Quantum-chemical simulation of the adsorption and catalytic processes in a pore of the NaX-type zeolite

In terms of density functional theory, we perform quantum-chemical calculations of variations in the energetic and structural characteristics of methanol, benzene, and propane molecules as they are adsorbed in a pore of the NaX-type zeolite and on a fragment of its cavity. The position of benzene, alcohol, or propane molecules near the Na cation is the most energetically favorable; in addition, the alcohol molecule forms a hydrogen bond with the oxygen bridge of the zeolite. If two alcohol molecules are adsorbed, they also are localized near the Na cation and form an intermolecular hydrogen bond. A comparative simulation of the catalysis of the propane dehydration reaction in a cavity of NaX-type zeolite and on its fragment is performed; the effect of the steric factors on the simulation results is analyzed.     

Comparison of nitrotyrosine antibodies and development of immunoassays for the detection of nitrated proteins

Three monoclonal antibodies (mAb) and three polyclonal antibodies (pAb) have been characterized and compared with respect to their cross-reactivities and affinities for 3-nitrotyrosine, eight aromatic compounds with similar chemical structures, a peptide containing a single nitrotyrosine residue, and fourteen nitrated protein standards (bovine serum albumin, BSA) containing different numbers of nitrotyrosine residues per protein molecule (0.2 to 16.8). In indirect competitive immunoassays, mAb Alexis 39B6 exhibited the highest affinity for free 3-nitrotyrosine (10(6) L mol(-1)), while the pAb Oxis 24312 from sheep exhibited the highest affinities for nitrated proteins (up to 10(8) L mol(-1)). The apparent affinities determined in the indirect competitive assays were inversely correlated with the limits of detection (LOD) determined in one-sided immunoassays. With the sheep pAb minimum LOD on the order of 10 pmol L(-1) were achieved for highly nitrated proteins, corresponding to effective LOD on the order of 100 pmol L(-1) for nitrotyrosine residues. In the one-sided assays, however, the LOD for nitrated proteins increased proportionally with increasing background concentrations of native proteins in the investigated samples. Sandwich immunoassays combining pAb and mAb for selective enrichment and detection of nitrated proteins allowed to eliminate this native protein matrix effect and to achieve LOD on the order of 300 pmol L(-1) for highly nitrated proteins independent of native protein background concentrations.     

Structure and spectroluminescence properties of derivatives of 1,8-naphthoylene-1',2-benzimidazole with substituents of various electronic types

A series of quantum-chemical calculations using the CNO SCF CI method were carried out to account for the nontraditional influence of substituents of various electronic types on the spectroluminescence characteristics of naphthoylenebenzimidazole. It is shown that the principal direction of electron-density redistribution during excitation of this molecule is the charge transfer from its benzene fragment to its naphthalene fragment, and the most appreciable change in spectrofluorescence characteristics compared to the unsubstituted compound is achieved by introducing electron-donor substituents into the benzimidazole fragment, and in electronacceptor characteristics, into the naphthalene fragment of the naphthoylenebenzimidazole molecule.Institute of Single-Crystals, National Academy of Sciences of Ukraine, Khar'kov 310001 and Khar'kov State University, Khar'kov 310077. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 633-639, May, 1995. Original article submitted Anril 10. 1995.     

Entropy/information bond indices of molecular fragments

The communication channels of the disconnected (mutually non-bonded, closed) parts of the molecule are investigated. The entropy/information indices of such subsystems are proposed as measures of the intra-fragment (internal) information bond-order and its covalent/ionic components. The molecular fragment bond-order conservation and a competition between its ionic and covalent contributions are examined. An approximate scheme in the spirit of the grouping theorem of the Information Theory (IT), for combining the subsystem entropy/information data into the corresponding global quantities describing the system as a whole, is derived and tested. It uses the independent subsystem approximation to estimate the entropy/information indices of the inter-fragment (external) chemical interactions in the molecule. The applications to simple orbital models, including the three-orbital model of the transition state complex and the π bond systems (butadiene and benzene) in the Hückel theory approximation, are used to illustrate the concepts proposed.     

