Radiation degradation of copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate

Copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate (OM) were investigated as deep-UV and e-beam resists. Their increased sensitivity relative to PMMA (up to 50 times) was correlated with the radiation chemical yields of the volatile products and main chain scissions. The degradation of these copolymers, activated by the 3-oximino-2-butanone entity, is discussed in terms of energy absorption mechanisms and the subsequent scission reactions.     

Ring closure of some O-aryl ethers of ketoximes to benzofurans

The action of alcohol solutions of hydrogen chloride on aryl ethers of the oximes of N-substituted 4-piperidones (Ia-c) yielded rearrangement products — 3-(2-hydroxyaryl)-4-piperidones (IIa, b) and (or) 4a-aikoxy-l,2,3,4,4a,9b-hexahydrobenzofuro[3,2-c]pyridines (IIIa-c), which, under certain conditions, are readily converted to 1,2,3,4-tetrahydrobenzofuro[3,2-c]pyridines (IVa, b). Ketones of the II type are ketalized to dihydrobenzofurans III by alcohol solutions of hydrogen chloride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1596–1600, December, 1971.     

Simplified high-performance liquid chromatographic determination of residual amprolium in edible chicken tissues

A simplified determining method for the routine monitoring of residual amprolium in edible chicken tissues (muscle and liver) is developed using a high-performance liquid chromatographic (HPLC) method with a photodiode-array detector after sample cleanup by an Ultrafree-MC/PL centrifugal ultrafiltration unit. For the HPLC determination and identification, a Mightysil RP4 GP column and a mobile phase of an ethanol-5 mM 1-heptanesulfonic acid sodium salt solution (35:65, v/v) using an ion-pairing system with a photodiode-array detector are used. Average recoveries (spiked at 0.3-3.0 microg/g) are > 90%. The inter- and intravariabilities are 1.9-2.4%. The limits of quantitation are 0.22 microg/g for muscle and 0.25 microg/g for liver. The total time and solvent required for the analysis of one sample are < 20 min and < 2 mL of ethanol, respectively. No toxic solvents and regents are used.     

Displacement of metal atoms from salts by hydrogen and the role of this reaction in chain processes

The interaction of hydrogen atoms with a variety of alkali metal and alkaline-earth metal salts results not only in the recombination of these atoms but also in the displacement, into the gas phase, of free radicals (CaCl^·(A ¹ P _1/2, B ² S ⁺) and CaF^·(A ² P)) and metal atoms, including their excited species, which are detected spectroscopically. Transmission spectra indicate that the NaCl surface undergoes metallization when treated with a high-frequency discharge and a rarefied hydrogen flame. Combustion is affected by the gas-phase hydrogen atoms involved in the chain reaction and by the varying composition and properties of the surface. The concentration of Na atoms over the NaCl surface at 770 K is 10⁹?10¹¹ cm^?3 in a stream of H atoms at 1 Torr and in the 2H₂ + O₂ flame at 4 Torr. The concentration of sodium atoms in the ² P _3/2 and ² P _1/2 excited states is ～5 × 10⁶?5 × 10⁸ cm^?3. The role of the discovered reactions in combustion, pyrolysis, and plasma chemistry is discussed.     

Setting the boundary conditions by the potential shift in the self-consistent field (Xα-scattered wave) cluster calculations

Potential shifts given by the Madelung potentials in different regions of a molecular cluster are determined in the MT approximation. Nickel and zinc oxides are employed to consider the interrelation between the approaches to the calculation of the boundary conditions in terms of the Watson sphere and the potential shift in the cluster calculations of perfect and imperfect ionic crystals using the self-consistent field (Xα-scattered wave) method. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 1, pp. 23–31, January–February, 1997. Original article submitted February 12, 1996.     

Spectral-luminescent analysis of sugar cane juice

A spectral-luminescent analysis has been made of the low-, medium-, and high-molecular mass fractions of sugar cane juice. The presence of pigments was detected in all the fractions. The medium-molecular-mass fraction was distinguished by the most considerable and most diverse composition of the pigments, a substantial contribution to which was made by the products of the alkaline decomposition of sugars. The amounts of pigments in all the fractions of the juice depended on the age of the plant. A pronounced dependence on the age of the plant was characteristic for the medium-molecular-mass fraction.B. I. Stepanov Institute of Physics, Belorussian Academy of Sciences, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 456–459, May–June, 1993.     

