Cationic and anionic environments in LiTFSI-doped di-ureasils with application in solid-state electrochromic devices

Fourier Transform mid-infrared and Raman spectroscopies were used to investigate the cation/polymer, cation/urea bridge, cation/anion and hydrogen bonding interactions in poly(oxyethylene) (POE)/siloxane di-ureasil networks prepared by the sol–gel route and doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Materials with compositions 200 ?n ? 5 (where n expresses the molar ratio OCH₂CH₂/Li⁺) were studied. The Li⁺ ions coordinate to the urea carbonyl oxygen atoms over the whole range of salt concentration considered. Bonding to the ether oxygen atoms of the POE chains occurs at n ? 40, although a significant fraction of the POE chains remain non-coordinated. In these high salt content samples, the cations interact with the anions forming contact ion pairs. “Free” ions are probably the main charge carriers at the room temperature conductivity maximum of these ormolytes.     

Synthesis,structure, and phase behavior of carbosilane LC dendrimers with terminal butoxyphenylbenzoate mesogenic groups

Two series of carbosilane LC dendrimers with terminal protonated and deuterated butoxyphenylbenzoate mesogenic groups linked to carbosilane dendritic matrices of the first to fifth generations via an undecylene spacer have been synthesized. The chemical structure of new dendrimers has been studied by ¹H NMR spectroscopy and gel-permeation chromatography. The dendrimers of first-fourth generations are characterized by formation of the smectic C mesophase in a wide temperature range, whereas much more complex columnar supramolecular structures are formed in dendrimers of the fifth generation. Structural studied of mesophases by X-ray diffraction and small-angle neutron scattering show that segregation takes place in mixtures of deuterated and protonated LC dendrimers; as a result, huge aggregates composed of hundreds of chemically unbound molecules develop and the sizes of these aggregates reversibly change with temperature.     

Kinetics and mechanism of formation of isomeric 1-methyl- and 2-methyl-5-vinyltetrazoles

The alkylation of 5-(β-dimethylaminoethyl)tetrazole (1) with dimethyl sulfate afforded 5-(β-dimethylaminoethyl)-1-methyltetrazole (2) and 5-(β-dimethylaminoethyl)-2-methyltetrazole (3). The exhaustive alkylation of compounds 2 and 3 at the terminal dimethylamino group gave 1-methyl-(4) and 2-methyl-5-(β-trimethylammonioethyl)tetrazole (5) methyl sulfates. The proton elimination from the α-methylene (with respect to the tetrazole cycle) groups of the quaternary ammonium cations of salts 4 and 5 by the action of a base leads to the corresponding zwitterions 4 ^± and 5 ^±, which in the rate-determining step undergo the cleavage of the nitrogen—carbon bond with the formation of 1-methyl-5-vinyl- (6) and 2-methyl-5-vinyltetrazole (7). The true constant of the transformation of zwitterion 4 ^± into tetrazole 6 is 21 times higher than that for the transformation of zwitterion 5 ^± into tetrazole 7.     

Kinetics of azidation of isomeric benzenedicarbonitriles

Rate constants and activation parameters of two-step azidation of isomeric dicyanobenzenes with dimethylammonium azide in DMF at 70–100°C were determined. Tetrazole rings are formed from cyano groups in dicyanobenzenes in a stepwise mode following the 1,3-dipolar cycloaddition pattern. The rate of azidation of isomeric dicyanobenzenes is considerably higher than the rate of subsequent azidation of intermediate cyanophenyltetrazolides. The azidation rate constant decrease in going from m-dicyanobenzene to its para and ortho isomers.     

Review of the heats of chemisorption of gases at metals in the context of the problem of ‘Heterogeneous’ <Emphasis Type="Italic">vs.</Emphasis> ‘Homogeneous’ catalytic surfaces

A critical review of available data on the heats of chemisorption of gases at metals is given. The effect of upward technical and procedural trends on measured results is demonstrated. The results for surfaces approached to their states occurring in catalytic processes are accentuated. Several tens of chemisorbent/gas systems are considered; a number of the results are confirmed by several independent measurements. The coverage-independence of heats of chemisorption for powders, supported catalysts, components of multi-component catalysts, and films is demonstrated; the better the techniques and procedures, the closer to zero the angle between the heat-coverage function and the abscissa. The principal conclusion on surface homogeneity of stabilized surfaces is made.     

Methods for the synthesis of mono- and polynuclear NH-tetrazoles. (Review)

Data on methods for the synthesis of monocyclic and polynuclear NH-unsubstituted tetrazoles are reviewed.Dedicated to Prof. H. Elguero on the occasion of his 65th birthday.St. Petersburg State Technological Institute (Technical University), St. Petersburg 198013, Russia; Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 867–884, July, 2000.     

Coking of Catalysts: Mechanisms,Models, and Influence

Kinetics and Catalysis - This review considers the mechanism of multilayered coke formation on catalysts of various types and analyzes its possible variants. A detailed derivation of equations of...     

Tetrachlorosilane–Sodium Azide System in the Synthesis of Tetrazole-Containing D,L-Tryptophane Derivatives

Russian Journal of Organic Chemistry -     

Toward a theory of dual-beam charged-particle acceleration in plasma waveguide

The results of a theoretical study of dual-beam charged-particle acceleration in a plasma waveguide in a string longitudinal magnetic field are presented. It is shown that effective charged-particle acceleration can be realized by using electric-field nonuniformity over the waveguide cross section. It is established that optimal acceleration conditions can be achieved when the particles enter the accelerating field that corresponds to the region of the first amplitude maximu. The maximum electron energy of the accelerated beam is determined as a function of the guiding-beam current. It is established that the current of accelerated electrons that have maximal energy is 5–10% of the total beam current.Khar'kov Physics and Engineering Institute, Academy of Sciences of the Ukrainian SSSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 8, pp. 947–955, August, 1991.