Nb^V and an equivalent amount of Ti^IV is transformed to Ti^III as evidenced by XPS. Magnetic susceptibility data show accordingly paramagnetic behavior. For samples heated in air Ti^IV and Nb^V cations prevail, the latter is compensated by cation vacancies. ⁹³Nb MAS NMR data prove that Nb is finely dispersed into the transformed (Ti,Nb)O₂ oxide matrices without sign of Nb₂O₅ (nano)precipitates. The Nb-O-Ti bonds and defects at cation sites are considered key factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates are appropriate precursors for formation of highly oriented Nb-substituted anatase thin films via delamination, reconstruction and subsequent heat treatment.     

Study of thermal transformations of aluminum phosphate binder and composites on its basis with various fillers

Results are reported obtained in a study of the physicochemical processes occurring under heating in the temperature range 150–1100°C of an aluminum phosphate binder and composites on its basis with various fillers (SiO₂, Al₂O₃, BN, and TiO₂ nanoparticles) with the use of an X-ray diffraction analysis.     

Classification of physico-chemical transformations in thermal analysis

In the present classification the different types of physicochemical transformations are dealt with which may be useful in studying different substances by the methods of thermal analysis. Equations were derived for describing the correlation between the thermodynamic characteristics and the parameters of the differential thermal analytical (DTA) peaks for two classes of physicochemical transformations.All experiments were conducted on DTA-4 instruments constructed in the Baykov Institute of Metallurgy, the USSR Academy of Sciences.

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Synthesis and thermal transformations of spiro-fused N-phthalimidoaziridines

Oxidation of N-aminophthalimide in the presence of 2-arylideneinden-1,3-diones with electron-withdrawing substituents gives the corresponding 3-aryl-1-phthalimidospiro[aziridine-2,2′-indene]-1′,3′-diones in good yields. Heating these aziridines with standard dipolarophiles (N-phenylmaleimide, dimethyl acetylenedicarboxylate, maleate, and fumarate) leads, in most cases, to spiro[inden-2,2′-pyrrole] derivatives as products of 1,3-dipolar cycloaddition of the intermediate azomethine ylides with up to 70–95% yields in the case of N-phenylmaleimide. As is typical for 2-acylaziridines, the competing rearrangement into 2-aryl-4H-indeno[2,1-d][1,3]oxazol-4-ones prevails for less active dipolarophiles. Increasing the electron-releasing properties of the 3-aryl ring allows the observation of the push–pull effect of electron-donating and electron-withdrawing substituents on the ease of the three-membered ring-opening.     

Phase transformations and thermal recrystallization of hydrated cobalt molybdate

Journal of Thermal Analysis and Calorimetry - The thermal evolution of a very fine-grained hydrated cobalt molybdate, CoMoO4 · · 0.9H2O, has been studied by dilatometry, DTA, X-ray...     

Curved graphite and its mathematical transformations

Mathematical transformations for graphite with positive, negative and zero Gaussian curvatures are presented. When the Gaussian curvatureK is zero, we analyse a bending transformation from a planar sheet into a cone. The Bonnet, the Goursat and a mixed transformation are studied for graphitic structures with the same topologies as triply periodic minimal surfaces (K < 0). We have found that using the Kenmotsu equations for surfaces of constant mean curvature it is possible to invert spherical and cylindrical graphite. A bending transformation for surfaces of revolution is also studied; during this transformation the helical arrangement of cylinders changes. All these transformations can give an insight into kinematic processes of curved graphite and into new shapes.     

Kinetics of thermal transformations in nanosized chromium films

The transformations in nanosized chromium layers at different layer thicknesses (d = 14–154 nm) and thermal treatment temperatures (T = 673–873 K) were studied by optical spectroscopy, microscopy, and gravimetry. The kinetic curves of conversion at different chromium film thicknesses and treatment temperatures are well approximated by the linear, inverse logarithmic, cubic, and logarithmic functions. The contact potential difference for Cr and Cr₂O₃ films and photo-emf for Cr-Cr₂O₃ systems were measured. An energy band diagram of Cr-Cr₂O₃ systems was constructed. A model of thermal transformation was constructed for Cr films that included the stages of oxygen adsorption, charge carrier redistribution in the contact field of Cr-Cr₂O₃, and chromium(III) oxide formation.     