Mass-spectrometric behavior of benzo-substituted dibenzo-18-crown-6 ethers

It was shown that the intensity of the peak of the molecular ion in the mass spectra of dibenzo-18-crown-6 derivatives depends to a marked extent on the electronic properties of the substituents on the benzene ring. Fragmentation of the substituents is observed after the decomposition of the polyether ring. This permits the proposition that the preferred localization of the charge in the molecular ion and the fragment ions is on the oxygen-containing part of the molecule. The analysis of the mass spectra of benzo-substituted crown ethers renders possible the determination of substituents occurring in the aromatic part of the molecule and their steric position.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 783–786, June, 1986.     

Studies of 4H-3,1-benzoxazines

Bromination of 2,4-substituted 1,2-dihydro-4H-benzoxazines with bromine in acetic acid was conducted. It was shown that either the corresponding 6,8-dibromo-1,2-hydrobenzoxazines or the products of their dehydrogenation — 6,8-dibromobenzoxazines, are primarily formed as a function of the structure of the dihydrobenzoxazine and the concentration of bromine in the reaction mixture. The structure of 6,8-dibromo-2-(5-nitrofuryl-2)-4, 4-diphenyl-1,2-dihydro-4H-3,1-benzoxazine was investigated by XSA. A stacking interaction between the nitrofuran fragment of one molecule and the condensed benzene ring of the other was detected in the crystal.See [1] for Communication 12.Kuban State Technological University, Krasnodar 350072. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1391–1397, October, 1997.     

Analysis of the hyperfine structure of the EPR spectrum of the radical ions of aryl- and diaryldiazocyanides

EPR and quantum chemical methods have been used to establish the nature of the distribution of spin density in electrochemically generated radical anions of diaryldiazocyanides. For the symmetrical diphenyldiazocyanides the unshared electron is distributed over the entire molecule, whereas the introduction of a bridge between the benzene rings leads to the localization of the unshared electron only on one fragment of the molecule.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. M. V. Lomonosov Moscow State University, 119899 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1552–1556, July, 1992.     

Nucleophilic Addition of Secondary Amines to Bis[2-(5-trimethylsilyl-(germyl))thienyl]dimethylsilane(germane)-1,1,1′,1′-tetroxides

Lithiation of 2-trimethylsilyl- and 2-trimethylgermylthiophenes by n -BuLi and subsequent silylation or germylation by dichlorodimethylsilane or dichlorodimethylgermane give bis[2-(5-trimethylsilyl-(germyl)thienyl]dimethylsilanes and -germanes ( 1a-d ). Their oxidation with 4 equivalents of m -chloroperbenzoic acid leads to formation of corresponding thiophene-1,1,1'1'-tetroxides ( 2a-d ). Nucleophilic addition of secondary amines to thiophene-1,1,1'1'-tetroxides ( 2a-d ) has been studied. It has been shown that the basicity of amine and the nature of solvent determine the reaction pathway. In water, the addition of two dimethylamine or piperidine molecules and only one diethylamine or morpholine molecule to each thiophene-1,1,1'1'- tetroxide fragment of the sulfone was accompanied by complete desilylation and degermylation. In organic solvents (benzene, THF) the addition of two piperidine molecules to each thiophen-1,1-dioxide fragment of bis[2-(5-trimethylsilyl)thienyl]dimethylsilane was observed. In this case the desilylation of both trimethylsilyl and dimethylsilyl groups occurred.     

