Calculation of henry constants for the adsorption of isomeric phenylenediamines on graphitized thermal carbon black

Henry constants for the adsorption of o- and p-phenylenediamines on the surface of graphitized thermal carbon black within the temperature range 433–479 K were calculated by the molecular statistical method. The parameters of the atom-atom potential function of intermolecular interaction between the nitrogen atom in aniline and isomeric phenylenediamines and the carbon atom of the basal face of graphite were determined. It was shown that an intramolecular H bond influenced the geometry and adsorption properties of o-phenylenediamine.     

Metal cluster catalysis. 2. Selective reduction of nitrobenzene catalyzed by rhodium carbonyl cluster anions. Evidence for water gas shift reaction

The rhodium cluster complex, Rh₆(CO)₁₆, has been found to catalyze the homogeneous reduction of nitrobenzene to aniline at temperatures above 80 °C in the presence of N,N-dimenthylbenzylamine, using any one of the following reducing gases: (1) H₂/CO, (2) H₂, (3)CO/H₂O. The reductions are highly selective and aniline was the only product detected. The same result was obtained using Amberlyst A-21 resin beads which contained polymerbound N,N-dimethylbenzylamine moieties which, in turn, immobilize the rhodium clusters. It was shown, by using D₂O, and following deuterium incorporation into the resulting aniline, that the water is the source of hydrogen when CO/H₂O was used. When nitrobenzene is absent, this catalyst system promotes the water—gas shift reaction. Unlike aromatic nitro groups, aliphatic nitro groups were not reduced. However, the water—gas shift reaction was catalyzed. The kinetics of aniline formation were first order in nitrobenzene and the effect of pressure on the reaction is described. Use of the resin catalyst led to lower rates and a remarkably air sensitive catalyst system relative to the homogeneous reactions.     

Thermodynamic characteristics of the adsorption of isomeric molecules of fluoroadamantanes on the surface of the basal face of graphite

The thermodynamic characteristics of adsorption (TCA) for isomeric molecules of mono-, di-, tri-, and tetrafluoroadamantanes were determined for the first time experimentally and by molecular statistics on the surface of graphitized thermal black (GTB). The parameters of atom-atom potential function of pair intermolecular interaction (φ(r)) for F atoms included in fluoroadamantanes with C atoms on the basal face of graphite were calculated for the first time within an atom-atom approximation of the semi-empirical molecular statistical theory of adsorption. The adsorption non-equivalence of F atoms in various positions of an adamantane framework, a consequence of the mutual effect of atoms in a framework molecule, was determined. On the basis of the definite TCA values, the conclusion was drawn as to the possibility of isolation of isomeric fluoroadamantanes under the conditions of gas-adsorption chromatography on GTB.     

Adsorption and separation of isomeric methyl- and dimethylaminoadamantanes on graphitized thermal carbon black

The thermodynamic characteristics of adsorption (TCA) of isomeric molecules of methyl- and dimethylaminoadamantanes on the surface of the basis face of graphite were determined experimentally and calculated by the molecular statistical method. A relationship between the geometric structure of adsorbate molecules and the values of their TCA on graphitized thermal carbon black was established. The data obtained were used for the gas chromatographic identification of the amination products of a mixture of Z,E-isomers of 1,4-dimethyladamantane and 1,3-dimethyladamantane.     

Understanding the electrocatalytic mechanism of self-template formation of hierarchical Co9S8/Ni3S2 heterojunctions for highly selective electroreduction of nitrobenzene

