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1.
Electrochemical synthesis of C-N bond-containing compounds(e.g.,urea,amino acid,amide,amine,and their derivates)from CO2/N2and their derivates is emerging as a promising sustainable strategy[1-7].CO2and its derived products,CO,HCOOH,(COOH)2,etc.,could serve as carbon sources(Figure 1)[8].N2,making up 80%of air,is an appealing nitrogen source.However,the low solubility of N2 and the high dissociation energy for the N≡N bond limit its application. 相似文献
2.
《Tetrahedron letters》1987,28(14):1491-1492
Consistent with our hypothesis for a mechanism involving two kinetically-distinct diradical intermediates, the observed effects of styrene α-substituents can be explained as deriving either from steric effects or radical stabilizing effects. 相似文献
3.
For the first time solubility at 25 and 50°C is studied in the CaCl2 + Mg(NO3)2 ↔ Ca(NO3)2 + MgCl2-H2O four-component reciprocal water-salt system in order to determine the feasibility of preparing calcium nitrate and magnesium
chloride.
Original Russian Text ? K.R. Matveeva, O.S. Kudryashova, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54,
No. 7, pp. 1200–1204. 相似文献
4.
Tatiya Sangkhum Okorn Mekasuwandumrong Piyasan Praserthdam Joongjai Panpranot 《Reaction Kinetics and Catalysis Letters》2009,97(1):115-123
The use of nanocrystalline Fe-modified α-Al2O3 prepared by sol–gel and solvothermal method as supports for Pd catalysts resulted in an improved catalyst performance in
selective acetylene hydrogenation. Moreover, the amount of coke deposits was reduced due to lower acidity of the Fe-modified
α-Al2O3 supports. 相似文献
5.
M. A. Ryazanov B. N. Dudkin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(13):2318-2321
The distribution of the acid-base centers on the surface of α-Al2O3 suspension particles was studied by potentiometric titration, and the corresponding pK spectra were constructed. It was inferred that the double electric layer created by the supporting electrolyte substantially
affected the screening of the acid-base centers on the particle surface of the suspension. 相似文献
6.
The energetics of the phenol O–H bond in methanol and the water O–H bond in liquid water were investigated by microsolvation modelling and statistical mechanics Monte Carlo simulations. The microsolvation approach was based on density functional theory calculations. Optimised structures for clusters of phenol and the phenoxy radical with one and two methanol molecules are reported. By analysing the differential solvation of phenol and the phenoxy radical in methanol, we predict that the phenol O–H homolytic bond dissociation enthalpy in solution is 24.3±11 kJ/mol above the gas-phase value. The analysis of the water O–H bond dissociation by microsolvation was based on optimised structures of OH–(H2O)1–6 and –(H2O)1–7 clusters. Microsolvation modelling and statistical mechanics simulations predict that the HO–H bond dissociation enthalpies in the gas phase and in liquid water are very similar. Our results stress the importance of estimating the differences between the solvation enthalpies of the radical species and the parent molecule and the limitations of local models based on microsolvation.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail 相似文献
7.
The fundamental factors contributing toward the stereoselectivity in organocatalyzed asymmetric Michael reaction between aldehydes (propanal and 3-phenyl propanal) and methyl vinyl ketone (MVK) are established by using density functional theory methods. Three of the most commonly employed α-substituted pyrrolidine organocatalysts are examined. Several key stereochemical modes of addition between (i) a model enamine or (ii) pyrrolidine enamines derived from aldehydes and secondary amine to MVK are examined. Among these possibilities, the addition of (E)-enamine to cis-MVK is found to have a lower activation barrier. The stereochemical outcome of the reaction is reported on the basis of the relative energies between pertinent diastereomeric transition states. Moderate selectivity is predicted for the reaction involving pyrrolidine catalysts I and II, which carry relatively less bulky α-substituents dimethylmethoxymethyl and diphenylmethyl, respectively. On the other hand, high selectivity is computed in the case of catalyst III having a sufficiently large α-substituent (diarylmethoxymethyl or diphenylprolinol methyl ether). The enantiomeric excess in the case of 3-phenyl propanal is found to be much higher as compared to that with unsubstituted propanal, suggesting potential for improvement in stereoselectivity by substrate modifications. The computed enantiomeric excess is found to be in reasonable agreement with the reported experimental stereoselectivities. A detailed investigation on the geometries of the crucial transition states reveals that apart from steric interactions between the α-substituent and MVK, various other factors such as orbital interactions and weak stabilizing hydrogen-bonding interactions play a vital role in stereoselectivity. The results serve to establish the importance of cumulative effects of various stabilizing and destabilizing interactions at the transition state as responsible for the stereochemical outcome of the reaction. The limitations of commonly employed qualitative propositions, relying on the steric protection of one of the prochiral faces of enamines offered by the bulky α-substituent, are presented. 相似文献
8.