Kinetic laws of thermal transformations in nickel nanofilms

Transformations in nickel nanofilms as a function of thickness (d = 3–60 nm) and temperature of heat treatment (T = 373–873 K) are studied via optical spectroscopy, microscopy, and gravimetry. It is found that, depending on the thickness of nickel films and temperature of heat treatment, the kinetic curves of the degree of transformation are satisfactorily described in terms of the linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference for Ni and NiO films and the photovoltage for Ni-NiO systems are measured. An energy band diagram for Ni-NiO systems is constructed. A model of the thermal transformation of Ni films, including the stages of oxygen adsorption, charge carrier redistribution in a Ni-NiO contact field, and the formation of nickel(II) oxide, is proposed.     

Potassium polytitanates intercalated with nickel ions and their thermal transformations

The intercalation of nickel ions into the layered structure of ultradispersed amorphous potassium polytitanate powder on treatment with an aqueous solution of nickel sulfate was studied. The limiting nickel content that can be attained by intercalation is 12.8 wt %. The nickel ion intercalation results in a decrease in the average particle size of potassium polytitanate and in the structural ordering. Heat treatment of the resulting intercalate promotes the formation of a nanocomposite consisting of the solid solution K_1.35(Ni _x Ti_{8 − x} )O₁₆ with the hollandite structure, Ti₂O₃, and, depending on the treatment schedule, either NiO nanocrystals or Ni metal.     

Synthesis and thermal transformations of 5-nitropyrimidin-4-yl dialkyldithiocarbamates

On heating, 5-nitropyrimidin-4-yl dialkyldithiocarbamates undergo two types of transformations. One type of these transformations involves intramolecular ipso-substitution of the nitro group to form bis(4-dialkylcarbamoylthiopyrimidin-5-yl) disulfides, whereas another type of transformations involves elimination of carbon disulfide to give 4,6-diamino-5-nitropyrimidine derivatives. The reaction pathway is controlled by the steric effect of the substituent at position 6 of the pyrimidine ring.     

Zinc and cadmium dihydroxide molecules: matrix infrared spectra and theoretical calculations

Laser-ablated zinc and cadmium atoms were mixed uniformly with H2 and O2 in excess argon or neon and with O2 in pure hydrogen or deuterium during deposition at 8 or 4 K. UV irradiation excites metal atoms to insert into O2 producing OMO molecules (M = Zn, Cd), which react further with H2 to give the metal hydroxides M(OH)2 and HMOH. The M(OH)2 molecules were identified through O-H and M-O stretching modes with appropriate HD, D2, (16,18)O2, and (18)O2 isotopic shifts. The HMOH molecules were characterized by O-H, M-H, and M-O stretching modes and an M-O-H bending mode, which were particularly strong in pure H2/D2. Analogous Zn and Cd atom reactions with H2O2 in excess argon produced the same M(OH)2 absorptions. Density functional theory and MP2 calculations reproduce the IR spectra of these molecules. The bonding of Group 12 metal dihydroxides and comparison to Group 2 dihydroxides are discussed. Although the Group 12 dihydroxide O-H stretching frequencies are lower, calculated charges show that the Group 2 dihydroxide molecules are more ionic.     

Investigation of thermal transformations of propylene and its role in the formation of benzene by pyrolysis of n-hexane

Conclusions We investigated the thermal transformations of propylene and mixtures of n-hexane and propylene at 800C by use of radioactive hydrocarbons labeled with¹⁴C. The data obtained lead to the conclusion that on pyrolysis of n-hexane benzene is formed by the interaction of propylene with 1,3-butadiene or by intermediate formation of 1,3-butadiene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1556–1560, July, 1984.