NMR spectroscopy of metal cyclopentadienyls VIII. Prototropism and dimerisations of silicon cyclopentadienyls

Studies have been made of the slow dynamic processes which occur with the silicon cyclopentadienyls C₅H₅Si(CH₃)Cl₂, such as prototropic rearrangement and dimerisation. The product formed through spontaneous dimerisation has been found to consist almost entirely of the dimer of the main vinylic isomer of C₅H₅Si(CH₃)Cl₂. The dimeric structure has been proved by means of PMR spectra (100 MHz). From kinetic studies values of the rate constants at temperatures of 20,44,55, and 65° have been obtained and an approximate plot of log kvs. (1/T)x10³, has enabled the thermodynamic characteristics of the prototropic rearrangement and of the dimerisation to be calculated. The ability of cyclopentadienyl systems to undergo hydrogen migration is discussed and the reactivity of fluxional systems is shown to be governed by the rate of metallotropic rearrangement.     

Oxidation of the [Rh(CO)2Cl2] anion in aqueous solution

The reaction of rhodium(I) carbonyl chloride, [Rh(CO)₂Cl]₂, with dichromate, cerium(IV) sulfate, hexachloroplatinic acid or p-benzoquinone in aqueous hydrochloric acid proceeds by consumption of 4 equivalents of oxidizing agent per mole or rhodium(I) in accordance with the equation Rh^I(CO)₂  4e + H₂O → Rh^III(CO) + 2H⁺ + CO₂A “cyclic” oxidation mechanism is suggested.     

Hydrogenation without a transition-metal catalyst: on the mechanism of the base-catalyzed hydrogenation of ketones

The hydrogenation of unsaturated organic substrates such as olefins and ketones is usually effected by homogeneous or heterogeneous transition-metal catalysts. On the other hand, a single case of a transition-metal-free and purely base-catalyzed hydrogenation of ketones was reported by Walling and Bollyky some 40 years ago. Unfortunately, the harsh reaction conditions (ca. 200 degrees C, >100 bar H(2), potassium tert-butoxide as base) limit the substrate spectrum of this reaction to robust, nonenolizable ketones such as benzophenone. We herein present a mechanistic study of this process as a basis for future rational improvement. The base-catalyzed hydrogenation of ketones was found to be irreversible, and it shows first-order kinetics with respect to the substrate ketone, hydrogen, and catalytic base. The rate of the reaction depends on the type of alkali ion present (Cs > Rb - K > Na > Li). Using D(2) instead of H(2) revealed a rapid base-catalyzed isotope exchange/equilibration between the gas phase and the solvent as a concomitant reaction. The degree of deuteration of the product alcohols did not indicate a significant kinetic isotope effect. It is proposed that both ketone reduction and isotope exchange proceed via similar six-membered cyclic transition states involving the H(2)(D(2))-molecule, the alkoxide base, and the ketone (solvent alcohol in the case of isotope exchange). Mechanistic analogies are pointed out which apparently exist between the base-catalyzed hydrogenation of ketones studied here and the Ru-catalyzed asymmetric ketone hydrogenation developed by Noyori. In both cases, heterolysis of the hydrogen molecule appears to be assisted by a Br?nsted-base (i.e., alkoxide), the latter being bound to the substrate ketone or the catalyst ligand, respectively, by a bridging Lewis-acidic alkali ion.     

Preparation of isomeric 1,3- and 1,5- (o-phenylene)-hexamethylcyclotetrasiloxanes and investigation of their spectral characteristics

Workup of the mixture of products of pyrolysis of cyclotetrasiloxane (Me₂SiO)₂(MePhSiO)₂ yielded 1,3- (I) and 1,5-(o-phenylene)cyclosiloxane (II), the structures of which were established on the basis of data from their IR, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 24–25, January, 1978.