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1.
《Tetrahedron: Asymmetry》2001,12(18):2529-2532
Ru-catalyzed hydrogen transfer from propan-2-ol to acetophenone under microwave conditions using monotosylated (R,R)-diphenylethylenediamine as the chiral source afforded (R)-1-phenylethanol in >90% yield and 82% e.e. within 9 min, while use of ephedrine or norephedrine gave the same compound in high yield with 70 and 46% e.e., respectively. t-Butylphenylketone was reduced to (R)-2,2-dimethyl-1-phenyl-1-propanol under the same conditions in close to quantitative yield, although with low enantioselectivity. 相似文献
2.
《Journal of the Less Common Metals》1977,51(1):79-91
Partial thermodynamic parameters for the solution of hydrogen in LaNi5 have been determined by p-c-T methods on unactivated bulk samples of LaNi5. The relative partial molar enthalpy of solution of hydrogen, at infinite dilution of hydrogen, is −33,9 kJ (g atom H)−1 (~425 K). This is more exothermic than the heat of absorption corresponding to the formation of the hydride phase from the hydrogen-saturated intermetallic compound. The partial molar enthalpy of solution becomes more endothermic with hydrogen content in the region of solubility in the pure intermetallic compound. The partial thermodynamic quantities at infinite dilution have been found to vary with the stoichiometry of the LaNi5+x where x varies from −0.2 to + 0.5. The partial molar enthalpy of absorption is most exothermic for the stoichiometric compound. 相似文献
3.
Henrik Junge Francesca Capitta James R. Noyes Matthias Beller 《Tetrahedron letters》2009,50(14):1603-6750
The ruthenium-catalyzed generation of hydrogen from formic acid was investigated in the presence of amines and halide additives. While amidines and halide additives increase the production of hydrogen with [RuCl2(p-cymene)]2, >330 mL hydrogen/h is generated in the presence of [RuCl2(benzene)]2/dppe and N,N-dimethyl-n-hexylamine. 相似文献
4.
Eight N -alkyl-N-V-sulphopropylaniline derivatives have been synthesized and assessed as water-soluble hydrogen donors for the spectrophotometric determination of hydrogen peroxide in the presence of peroxidase. The sodium salts of N-ethyl-N-sulphopropylaniline (ALPS), N-ethyl-N-sulphopropyl-m-toluidine (TOPS) and N -ethyl-N-sulphopropyl-m-anisidine (ADPS) are recommended. They have excellent water solubilities, and the optimum pH range for oxidative condensation with 4-aminoantipyrine in the presence of hydrogen peroxide and peroxidase is 5.5–9.5. The absorbances of the resulting chromogens are 2–3 times higher than that achieved with phenol. The molar absorptivities of the chromogens with 4-aminoantipyrine are 41300 (ALPS, λmax 561 nm), 37400 (TOPS, λmax 550 nm) and 27900 (ADPS, λmax 540 nm). Calibration graphs for the determination of hydrogen peroxide in the presence of a control serum are linear for 7–40 × 10-6 mol H2O2 l-1. 相似文献
5.
The dissolution of hydrogen gas in vanadium-based alloys containing niobium, chromium and titanium was studied by measuring the equilibrium pressure, at various compositions, from 763 to 1125 K. Hydrogen followed Sieverts' law in all the alloys studied up to a hydrogen-to-metal atom ratio of 0.25. The values of the enthalpies of solution of hydrogen for these vanadium-based alloys ranged from −18.5 to −46.8 ± 1.5 kJ (mol H)−1 and the standard entropies of solution of hydrogen ranged from −57.4 to −62.6 ± 5.5 J K−1 (mol H)−1. The present results agree extremely well with a previous low temperature study of these alloys which employed an isopiestic technique to measure indirectly the equilibrium hydrogen pressures. 相似文献
6.