Aqueous electrochemical nitroarene reduction reaction using H₂O as the sustainable hydrogen source is an emerging technology to produce functionalized anilines. However, the development of low-cost electrocatalysts and the fundamental mechanistic understanding of the selective NO-RR still remain challenging. Herein, self-supporting hierarchical nanosheets consisting of high-density Co₉S₈/Ni₃S₂ heterojunctions on Ni foam (Co₉S₈/Ni₃S₂-NF) are constructed via an in situ self-template strategy. With combined advantages of high-loading, high surface exposure, efficient conductivity and unique electronic structure of the Co₉S₈/Ni₃S₂ interface, the as-prepared Co₉S₈/Ni₃S₂-NF exhibits efficient electrocatalytic NO-RR performance, including up to 99.0% conversion and 96.0% selectivity towards aniline, and outstanding functional group tolerance. Mechanistic investigations and theoretical calculations reveal that electron transfer from Ni₃S₂ to Co₉S₈ is beneficial for the co-adsorption of H₂O and nitrobenzene molecules at the interfacial sites, promoting the formation of active hydrogen and subsequent reduction of nitrobenzene. Additionally, the interfacial charge transfer breaks the symmetry of two active Co sites at the Co₉S₈/Ni₃S₂ interface, which markedly reduces the energy barrier for reduction of nitrobenzene to aniline. This work offers a successful example for the interfacial engineering of metal sulfide-based heterojunctions with excellent electrocatalytic nitroarene reduction performance, and also paves the way for the in-depth understanding of the corresponding mechanism.

Electrons transfer from Ni₃S₂ to Co₉S₈ in Co₉S₈/Ni₃S₂ heterojunctions through their interface, which is favourable for the adsorption of H₂O and nitrobenzene onto Co sites for the formation of H* and further protonation of nitrobenzene.     

N‐Meth­yl‐N‐(2‐nitro­phen­yl)nitramine and N‐meth­yl‐N‐(3‐nitro­phen­yl)­nitramine

The structures of the two title isomeric compounds (systematic names: N‐meth­yl‐N,2‐dinitro­aniline and N‐meth­yl‐N,3‐di­nitro­aniline, both C₇H₇N₃O₄) are slightly different because they exhibit different steric hindrances and hydrogen‐bonding environments. The aromatic rings are planar. The –N(Me)NO₂ and –NO₂ groups are not coplanar with the rings. Comparison of the geometric parameters of the ortho, meta and para isomers together with those of N‐meth­yl‐N‐phenyl­nitramine suggests that the position of the nitro group has a strong influence on the aromatic ring distortion. The crystal packing is stabilized by weak C—H⋯O hydrogen bonds to the nitramine group.     

Hydrogen transfer hydrogenation of nitrobenzene to aniline with Ru(acac)3 as the catalyst

Tris(acetylacetonato)ruthenium(III)(Ru(acac)₃) was synthesized with RuCl₃·nH₂O and acetylacetone as raw materials. The structure of Ru(acac)₃ was identified by FI-IR, ¹H NMR, ¹³C NMR, and elemental analysis. It was used in the catalytic hydrogen transfer hydrogenation of nitrobenzene with sodium formate as hydrogen donor. The effects of reaction conditions on the process, such as temperature, time, dosage of catalyst, and kinds of hydrogen donor, were investigated. The optimal reaction parameters were determined as follows: 80 °C, 4.0 h, the substrate nitrobenzene 20 mL, sodium formate 27.20 g, Ru(acac)₃ 0.96 g, the conversion of nitrobenzene is 100.0 %, the yield of aniline and the selectivity to aniline are 96.65 %. The reaction mechanism is proposed and analyzed. It exhibited excellent catalytic properties in the hydrogen transfer hydrogenation of nitrobenzene to aniline.     

The influence of aniline and its derivatives on the corrosion behaviour of copper in acid solution