Enzyme immunoassays for the investigation of protein nitration by air pollutants

Two enzyme immunoassays have been developed, characterised, and applied to investigate protein nitration in birch pollen extract (BPE) and bovine serum albumin (BSA) samples exposed to air pollutants. The monoclonal antibody CAY-189542 against nitrotyrosine (raised against peroxynitrite-treated keyhole limpet hemocyanine) was characterised in an indirect competitive assay (affinity and cross-reactivities) and applied in a new one-sided enzyme immunoassay for nitrated proteins. The one-sided assay was calibrated against a nitrated BSA standard with an average of 14 nitrotyrosine residues per molecule (nitro-(14)-BSA; detection limit 8.3 pmol L(-1)), and the sensitivity of the test was found to be significantly enhanced by a multivalent binding mode of the monoclonal antibody (bonus effect of multivalency). The same antibody and a polyclonal antibody against Bet v 1, the most prominent birch pollen allergen, were used in a new sandwich immunoassay for specific determination of nitrated Bet v 1. This assay was calibrated against a nitrated Bet v 1 standard with an average of 3 nitrotyrosine residues per molecule (nitro-(3)-Bet v 1; detection limit 0.2 nmol L(-1)). Bet v 1 and BSA exposed to polluted urban outdoor air and to synthetic gas mixtures containing NO2 and O3 at atmospherically relevant concentration levels were found to be efficiently nitrated within hours to days. Pronounced correlations of nitro-(14)-BSA equivalent concentrations with exposure time and with nitro-(3)-Bet v 1 equivalent concentrations in nitrated BPE samples were observed. Test experiments indicated that the efficiency of protein nitration was strongly enhanced by reactive species formed upon interaction of NO2 with O3 and H2O (e.g. NO3 and HNO3). Potential implications of protein nitration by air pollutants are outlined and discussed.     

Bromination and nitration of 2 (3) - ph enyl-5(6)-hydroxybenzofurans

It was established that substituents primarily are incorporated in the benzene ring in the bromination and nitration of 2(3)-phenyl-5(6)-hydroxybenzofurans. The acetoxy derivatives of the same benzofurans are brominated and nitrated only in the free position of the furan ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 311–315, March, 1976.     

Surface induced reactions of cluster ions

First results are presented from a new apparatus, consisting of a supersonic beam for generating neutral clusters, a variable energy electron gun for ionizing the clusters, and a tandem mass spectrometer set-up for studying surface induced reactions of mass and energy selected cluster ions. Rare gas cluster ions, fragment ions from SF₆, benzene ions and benzene cluster ions have been investigated so far. Cluster ion dissociation, intracluster ion molecule reactions and surface reactions with adsorbed hydrocarbons have been shown to be important reaction channels for these ion-surface collision at energies ranging from a few eV to 500 eV. The surface induced fragmentation spectrum is demonstrated to be a useful tool for probing binding energy and structure of cluster ions.     

酞菁分子XPS的CNDO研究

基于在生理、催化等方面研究中的重要作用,H_2Pc分子的电子结构一直受到广泛的注意和研究。但是,理论上算出的电荷分布与实验上测出的NIS XPS信息,目前还不相符。为此,本文用CNDO/2计算方法,对应H_2Pc的文献几何构型,进一步考察了H_2Pc与H_2Pc＇的电子结构。计算方法和结果H_2Pc和H_2Pc＇的骨架构型见图1。对于固态与气态的H_2Pc,目前多数人认为其具有D_(2h)点群对称性(尽管作为D_(4h)点群对称性的根据也是存在的)。为考察分子构型改变(特别是切割)对分子的电子结构、特别是电荷分布的影响,我们     

Molecular structure of N-mesityl-6H-anthra[9,1-bc]pyrrol-6-one

The molecular and crystalline structure of 1-(2,4,6-trimethylphenyl)-6H-anthra-[9,1-bc]pyrrol-6-one was determined by the x-ray structural method. There is a larger uniformity of the bonds in the benzene ring of the isoindole fragment than in the N-substituted isoindoles; this derives from the electronic influence of the keto group. The structure of the whole molecule does not have marked 1,10-anthraquinoid character.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 485–490, April, 1988.     

Synthesis of Nitroanilines Catalyzed by Horseradish Peroxidase in the Presence of NaNO2 and H2O2

The synthesis of nitroanilines catalyzed by horseradish peroxidase（HRP） in the presence of sodium nitrite and hydrogen peroxide was investigated, o-Nitroaniline and p-nitroaniline were found in the nitrated products. 2-Aminotoluene and 4-aminotoluene could also be nitrated to give corresponding nitrated products. This protocol has great potentials to open new avenues useful for the synthesis of nitroaniline and its derivatives.     

