Kinetics and mechanism of nitration of cellulose with the HNO3-CH2Cl2 mixture

Complexing in the HNO₃-CH₂Cl₂ system was confirmed tensimetrically. The kinetics of nitration of wood cellulose by the HNO₃-CH₂Cl₂ mixture were investigated. A large part of the cellulose is nitrated in a first fast reaction in comparison to the HNO₃-H₂SO₄ mixture with the same concentration of HNO₃. The rate of the process is determined by the rate of diffusion of the HNO₃, the rate of the process decreases more rapidly in the case of HNO₃-CH₂Cl₂ than in the HNO₃-H₂SO₄ mixture, which is probably due to the effect of CH₂Cl₂ on the diffusion coefficient of HNO₃.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2445–2450, November, 1989.     

Isostructural self-assembled monolayers. 2. Methyl 1-(3-mercaptopropyl)-oligo(ethylene oxide)s

The structural order and ordering conditions of the self-assembled monolayers (SAMs) of HSCH2CH2CH2O(EO)xCH3, where EO = CH2CH2O and x = 3-9, on polycrystalline gold (Au) were determined by reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and electrochemical impedance spectroscopy. For x = 5-7, RAIRS and SE data show that the oligo(ethylene oxide) [OEO] segments adopt the near single phase, 7/2 helical conformation of the folded-chain crystal polymorph of crystalline poly(ethylene oxide), oriented normal to the substrate. These SAMs exhibit OEO segment structure and orientation identical to that found in a previous isostructural series [HS(CH2CH2O)6-8C18H37 SAMs. Vanderah, D. J., et al. Langmuir 2003, 19, 3752] and are anisotropic films for surface science metrology where structure is constant and thickness increases in 0.30 nm increments. In addition, this is the first example of OEO SAMs to attain this highly ordered, helical conformation where the (EO)x segment is separated from the Au-sulfur headgroup by a polymethylene chain. For x = 4, 8, and 9, the SAMs are largely helical but show evidence of nonhelical conformations and establish the upper and lower limits of the isostructural set. For x = 3, the SAMs are largely disordered containing some all-trans conformation. SAM order as a function of immersion time from 100% water and 95% ethanol indicates that the HSCH2CH2CH2O(EO)5-7CH3 SAMs order faster and under a wider range of conditions than omega-alkyl 1-thiaolio(ethylene oxide) [HS(EO)xCH3] SAMs, reported earlier (Vanderah, D. J., et al. Langmuir 2002, 18, 4674 and Vanderah, D. J., et al. Langmuir 2003, 19, 2612).     

Synthesis and stereoisomerism of N-oxides of the decahydroquinoline series

The results of the oxidation of a number of 4-substituted 1,2-dimethyldecahydro-4-quinolones with hydrogen peroxide in methanol are in conformity with the results obtained by us earlier and confirm that the stereochemistry of the oxidation of nitrogen depends on the configuration of the methyl substituent in the 2 position of the decahydroquinoline ring. Under these conditions, the epimeric 1,2-dimethyl-trans-decahydro-4-quinolones undergo partial interisomerization at the 2 position to give a mixture of three N-oxides that correspond to both amino ketones. The oxidation of the corresponding ketals proceeds like the oxidation of amino alcohols without epimerization. It is thereby shown that the epimerization of the C₂ center during the formation of the N-oxides from epimeric 1,2-dimethyl-trans-decahydro-4-quinolones occurs with the participation of the carbonyl group.     

Diagnostics of the Phase Composition of Lead-Zirconate-Titanate Films according to Raman Spectra: Phase Identification

The problem concerning the diagnostics of the phase composition of lead-zirconate-titanate (PZT) films under conditions of overlapping Raman spectra is solved via applied mathematical statistics. The proposed phase-identification method based on reference spectra is implemented using different Raman-spectrum regions measured on the surface of multiphase PZT films. It is demonstrated that the identification of phases, as well as determination of their concentration, must be performed using the spectral range in which the calculated first principal components of the set of Raman spectra differ to the greatest extent from each other.     

Furanose Bicyclophosphites as Synthons of Modified Nucleoside Diphosphates

Abstract

Previously we synthesized and examined in detail 1,2- alkylideneglucofuanose 3,5,6-bicyclophosphites; mono- and bicyclophosphates with peculiar chemical and physiological activity were obtained on their base [1]. During the study of their structural dependence, we modified the hydrocarbonic moiety, synthesiz-ed 1,2,3- and 3,5,6-bicyclophosphites and cyclophosphates of gulofuanose, and correlated their features with those of glucose analogues. Furthermore, an additional phosphonate moiety (obtained by a stereoselective reaction of an appropriate ketonic sugar with silylphosphites) was introduced into the glucofuranose 3,5,6-bicyclophosphite molecule to the third carbon atom. As a result, the monosaccharide matrix gained two functional groups containing tri- and fourcoordinated phosphorus.     

Synthesis of 5,10,15,20-tetra[6' -nitro-1,3,3-trimethylspiro- (indolino-2,2' -2H-chromen-5-yl)]porphyrin and its metal complexes

A new 5,10,15,20-tetrasubstituted porphyrin containing four 6’-nitro-1,3,3-trimethylspiro(indolino-2,2’-2H-chromene) substituents and its complexes with Zn²⁺ and Cu²⁺ ions were prepared and characterized by physicochemical methods of analysis.     

Estimation of ion scattering by atomic chains on single crystal surfaces

Estimation of ion movement close to atomic chains taking into account the elastic and inelastic energy losses and vacancy type imperfections was performed on the basis of a model of binary interactions of ions with the atoms of a crystal.

An analysis of results shows that at scattering by atomic chains a phenomenon which makes a substantial contribution to scattering by the single crystal surface the inelastic energy losses exceed the single scattering ones by a factor of 5–6.