The inhibiting action of aniline and its derivatives on the corrosion of copper in hydrochloric acid has been investigated, with emphasis on the role of substituents. With this purpose five different anilines were selected: aniline, p-chloro aniline, p-nitro aniline, p-methoxy and p-methyl aniline. The electrochemical and gravimetric results, obtained in the absence and presence of different concentrations of inhibitors, revealed that aniline reduces the corrosion of copper, with a critical concentration of 10^–2 M. Furthermore, the interaction energy calculated as G_ads gave a value of 4.2 kcal mol^–1 indicating physisorption of the organic compound at the copper surface. The results have also shown that substituents, either electron donors (–CH₃, –OCH₃) or, electron acceptors (–NO₂, –Cl) in para position, decrease the inhibition action of aniline. A theoretical study using molecular mechanic and ab initio Hartree Fock methods, to model the adsorption of aniline on copper (100) showed results in good agreement with the experimental data. Aniline adsorbs parallel to the copper surface, showing no preference for a specific adsorption site. On the other hand, from ab initio Hartree Fock calculations, an adsorption energy between 2 kcal/mol and 5 kcal/mol is obtained, which is close to the experimental value, confirming that the adsorption of aniline on the metal substrate is rather weak. In view of these results, the orientation of the aniline molecule with respect to the copper surface is considered to be the dominant effect.     

Investigation of the reaction of quinoline with bromine in nitrobenzene

The reaction of quinoline with bromine in nitrobenzene solvent is investigated using the properties of isomolar series. These properties, viscosity, conductivity, density, depression of the freezing point, are determined using a constant molar concentration of C₉H₇N +Br₂, 0.05 per mole of C₆H₅NO₂. It is shown that the nitrobenzene solution of quinoline forms with bromine a complex with the composition C₉H₇N · Br₂. The molecular conductivity of this complex in nitrobenzene solvent increases with dilution.     

Catalytic and electrocatalytic oxidation of aniline to nitrobenzene over vanadium silicate molecular sieves: VS-1 usingt-butyl hydroperoxide (TBHP) as oxidant

A comparison of the results of catalytic and electrocatalytic oxidation of aniline using VS-1 in the presence of H₂O₂ and TBHP indicates remarkable differences in conversion and selectivity. VS-1 catalyzes the oxidation of aniline selectively to nitrobenzene (73%) in the presence oft-butyl hydroperoxide (TBHP), while azoxybenzene (95.2%) is formed selectively when H₂O₂ is used. Cyclic voltammetric studies show a three-step oxidation of aniline to nitrobenzene in H₂O₂ but in the presence of TBHP only one step is observed. Electrocatalytic oxidation of aniline to nitrobenzene occurs at a potential 700 mV less than that corresponding to H₂O₂ as oxidant along with a selectivity of 91.8%. The enhancement of electrocatalytic rate is attributed to the stabilization of electron deficient transition state.     

Effect of substitution of Fe3+ in CuCr2O4 matrix for the hydrogenation of nitrobenzene

The hydrogenation of nitrobenzene to aniline over reduced Cu(Fe_xCr_2–x)O₄ series of catalysts (where x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) has been studied at 250°C in a fixed bed flow type reactor. All the catalysts were characterized by XRD, IR and DRS analysis and by measurements of electrical conductivity and surface area. The conversion of nitrobenzene to aniline is maximum over the catalysts with composition x=0.4. By comparing the results of reversible and irreversible adsorption of carbon monoxide with hydrogenation activity, it can be concluded that univalent copper at octahedral sites is more active for hydrogenation than metallic copper. The second cations [Cr(III) or Fe(III)] develop their catalytic activity by sharing anionic vacancies.     

Removal of sulfate from wastewater via synthetic Mg–Al layered double hydroxide: An adsorption,kinetics, and thermodynamic study

Sulfate-contaminated water is a major environmental problem that alters the taste of water, disturbs the digestive systems of animals and humans, and erodes both soil and metals. In this study, the layered double hydroxide LDH 4Mg2Al·NO₃ and LDH 8Mg2Al·NO₃ were prepared using a co-precipitation technique, and applied in the adsorption of SO₄^2- from an aqueous solution. The reaction is well described by the Langmuir adsorption model. LDH 4Mg2Al·NO₃ and LDH 8Mg2Al·NO₃ afforded maximum SO₄^2- adsorption values of 135.14 and 92.59 ​mg/g, respectively. The reaction is best explained by a pseudo-second-order mechanism, which suggests that chemisorption is the rate-determining step. The activation energies of LDH 4Mg2Al·NO₃ and LDH 8Mg2Al·NO₃ indicate that the adsorption of SO₄^2- on synthetic LDHs predominantly follows an anion-exchange mechanism, wherein SO₄^2- ions in the aqueous medium replaces intercalated NO₃^- ions in the synthetic LDHs. The thermodynamic parameters (ΔH̊, ΔS̊, and ΔG̊) were also calculated. The reaction was endothermic, and the synthetic LDHs afforded feasible and spontaneous adsorption of SO₄^2-.     

