The influence of CH…π interaction on hydrogen bonding ability of –CONH<Subscript>2</Subscript> functional group of benzamide

Interplay between CH…π and hydrogen bond interactions of benzamide has been investigated by quantum mechanical calculations. The effect of the substituents on geometrical parameters has also been studied at the B3LYP level with 6-311++G(d,p) basis set. The electron-withdrawing substituents enhance the total interaction energy of the complexes. The results indicated that the cooperativity of interactions leads to extra stability of the ternary complexes. The CH…π interaction and the hydrogen bond energies have been estimated using the electron densities calculated by the atoms in molecules (AIM) method at hydrogen bond critical points. The strength of hydrogen bonding increases in the presence of CH…π interaction in the ternary complexes. The effect of CH…π interaction on the hydrogen bond interaction has also been studied by the natural bond orbital, AIM and the molecular electrostatic potential analyses.     

A time-dependent quantum dynamics investigation of the guanine-cytosine system: a six-dimensional model

The dynamics of the guanine-cytosine base pair has been studied in the time-dependent quantum approach. A six-dimensional model involving the nonlinear three hydrogen bridges has been utilized. The modifications induced in the hydrogen transfer from a base to the other by the explicit inclusion of the out-of-plane hydrogen atom position in the three bridges have been evidenced and the consequences on stacking interaction and base pair opening are considered. The relevance of these aspects in biological properties has been suggested.     

Infrared spectra of formaldehyde complexes with hydrogen bromide,chlorine and iodine chloride

The infrared spectra of the formaldehyde complexes with hydrogen bromide, chlorine and iodine chloride have been studied. The CH-stretching fundamentals of formaldehyde undergo significant blue shifts in these complexes. The shifts are larger in nitrogen than in argon matrices. The hydrogen bromide complex has been studied in mixed argon-nitrogen matrices.     

汽油制氢反应催化剂制备方法研究

对汽油氧化重整制氢反应催化剂制备方法进行了实验 ,研究了双金M N/Al2 O3 预还原与否对汽油制氢反应的活性、生成氢气的选择性及催化剂的稳定性。实验结果表明 ,催化剂的制备方法不同 ,在汽油氧化重制氢反应中催化剂活性、生成氢的选择性不同 ,还原态的好于非还原态的双金属催化剂 ;还原与否对该双金属催化剂的稳定性影响不大。     

Kinetics of growth and metabolism ofClostridium thermosaccharolyticum culture

The kinetics of growth and metabolism of Clostridium thermosaccharolyticum DSM 571 has been studied at varying initial pH and glucose concentration. A weak inhibitory effect of excess glucose on the specific growth rate has been shown. The effect of antibiotics of various classes on culture growth and hydrogen evolution has been studied. Streptomycin and kanamycin resistance of this culture has been revealed as well as the phenomenon of increased hydrogen production in the presence of the above antibiotics. New plasmids, pNB1 (4.9 kb) and pNB2 (2.0 kb), were isolated from C. thermosaccharolyticum DSM 571. The restriction analysis of pNB1 and pNB2 has been performed.     

Ru(III)-EDTA catalyzed oxidation of ascorbic acid by hydrogen peroxide in aqueous solution

The kinetics of oxidation of ascorbic acid to dehydroascorbic acid by hydrogen peroxide catalyzed by ethylenediaminetetraacetatoruthenate(III) has been studied over the pH range 1.50 – 2.50, at 30°C and μ = 0.1 M KNO₃. The reaction has a first-order dependence on ascorbic acid and Ru(III)-EDTA concentrations, an inverse first-order dependence on hydrogen ion concentration, and is independent of hydrogen peroxide concentration in the pH range studied. A mechanism has been proposed in which ascorbate anion forms a kinetic intermediate with the catalyst in a pre-equilibrium step. Ruthenium(III) is reduced to ruthenium(II) in a rate-determining step and is reoxidized with hydrogen peroxide back to the Ru(III) complex in a fast step.     

我国金属氢化物化学研究

综述了我国金属氢化物化学的发展。我国是从５０年代中期开始研究离子型金属氢化物的合成、性能和应用的,发展了一些合成方法,获得了多项中国专利。储氢合金的化学研究是７０年代中期开始的。在储氢合金的化学合成、吸放氢热力学与动力学、储氢合金氢化催化和电化学方面都有较深入的研究,特别是储氢电极合金电化学及其在Ｎｉ／ＭＨ可逆电池中的应用研究,在国家８６３计划强有力的支持下,某些方面进入了国际先进行列。     

Grand canonical monte carlo modeling of hydrogen adsorption on phosphorus-doped open carbon framework

Mechanism of hydrogen adsorption in high surface area carbon-based porous materials has been studied. Influence of chemical modification of the adsorbing surface has been simulated using grand canonical Monte Carlo method. Special attention has been paid to the competition between increasing the surface of open carbon frameworks and heterogeneous distribution of the energy of adsorption. Additionally, it has been shown that the molecular mass of atoms which substitute carbon atoms is an important factor determining the final hydrogen uptake.     