W. Ketterle H. Figger H. Walther 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,13(2):129-137
The visible emission spectra of H3, D2H, H2D and D3 were studied. Triatomic hydrogen molecules were produced by neutralization of fast ion beams in alkali vapors. In addition to the well-known 0-0 bands, weak vibrational bands of the electronic 3p 2 A″ 2 → 2s 2 A′ 1 transition of D3 and D2H were observed and analyzed. From the decay of the emission along the molecular beam lifetimes of excited states were obtained. For all observed states, 3p 2 A″ 2, 3s 2 A′ 1 and 3d, lifetimes strongly depend on the isotopic mixture. Many lifetimes measured were considerably shorter than ab initio predictions of the radiative lifetimes. Thus radiationless decay is important for all these excited states. Predissociation of the 3p 2 A″ 2 state increases with the rotational quantum number. Possible decay channels are discussed. 相似文献
7.
The inelastic neutron scattering (INS) spectrum (350–2000 cm?1) of potassium hydrogen dichloromaleate (solid slate) has been obtained. Two of the normal modes of vibration of the hydrogen bond [γ(OHO) and δ(OHO)] were observed and assigned. No INS band vas(OHO) was observed in the region 500–1300 cm?1. This conflicts with expectations from infrared data. 相似文献
8.
A. J. Yencha M. -W. Ruf H. Hotop 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,29(3):163-177
The energy spectra of electrons released in thermal energy ionizing collisions of metastable helium and neon atoms with hydrogen iodide have been measured with high resolution and low background. The electron spectra, obtained for a mixed He(21 S, 23 S) beam, a pure He(23 S) beam, and a mixed Ne(3s 3 P 2,3 P 0) beam, are all characterized by the formation of theX 2Π i andA 2Σ+ states of HI+. For both He(21 S) + HI and He(23 S) + HI the spectra exhibit some broad features in the medium electron energy range which are attributed to ionization from an additional charge exchanged potential surface (He+ + HI?) in the entrance channel. For the first time, we have detected the low energy electrons in the He(21 S, 23 S) spectra due to autoionization of I** atoms which result from energy transfer to highly excited, dissociative HI** Rydberg states. The HI+ (X)2Π3/2:2Π1/2 fine-structure branching ratios vary significantly with the ionizing agent in a similar way as for the isoelectronic, atomic target case xenon. 相似文献
9.
V. I. Bulavin I. N. V’yunnik 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(9):1495-1498
The experimental ionization constants were used to calculate and analyze the effective short-range potential d ij for HCl, HBr, and HI in n-alcohols from methanol to octanol at 5–55°C. Changes in the d ij and Δ ij G* = N A d ij values depending on temperature, solvent, and anions were explained in terms of the Samoilov concept of short-range solvation. The character of changes in Δ ij G* was shown to be determined by the ratio between the contributions of ion-molecular and intermolecular non-Coulomb interactions, which were, in turn, determined by the structural state of the solvent and solvation of electrolyte particles in solutions of hydrogen halides. 相似文献
10.
Robert S. Walters 《Tetrahedron letters》2005,46(38):6487-6489
2′,3′,4′,5′,6′,7′-Hexahydrodispiro[cyclopropane-1,1′-anthracene-8′,1″-cyclopropane] (1) was prepared by double olefination (Wittig) and double methylenation (Furukawa) of 1,8-dioxo-1,2,3,4,5,6,7,8-octahydroanthracene (4) that was in turn prepared in two steps from 1,3-dibromobenzene. The X-ray structure of 1 shows that the C-9-H of its anthracene core is located 2.6 Å from the centroids of each of the flanking cyclopropane rings. The 1H NMR spectrum of 1 shows that the C-9-H resonance (δ 5.95) falls 0.84 ppm upfield from the C-10-H resonance (δ 6.79). 相似文献
11.