Molecular statistical calculation of thermodynamic characteristics of adsorption of polymantane molecules on the basis face of graphite

The thermodynamic characteristics of adsorption (TCA) of polymantane molecules and their some derivatives on the basis face of graphite were calculated for the first time in terms of the atom-atomic approximation of the semiempirical molecular statistical theory of adsorption. The graphite surface exhibits high structural selectivity to isomeric polymantanes. A model for adsorption of cage molecules on the planar surface was proposed. The model is based on the idea that contributions of atoms of the adsorbate molecule to the total adsorption energy can be discriminated according to the distance of these atoms from the surface of a solid. Advantages and limitations of using the data on adsorption of molecules of isomeric alkanes, including rotamers, for the analysis of equilibrium TCA values of isomeric polymantanes on graphite are discussed. The possibility of separation of representatives of the polymantane hydrocarbon family by gas adsorption chromatography on columns with graphitized thermal carbon black was suggested on the basis of the calculated TCA values and logarithmic retention indices.     

NO_x分子在[Ag]-MAPO-5(M=Si,Ti)分子筛中的吸附

采用密度泛函理论(DFT)研究了银离子交换的硅磷酸铝([Ag]-SAPO-5)和钛磷酸铝([Ag]-TAPO-5)分子筛结构及其对NOx分子的吸附,获得吸附复合物的平衡几何结构参数和吸附能.结果表明,NOx分子以η1-N模式吸附在[Ag]-SAPO-5和[Ag]-TAPO-5分子筛中的结构更稳定,其吸附作用强度的次序为NO2NON2O.[Ag]-SAPO-5和[Ag]-TAPO-5对NO和NO2分子的活化程度要比N2O大.相比[Ag]-AlMOR,[Ag]-SAPO-5和[Ag]-TAPO-5对NOx分子的活化程度较大.还对[Ag]-SAPO-5和[Ag]-TAPO-5分子筛的抗硫、抗水及抗氧化性能进行了研究和分析.另外,通过自然键轨道(NBO)计算,分析了NOx分子与平衡离子Ag+之间的作用机理.     

Monolithic catalysts for hydrogenation of nitrobenzene to aniline: influence of aluminum suspension properties

Aluminum suspensions with different properties were prepared and characterized by UV–Vis spectra, BET, XRD and NH₃-TPD. A layer of Al₂O₃ was coated onto the cordierite monolith by sol–gel method. Pd/Al₂O₃/cordierite monolith catalysts with the same Pd loading and particle size were prepared, and tested by nitrobenzene hydrogenation under solvent-free conditions. The adsorption of nitrobenzene on acid sites might be the primary effect under the reaction conditions, and a good linear relationship between hydrogenation rate and the acid content of the Al₂O₃ layer was observed. Furthermore, the stronger acid sites were responsible for the lower aniline selectivity.

     

Characterization of the vibrational behaviour of a bridge with the coordination number 2: III. The case of nonequivalent bridge bonds

Thirty-one complexes with general formula trans- [Co(NO₂)(AA)₂B] (where AA represents the acetylacetonate anion and B represents a range of variously substituted anilines or pyridines) have been synthesized and their infrared spectra determined. ¹⁵N-labelling of the complexes in which B is aniline and p-toluidine yields assignments of the cobalt-amine stretching frequencies and the internal vibrations of the amino group. Assignments of the cobalt-oxygen and cobalt-nitro stretching frequencies are based on comparison of the spectra with those of [Co(AA)₃] and trans-Na[Co-(NO₂)₂(AA)₂]. The assignments are supported by the nature of the dependence of the frequencies on the electronic effects of the substituents in the aniline and pyridine rings.     