Overtone bands in aniline and its chloro-derivatives--a low concentration study

Overtone spectra of aniline and its o-and m- chloro-derivatives mixed with carbon tetrachloride have been studied at different dilutions. Vibrational frequency and anharmonicity constants for the C-H stretch vibration and for the symmetric and asymmetric N-H stretch vibrations have been determined. The presence of intermolecular hydrogen bonding has been noted in all the three molecules. Intramolecular hydrogen bonding involving N-H...Cl has also been detected in o-chloroaniline.     

The thermal degradation of some fluorine-containing elastomers

Polymers containing both hydrogen and fluorine atoms can give rise to the evolution of hydrogen fluoride (HF) on thermal and thermo-oxidative degradation. This evolution has been studied with the aid of a fluoride ion specific electrode. The effect of formulation has been examined in some detail for a hydrofluoro-elastomer and it has been shown that the yield of HF is greatly affected by changes in formulation. The effect of variation in chemical structure has also been studied by comparing the degradation of hydrofluoro-, perfluoro-, phosphazene- and fluorine-containing siloxane elastomers. The perfluoro elastomer is the most stable, and the phosphazene elastomer the least stable of the polymers examined, although they both give low yields of HF.     

Reductive desulfurization of allylic thiols by HS-/H2S in water gives clue to chemical reactions widespread in natural environments

The reduction of allylic thiols to alkenes by hydrogen sulfide in aqueous solutions, a novel reaction that may explain reduction processes widely occurring in natural environments, has been discovered. Its mechanism has been studied and suggested to follow an S(RN)1-like pathway involving radical intermediates undergoing 1,4 hydrogen shifts. [reaction: see text]     

氨基酸侧链与氧化鸟嘌呤碱基对体系的氢键作用

应用量子化学方法,分别在气相和水溶液中对氨基酸侧链与氧化鸟嘌呤碱基对(8-oxo-G∶C)形成的三体复合物的氢键键能、几何结构、电荷分布及二阶稳定化能进行了研究.结果表明,水溶液的存在削弱了复合物中的氢键强度,电荷分布变化明显,水溶液中形成氢键位点的电荷变化量约为气相中的10倍,而几何结构变化不明显、对于酶与DNA之间的相互作用的研究需在水溶液中进行.水溶液对带电三体复合物中8-oxo-G∶C与氨基酸侧链间的氢键有较大影响,键能平均减小了69.23 k J/mol,不带电复合物仅减小了3.60k J/mol.水溶液中三体复合物中8-oxo-G∶C间的氢键受侧链的影响不大,且与侧链带电与否无关,带电复合物和不带电复合物的氢键强度分别减小了24.57和30.05 k J/mol,且二阶稳定化能越大,其对应的氢键键长越短.     

Triple hydrogen bonding in a circular arrangement: ab initio, DFT and first-principles MD studies of tris-hydroxyaryl enamines

First-principles Car-Parrinello molecular dynamics, ab initio (MP2) and density functional schemes have been used to explore the tautomeric equilibrium in three tris(amino(R)methylidene)cyclohexane-1,3,5-triones (R?=?hydrogen, methyl or phenyl group). The dynamic nature of the cyclic hydrogen bonding has been studied by the first-principles MD method. The comparison of the results obtained by aforesaid methods has been accomplished on the basis of calculations of structural and spectroscopic characteristics of the compounds. The conformational analysis of the studied compounds has been carried out at the MP2/6-31+G(d,p) and B3LYP/6-31+G(d,p) levels of theory. The influence of steric and electronic effects on the cyclic hydrogen bonding has been analysed. The extent of the proton delocalization has been modified by the substituents according to the sequence: hydrogen?<?phenyl?<?methyl. This fact is verified by the spectroscopic and structural data as well as the energy potential curve. A prevalence of the keto-enamine tautomeric form has been observed in the static ab initio and DFT models, and confirmed by the first-principles MD.     