A. V. Oreshkina G. Z. Kaziev A. V. Steblevskii T. Yu. Glazunova 《Russian Journal of Inorganic Chemistry》2013,58(8):906-909
[Co(NH3)6] · H2[NiMo6O18(OH)6] · 6H2O (I) and [Co(NH3)6] · H2[ZnMo6O18(OH)6] · 6H2O (II) have been synthesized and studied by mass spectroscopy, thermogravimetry, and X-ray powder diffraction. The crystals of compounds I and II are monoclinic, Z = 1; for compound I: a = 16.10 Å, b = 5.58 Å, c = 12.22 Å, β = 117.86°, V = 1045.14 Å3, and ρcalcd = 2.26 g/cm3; for compound II: a = 16.12 Å, b = 5.52 Å, c = 12.12 Å, β = 117.90°, V = 1043.21 Å3, and ρcalcd = 2.21 g/cm3. 相似文献
12.
Ab initio GAUSSIAN 80 calculations with two different basis sets (STO-3G and 4–31 G*) were performed on hydrogen bonded cresol isomers for comparison with experimental data from free jet fluorescence excitation spectroscopy. Form-cresol, the calculated barriers for hindered internal rotation of the OH-group and the CH3-group are in good agreement with experiment. The calculations show the trans-linear configuration ofp-cresol·B-clusters (B = H2O, CH3OH) to be more stable than the all-planar configuration. This agrees with CI calculations and microwave spectroscopic investigations of the water dimer. Calculations of both the intermolecular stretch and bend frequencies ofp-cresol·B-clusters show little dependence on the all-planar or trans-linear configuration but a strong dependence on the choice of the basis set. With the minimal basis set STO-3G, the vibrational energies are generally too high. The agreement between the calculated vibrational frequencies from the 4–31 G* basis set and the experimental values is fair. 相似文献
13.
The moment functions of H+2 are computed for internuclear distances up to 5a0 from the dipole osciliator strengths. 相似文献
14.
Spin-lattice relaxation times T1 were measured over a large frequency region for H and D nuclei in the hydrogen bonded complex of trichloroacetic acid and dimethylsulphoxide. The measured relaxation times T1 can be ascribed to the motion of the complex as a whole with a negligible contribution from the association—dissociation process. 相似文献
15.
Ralph G. Pearson 《Theoretical chemistry accounts》1983,64(2):127-136
The ground state of the H 2 + molecule is studied using the equations of classical mechanics and the Einstein quantum condition, J ζ+J μ = h, where J ζ and J μ are the action integrals over a complete cycle of the elliptic coordinates. Strong bonding is found, but the quantitative results are good only for R<0.05 and R>4a 0. The greatest error comes at R eq and results from the coalesence of two classically allowed regions where the electron can exist. 相似文献
16.
A. J. Yencha M. -W. Ruf H. Hotop 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,27(2):131-142
An electron spectrometric study has been performed on HF using metastable helium and neon atoms as well as helium and neon resonance photons. High-resolution electron spectra were obtained for a pure He(23 S) beam, a mixed He(21 S, 23 S) beam, a mixed Ne(3s,3 P 2,3 P 0) beam, and for HeI and NeI VUV light. From the comparison of vibrational populations of HF+ (X 2£ i ,v′) and HF+ (A 2Σ+,v′) produced by He(23 S) metastables and HeI resonance photons, we conclude that there is only a slight perturbation of the HF (X 1Σ+) potential in He(23 S) Penning ionization; no perturbation is found for HF+ (X 2Π i ,v′) formation from Ne(3 P 2,0) metastable ionization of HF. For He(21 S)+HF theX- andA-ionic state vibrational peak shapes are substantially broader than in the He(23 S)+HF case pointing to an additional, charge exchanged interaction (He++HF?) in the entrance channel of the former system. The vibrational population found for NeI α photoionization of HF for formation of HF+ (X 2Π i ,v′) is found to differ considerably from that for NeI β photoionization and from the Franck-Condon factors for unperturbed HF(X 1Σ+) and HF+ (X 2Π i ) potentials suggesting the presence of an autoionizing superexcited state of HF in the energy vicinity of the NeI α resonance photons. The HF+ (X)2Π3/2:2Π1/2 fine-structure branching ratios vary significantly with the ionizing agent in a similar way as previously found in HCl and HBr. 相似文献
17.