《The Journal of chemical thermodynamics》2004,36(2):107-113
The standard (p∘=0.1 MPa) molar enthalpy of formation of crystalline 2-hydroxypyridine N-oxide was measured, at T=298.15 K, by static bomb calorimetry and the standard molar enthalpy of sublimation, at T=298.15 K, was obtained using Calvet microcalorimetry. These values were used to derive the standard molar enthalpy of formation of 2-hydroxypyridine N-oxide in gaseous phase, and to evaluate the dissociation enthalpy of the N–O bond. Additionally, high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional have been performed for the three isomers of hydroxypyridine N-oxide in order to confirm the experimental trend for the dissociation enthalpy of the (N–O) bond. 相似文献
9.
The promoting effect of ethanol on the synthesis of N-(2-methylphenyl)hydroxylamine from o-nitrotoluene in Zn/H2O/CO2 system was observed.By adding appropriate amount of ethanol,the selectivity of N-(2-methylphenyl)hydroxylamine increased from 71%to 90%when the reduction was carried out at 25℃under normal pressure of CO2. 相似文献
10.
Diamond composites were prepared by sintering diamond grains with low melting Na2O–B2O3–SiO2 vitrified bonds in air. The influence of ZnO on the wettability and flowing ability of Na2O–B2O3–SiO2 vitrified bonds was characterized by wetting angle, the interfacial bonding states between diamond grains and the vitrified bonds were observed by scanning electron microscope (SEM), and the micro-scale bonding mechanism in the interfaces was investigated by means of energy-dispersive spectrometer (EDS), Fourier transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS). The experimental results showed that ZnO facilitated the dissociation of boron/silicon–oxygen polyhedra and the formation of larger amount of non-bridging oxygen in the glass network, which resulted in the increase of the vitrified bonds' wettability and the formation of –CO, –O–H and –C–H bonds on the surface of diamond grains. B and Si diffused from the vitrified bonds to the interface, and C–C, C–O, CO and C–B bond formed on the surface of sintered diamond grains during sintering process, by which the interfacial bonding between diamond grains and the vitrified bonds was strengthened. 相似文献
11.
The effect of mechanical activation on the structure and thermal reactions of glasses has been studied on the example of Na–Al–Fe
phosphate glasses. These glasses are used in nuclear technology for immobilization of radioactive waste. The glasses were
activated by grinding in a planetary mill. Mechanical activation causes a decrease of the T
g temperature as well as of the glass crystallization temperature. The type of crystalline phases formed and the quantitative
proportions between them are changing. Analysis of inter-atomic interactions in the structure of glass was applied to explain
the observed regularities governing the crystallization of the activated glasses. 相似文献
12.
Quantum-chemical calculations of the H2O2 and F2 molecules using different computational schemes, basis sets, and procedures for the inclusion of electron correlation were performed. High-resolution X-ray diffraction study of the electron density distribution in the crystals of 2,5-dimethyl-2,5-dihydroperoxyhexane and 2,5-dimethyl-2,5-dihydroperoxyhex-3-yne was carried out. Joint analysis of the results obtained showed that the formally covalent O—O and F—F bonds correspond to a specific type of interatomic interaction. This type is intermediate between the shared and closed-shell interactions (the latter are typical of the ionic systems and van der Waals molecules). 相似文献
13.
Solubility in the 2KNO3 + MgCl2 ↔ 2KCl + Mg(NO3)2-H2O four-component reciprocal system was studied for the first time at 25 and 50°C in order to determine the feasibility of
preparing potassium nitrate and magnesium chloride at near-ambient temperatures. 相似文献
14.
15.