The effect of hydrogen bonding on structural parameters ii. an ab initio study of the monohydrated formamide molecule

Four hydrogen-bonded formamide-water complexes have been studied by ab initio calculations, two where the amino group acts as a donor and two where the carbonyl oxygen is an acceptor. The results indicate that the effect on the conjugated NCO fragment depends on both the type and the energy of the hydrogen bond formed. Although, in all cases the formation of a hydrogen bond leads to increased conjugation, expressed as a shortening of the CN bond and a corresponding lengthening of the CO bond, there is a significant difference in the effect of the two types of hydrogen bonds. This difference may be explained by changes in the electron populations. In two of the complexes the effect of varying the hydrogen bond length has been studied in some detail. It is found that the effect on the conjugated system depends on the length of the hydrogen bond, and analytical expressions have been found for the variations of the CO and CN bond lengths with changes in the hydrogen bond length. Potential functions for the N-H β O and O-H β O hydrogen bonds have also been derived.     

Catalytic behaviour of a Cu(II) complex sorbed on zirconium molybdate in the decomposition of hydrogen peroxide

Summary Zirconium molybdate has been used as a support on which [Cu(NH₃)₄]²⁺ has been sorbed. Its catalytic activity has been studied through hydrogen peroxide decomposition at different temperatures, using different concentrations of hydrogen peroxide and different amounts of catalyst. A probable mechanism is suggested based on kinetic data.     

Quantum-Chemical Study of the Oxidative Ability of Nitro Compounds Using Decomposition of Some Simple Amines in the Presence of Triplet Nitromethane as an Example

The photooxidation of amines with triplet nitromethane has been studied using the uB3LYP/6-311g* method. The activation energies for hydrogen atom abstraction from ammonia and the amino group of methylamine or aniline have been found to be 14.1, 4.9, and 6.3 kJ mol^?1, respectively. Details of the hydrogen atom transfer mechanism have been studied, the structures of transition complexes have been revealed, and noncovalent interaction energies have been evaluated in terms of the theory of atoms in molecules.     

Prospects for Using Photocatalytic Air Cleaning Technology to Provide Safety of Sevoflurane Application to Parturition Anesthesia in Obstetric Hospitals

The product composition of photocatalytic oxidation of vaporized sevoflurane, a next-generation fluorinated inhalation anesthetic, has been studied. It has been found that the final products of oxidation are carbon dioxide and hydrogen fluoride. The possibility of complete chemical absorption of the evolved hydrogen fluoride by a lime absorber during the course of the photocatalytic reaction has been shown. A safe scheme for using photocatalysis is recommended for purifying air to remove vapors of halogen-containing anesthetics under medical hospital conditions.     

Palladium nanoparticles in aqueous solution: Preparation,properties, and effect of their size on catalytic activity

A method has been developed for the preparation of palladium nanoparticles with different sizes of up to 7 nm via the reduction of Pd(II) ions with hydrogen in an aqueous solution on seed metal nanoparticles (2.5 nm). The effect of the size of nanoparticles on their catalytic activity in methyl viologen reduction with molecular hydrogen in an alkaline medium has been studied. It has been found that the specific catalytic activity of palladium nanoparticles is independent of their size.     

Mathematical simulation of atomic hydrogen diffusion transfer through a multilayer metal membrane at finite pressures

Diffusion transfer of atomic hydrogen through multilayer metal membranes has been studied within the lattice model of an ideal gas, with the transfer being described by a set of nonlinear algebraic equations. It has been shown that, for multilayer membranes composed of less than four layers, an analytical expression describing a diffusion flux can be derived. Atomic hydrogen transfer through a membrane consisting of a vanadium layer, the surfaces of which are coated with palladium films, has been analyzed in detail. It has been found that the value of the flux may depend on the transfer direction. The effect of diffusion asymmetry arises at finite pressures of hydrogen on the outer membrane surfaces, when its dissolution in metals is described by nonlinear sorption isotherms. The degree of the diffusion asymmetry increases with a rise in hydrogen pressure and depends on the arrangement of the layers composing a membrane.     

Kinetics of decalin dehydrogenation on Pt/C catalyst

Catalytic dehydrogenation of decalin (decahydronaphtalene), a promising material for hydrogen storage, has been investigated. The amount of hydrogen produced on a Pt (3 wt.%)/C catalyst has been studied as a function of pressure, temperature, and the substrate feed rate in a flow-type reactor. The maximum volume of the released hydrogen is achieved at atmospheric pressure, a temperature of 320 °C and a substrate LHSV of 1 h^–1. The dehydrogenation occurs mainly by conversion of cis(97%) and partial conversion of trans-decalin (66%) with a selectivity of 97% to naphthalene. The amount of the released hydrogen corresponds to the decalin hydrogen capacity (5.5 wt. %). The obtained results are consistent with the calculated thermodynamic characteristics of the studied reaction.