Gas-Phase reactions of NO2− with nitrobenzenes and quinones. Electron transfer,clusters and formation of phenoxide and quinoxide negative ions. Use of NO2 as a negative ion chemical ionization reagent

Negative-ion/molecule reactions in systems containing methane as the major gas (∼ 4 torr), with NO₂ and compounds A at mtorr pressures were studied in a pulsed electron, high pressure mass spectrometer. The compounds A were substituted nitrobenzenes and quinones. All these A compounds have positive electron affinities. Three types of reactions were observed and examined. (1) Electron transfer: A⁻ + NO₂ = A + NO₂⁻. The exothermic electron transfer reactions proceeded with ADO collision rates for exothermicities from 30 to ∼ 10 kcal mol⁻¹. Lower exothermicities led to low collision yields. (2) Adduct formation: NO₂⁻ + A = NO₂⁻·A. The equilibria for adduct formation were determined. Stable adducts are formed when A has hydrogens with partial protic character. The stability of the adducts NO₂⁻·A increased with increase in the electron affinity of A, when A was a substituted nitrobenzene. Substituents that increase the electron affinity of nitrobenzene are electron-withdrawing groups which also increase the protic character of the hydrogens involved in bonding in NO₂⁻·A. (3) Some of the compounds A were converted to phenoxy negative ions on reaction with NO₂⁻. For example, para-dinitrobenzene leads to formation of the para-nitrophenoxide negative ion. The oxy-negative-ion-forming reaction can be isomer specific. The utility of reaction types (1)–(3) is examined from the standpoint of negative ion chemical ionization where the reagent gas is NO₂ in methane and the reagent ion is NO₂⁻.     

Voltammetric determination of N-alkylated anilines by adsorption/extraction at a carbon-paste electrode

The voltammetric behaviour of aniline and some of its N-alkylated derivatives at a carbon-paste (Nujol/graphite) electrode is examined. The N-alkylated anilines, in contrast to aniline, are accumulated at the electrode by a combined adsorption/extraction process. The organic bases are determined in the rane 10^?7?2×10^?6 M after a 2-min preconcentration period by differential pulse voltammetry; N,N-dimethylaniline can be determined in the presence of excess of aniline (10^?5 M) by using medium-exchange. The voltammetric method is used for evaluation of the distribution ratios of the organic bases in the Nujol/aqueous buffer system. The enhancement of the voltammetric signal of each base is correlated with the respective distribution ratio.     

Influence of Intramolecular Interactions on Some Parameters in Adsorption Thin-Layer Chromatography

Abstract

Using the equation connecting the R_M values with the appropriate data of the adsorption process from solutions the values of the parameters characterizing substance ? mobile phase interactions have been calculated for the systems: silica gel-benzene+acetone and silica gel-acetone+methanol.Quinoline, aniline, nitrobenzene, phenol and their derivatives were the chromatographed substances. An influence of the structure of the substance on the parameter values has been examined, special attention being paid to intramolecular effects, mainly those of hydrogen bonds.     

Theoretical enthalpies of formation and structural characterisation of halogenated nitromethanes and isomeric halomethyl nitrites

The structural, energetic, and thermochemical properties of a number of halogenated nitromethanes, CH _n X_3?n NO₂, and the isomeric nitrites, CH _n X_3?n ONO, are investigated, using theoretical ab initio and density functional theory (DFT) electronic structure methods. Analysis of the results and comparison with the maternal species, nitromethane, CH₃NO₂, and methyl nitrite, CH₃ONO, reveal strong dependence of the molecular properties on the halogen induction effect. Opposite trends are obtained in the C??N and C??O bond dissociation energies (BDE) upon halogenation and higher stabilities are calculated for the trans-nitrite isomers, in contrast with the plain alkyl families where the nitroalkanes are the most stable species. Formation enthalpies, ??H _f ^? , at 298 K are calculated for all halogenated isomers.