K. S. Rejitha T. Ichikawa S. Mathew 《Journal of Thermal Analysis and Calorimetry》2012,107(3):887-892
Thermal behaviour of hexaamminenickel(II) nitrate and tris(ethylenediamine)nickel(II) nitrate have been investigated by means
of simultaneous thermogravimetry/DTA coupled online with mass spectral (MS) studies and temperature resolved X-ray diffraction
(TR-XRD) techniques under inert atmospheric condition. Both the complexes produce highly exothermic reactions during heating
due to the oxidation of the evolved ammonia or ethylenediamine by the decomposition products of Ni(NO3)2. Evolved gas analysis by MS studies detected fragments like NH2 and NH ions with weak intensity. The decomposition of nitrate group generates N, N2, NO, O2 and N2O species. Ethylenediamine (m/z 60) is fragmented to H2 (m/z 2), N (m/z 14), NH3 (m/z 17) and CH2=CH2/N2 (m/z 28) species. The formation of the intermediates was monitored by in situ TR-XRD. The residue of thermal decomposition for
both the complexes was found to be crystalline NiO in the nano range. 相似文献
16.
Mariana Stoica Monica Cldraru Alice Cpritz N. I. Ionescu 《Reaction Kinetics and Catalysis Letters》1996,57(1):81-86
The charge transfer at the interface H2-0.5% Pt/Al2O3 was studied by using the transient response of the AC electrical conductance. The transient response for water and oxygen contaminated surface was of the overshoot-type. 相似文献
17.
18.
S. L. Khursan 《Kinetics and Catalysis》2016,57(2):159-169
The dissociation energy of the O–H bond has been calculated by the homodesmotic reaction method for phenolic compounds, which are well-known antioxidants, including for natural phenols. Use of moderately complex computational levels, such as B3LYP/6-31G(d), is sufficient for reliably estimating the D(O–H) value for phenols within the homodesmotic approach. The O–H bond dissociation energy for monosubstituted phenols has been calculated, and the additive character of the effect of methyl groups on D(O–H) in methylphenols has been demonstrated: the introduction of a CH3 group into the aromatic ring decreases the D value by 7.8 kJ/mol (ortho position), 1.8 kJ/mol (meta position), and 7.6 kJ/mol (para position). The O–H bond strength has been calculated for a number of ubiquinols, selenophens, flavonoids, and chromanols. The D(O–H) value recommended for α-tocopherol is 328.0 ± 1.3 kJ/mol. 相似文献
19.
V. N. Vandyshev 《Russian Journal of Inorganic Chemistry》2010,55(2):312-314
The enthalpies of mixing of aqueous solutions of nickel(II) nitrate in water + formamide + α-alanine mixtures in the range
of existing amide concentrations have been measured calorimetrically. From these data the standard enthalpies of electrolyte
transfer from water into ternary mixtures have been calculated. The type and character of electrolyte transfer isotherms are
discussed on the basis of the heats of transfer of individual ions that were studied earlier, as well as the contributions
into these values that characterize structural changes in the solution and chemical ion-solvent interactions. 相似文献
20.
Quantitative online NMR spectroscopy was used for studying the species distribution in solutions of carbon dioxide in aqueous monoethanolamine (MEA) and diethanolamine (DEA). The mass fraction of the amine in the unloaded solution was 0.2 and 0.3 g/g, respectively, the carbon dioxide loading was up to 1.1 ??molCO2/molamine, temperatures were between 293 and 353 K. A special apparatus was designed that allows preparing the mixtures gravimetrically and applying pressures up to 25 bar to keep the carbon dioxide in solution. It was coupled to a 400 MHz NMR spectrometer by heated capillaries. By using both 1H and 13C NMR spectroscopy quantitative information on the concentrations of the following species were obtained: amine, carbamate, bicarbonate, and carbon dioxide. Due to the fast proton transfer between molecular and protonated amine, only the sum of their concentrations can be determined. Furthermore, a byproduct, 2-oxazolidone, was observed and quantified. The experimental data were used for developing a thermodynamic model of the studied electrolyte solutions based on the extended Pitzer GE-model. In the model development, also vapor–liquid equilibrium data from the literature were included. The model gives reliable results both for the species distribution and the vapor–liquid equilibrium of the studied mixtures. 相似文献