A. J. Yencha J. Ganz M. -W. Ruf H. Hotop 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,14(1):57-76
An electron spectrometric study has been performed on HCl using metastable helium and neon atoms as well as neon resonance photons. High resolution electron spectra were obtained with two different beam apparatuses for a mixed He(21 S, 23 S) beam, a pure He(23 S) beam, and, for the first time, state-selected pure Ne(3s 3 P 2) and pure Ne(3s 3 P 0) beams, and for NeI resonance photons. For the system He(23 S)+HCl the vibrational populationsP(υ′) of the formed HCl+ (X 2∏ i , υ′) and HCl+ (A 2Ω+, υ′) ions are found to differ from the Franck-Condon factors for unperturbed potentials, indicating slight bond stretching in HCl upon He(23 S) approach. For He(21 S)+HCl the vibrational peak shapes and vibrational populations are substantially different from the He(23 S) case, pointing to an additional, charge exchanged interaction (He++HCl?) in the entrance channel of the former system. For the first time, we have detected the electrons in both the He(21 S)+HCl and He(23 S)+HCl spectra associated with the major mechanism for the formation of Cl+ ions: energy transfer to repulsive HCl** Rydberg states, dissociating toH(1s) and autoionizing Cl**(1 D 2 nl) atoms. For both Ne(3 P 2)+HCl and Ne(3 P 0)+HCl, the populationsP(υ′) of both final molecular states HCl+ (X, A) agree closely with the Franck-Condon factors at the average relative collision energyē coll=55 meV and, for HCl+ (A 2Ω+), also atē coll=130 meV. 相似文献
18.
G. Perny 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1988,10(1):93-98
We introduce here a new concept, the “Ef” products, i.e. the products of the atomic energy levels by the corresponding oscillator strengths, which are observables in the Heisenberg's sense. These fundamental atomic quantities are quite available in the literature. It is shown that, by building up for each atom of the diatomic molecule an atomic matrix of the form (M) nl,n′l′ a =(E nl ·f nl→n′l′ ) one is able to obtain in a straightforward way the oscillator strength of the excited molecule,f mol, from the equation defining the resultant molecular matrix [(M) nl, n′l′ a ]2={(M) (2) m } nl,n′l′ . This concept has been applied to H2 and O2. Very good agreement between the values calculated in this paper and those given theoretically for H2 using LCAO-MO-CI method and experimentally for O2 by other authors is obtained. 相似文献
19.
Suchitra Datta 《Tetrahedron》2009,65(1):77-82
The lactam groups of dipyrrinones avidly engage in amide-amide hydrogen bonding to form dimeric association complexes in non-polar solvents (in CHCl3, KD ∼25,000 M−1 at 22 °C). The corresponding thioamides (dipyrrinthiones), prepared from dipyrrinones by reaction with Lawesson's reagent, also form intermolecularly hydrogen-bonded dimers in non-polar solvents, albeit with much weaker association constants (in CHCl3, KD ∼200 M−1 at 22 °C). When a carboxylic acid group is tethered to C(9) of the dipyrrinone, as in the hexanoic acid of [6]-semirubin, tight intramolecular hydrogen bonding between the carboxylic acid group and the lactam moiety (intramolecular Kassoc ?25,000) is found in CHCl3 with no evidence of dimers. In contrast, the analogous dipyrrinthione, [6]-thiosemirubin, eschews intramolecular hydrogen bonds, as determined using NMR spectroscopy and vapor pressure osmometry, preferring to form intermolecularly hydrogen-bonded dimers of the thioamide-thioamide type. 相似文献
20.
Photodissociative production of ion pairs from H2 has been observed in the wavelength range 706–718 A at spectral resolution of 0.4 and 0.22 A. From measured thresholds for production of H? from H2 molecules in each of the three lowest rotational states, the lower bound EA(H) ? 0.754 ± 0.002 eV is obtained, in excellent agreement with the theoretical electron affinity of 0.75421 eV. For formation of D? from D2, a threshold assigned to molecules in the rotational state J = 2 has been measured, from which the bound EA(D) ? 0.757 ± 0.005 eV is obtained. Negative ion yield curves are presented for hydrogen. 相似文献