Properties of liquid crystal molecules from first principles computer simulation

We explore the valence charge distribution, equilibrium geometry and harmonic force fields of the 4-pentyl-4-cyanobiphenyl (5CB) molecule and the benzene (C6H6) molecule, which provides an important mesogenic fragment, using first principles techniques adapted from large scale electronic structure calculations of periodic solids. We present for the first time accurate structural data for the isolated 5CB molecule and observe subtle broken symmetries relative to the constituent mesogenic fragments. The dynamic properties of these molecules are determined by diagonalization of dynamical matrices, the elements of which are obtained directly from quantum mechanical Hellmann-Feynman forces. Results for both molecules are in excellent agreement with available spectroscopic data, and for benzene are comparable to the most accurate quantum chemistry calculations to date. For 5CB we also present values for the molecular dipole and quadrupole moments.     

Pressurization studies in a sealed autoclave for thermal decomposition of nitrated TBP and TiAP

Study of runaway reaction between tri-n-butyl phosphate (TBP) and nitric acid resulting in red-oil formation (and related problems) in the process evaporators of reprocessing plants has been a major safety concern since last 50 years. Thermal decomposition of nitrated TBP results in rapid pressurization and in close-vent condition it may lead to failure of process vessel and containment. Thermal decomposition of nitrated TBP is reported in the literature but corresponding studies for alternate PUREX/UREX solvent tri-iso-amyl phosphate (TiAP) are not available. In this work, comparative study of the thermal decomposition of nitrated solvents (TBP as well as TiAP) under adiabatic conditions in a sealed autoclave is presented. Experimental results indicate much lesser pressurization in the case of TiAP as compared to TBP.     

Bromination of spiropyrans and reduction of their nitro derivatives

Depending on the nature of the nitrogen heteroring, either substitution only in the chromene ring (phenanthridine derivatives) or in both fragments of the molecule (indoline derivatives) occurs in the bromination of spiropyrans of the phenanthridine and indoline series with N-bromosuccinimide in low-polarity solvents, in which they are found in the cyclic form. The activity of the chromene fragment in both types of spiropyrans is approximately the same. The corresponding amino derivatives are formed in the catalytic reduction of spiropyran derivatives with a nitro group in the chromene ring in benzene solution. In alcohol solutions the nitro group and the 3–4 double bond of the chromene ring are hydrogenated simultaneously.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1320–1326, October, 1977.     

Effects of annulation on the mass spectral behaviour of bicyclo[4.3.0]-3-nonene derivatives: Keto esters and ketones

The fragmentation patterns of the title compounds are shown to depend on the nature of the ring annulation. On ionization the cis-annulated isomers lose a molecule of benzene in contrast to the corresponding trans isomers which do not. A mechanism involving a participation of the π-electron system in the cleavage of the 5-membered ring is suggested to explain the observed differences.     

Spectroscopy of benzene complexes with perylene and other aromatic species

The fluorescence excitation spectra are reported of complexes of benzene with perylene and anthracene. Some correlations are established between the results of simple potential energy calculations and the experimental data, in regard to the structures and binding energies of a number of different complexes. In particular, while the anthracenebenzene complex is somewhat similar to one postulated form of the benzene dimer where parallel, but displaced rings are found, benzene appears to occupy a center-of-mass position on perylene. The spectrum of perylenebenzene also shows evidence of strong coupling between internal modes of the two molecules near 1600 cm⁻¹. The other major perturbation of the spectrum involves damping of the out-of-plane “butterfly” motion of perylene by the adsorbed benzene molecule. The principal low-frequency mode, known to be a v = 0 → v = 2 transition in the bare molecule, at 95 cm⁻¹, is replaced in the benzene 1:1 and 2:1 complexes by a transition, at 68 cm⁻¹. Furthermore, unlike the bare molecule, the ground state frequency of the perturbed out-of-plane mode is very similar to that of the excited state. Indications from these data support the idea that the equilibrium out-of-plane distortion of perylene in a complex with benzene is rather different from that observed in the bare perylene molecule.     

Photochromic Properties of ortho-Methylnitrobenzothiazoles in Solution

Isomeric benzothiazoles having the nitro and methyl groups ortho to each other are converted into tautomeric aci-nitro derivatives on irradiation in heptane solution; in water, the corresponding more deeply colored anions are formed. The efficiency of photochromic transformations strongly depends on the position of the nitro and methyl groups in the benzene ring of the benzothiazole molecule.