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91.
K.R. Sridharan J. Ramakrishna K. Ramachandran S.S. Krishnamurthy 《Journal of Molecular Structure》1980
The frequencies and variable-temperature behaviour of 35Cl nuclear quadrupole resonance in three aminocyclophosphazene derivatives are reported. The observed frequencies and multiplicity are correlated with the disposition of the substituents and the crystal structure. The temperature-dependence data are discussed in the framework of Bayer-Kushida-Brown equations and low-lying torsional (librational) frequencies and their average temperature coefficients are estimated. Brown's parabolic equation provides a good fit to the experimental data. Variable-temperature proton FT-NMR measurements (at 270 MHz) have also been carried out. The results are consistent with the NQR data and indicate the presence of two-site chemical exchange of the -NH protons and hydrogen bonding. 相似文献
92.
It is shown that the inclusion of a small amount of primary ionisation makes the solution to the discharge equilibrium problem
single valued. 相似文献
93.
94.
A. Varada Rajulu S. Raja Ratnam R. Ramakrishna Reddy 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,29(1):85-88
The force constants for diatomic molecules and isolated bonds may be expressed by using equalized electro-negativities, bond orders, bond strengths and interatomicdistances. We have studied Mn1H, Mn2H, Co2H, Ni1H, Ni2H, Cu1H, Cu2H, Ag1H, and Ag2H and have determined the proportionality constant d, as well as the Lennard-Jones parameters a and b, for the potential energy functions used by Szöke and calculated the anharmonicity ωeξe and the rotational-vibrational coupling constant αe. The relation between electronegativity and ionization potential has been verified and the variations of molecular parameters with atomic number Z have been studied. 相似文献
95.
Spectroscopic labeling of A, S/T in the 1H-15N HSQC spectrum of uniformly (15N-13C) labeled proteins
A new triple resonance two-dimensional experiment, termed (HC)NH, has been described to generate specific labels on the peaks of alanines and serines/threonines, separately, in the 1H–15N HSQC spectrum of a protein. The performance of the pulse sequence has been demonstrated with a 151 residue protein. The method permits the investigation of local environments around those specific residues without actually having to obtain complete resonance assignments for the entire protein. With this one can envisage use of the technique for studying large protein systems from different points of view. 相似文献
96.
An efficient, cost-effective and environmentally benign synthesis of novel tetracyclic bis-isoxazolopyrroloquinoline derivatives has been developed via one-pot four-component reaction of 4-amino-3-methyl-5-styrylisoxazoles, dimedone, aryl glyoxal monohydrates and 5-amino-3-methylisoxazole by employing water as a reaction medium and acetic acid (AcOH) as a green promoter. The advantages of this protocol are environmentally friendly, metal-free, less reaction time, operational simplicity, high yields, broad substrate scope and easy purification. Most significant of all, this method is green. 相似文献
97.
Sri Krishna Nimmagadda Mingyu Liu Malkanthi K. Karunananda De‐Wei Gao Omar Apolinar Jason S. Chen Peng Liu Keary M. Engle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3963-3967
A palladium(II)‐catalyzed enantioselective α‐alkylation of azlactones with nonconjugated alkenes is described. The reaction employs a chiral BINOL‐derived phosphoric acid as the source of stereoinduction, and a cleavable bidentate directing group appended to the alkene to control the regioselectivity and stabilize the nucleopalladated alkylpalladium(II) intermediate in the catalytic cycle. A wide range of azlactones were found to be compatible under the optimal reaction conditions to afford products bearing α,α‐disubstituted α‐amino‐acid derivatives with high yields and high enantioselectivity. 相似文献
98.
Dongxiao Ji Li Fan Lu Tao Yingjun Sun Menggang Li Guorui Yang Thang Q. Tran Seeram Ramakrishna Shaojun Guo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(39):13978-13982
Structure and defect control are widely accepted effective strategies to manipulate the activity and stability of catalysts. On a freestanding hierarchically porous carbon microstructure, the tuning of oxygen vacancy in the embedded hollow cobaltosic oxide (Co3O4) nanoparticles is demonstrated through the regulation of nanoscale Kirkendall effect. Starting with the embedded cobalt nanoparticles, the concentration of oxygen‐vacancy defect can vary with the degree of Kirkendall oxidation, thus regulating the number of active sites and the catalytic performances. The optimized freestanding catalyst shows among the smallest reversible oxygen overpotential of 0.74 V for catalyzing oxygen reduction/evolution reactions in 0.1 m KOH. Moreover, the catalyst shows promise for substitution of noble metals to boost cathodic oxygen reactions in portable zinc–air batteries. This work provides a strategy to explore catalysts with controllable vacancy defects and desired nano‐/microstructures. 相似文献
99.
Adsorption of Cr(III) from both synthetic and real samples of tannery wastewater treatment's effluent on chitin-humic acid (chitin-HA) hybrid has been carried out. Rate constant and capacity of adsorption of Cr(III) from the synthetic sample were investigated and removal of Cr(III) from the real sample was tested at optimum medium acidity equivalent to pH 3.5. Characterization using Fourier transform infra red (FT-IR) spectroscopy revealed that both COO− and N-acetyl originated from respectively humic acid (HA) and chitin were involved on the adsorption of Cr(III), and hence the Freundlich's multilayer and multi-energy adsorption model was more applicable to treat the adsorption data than the Langmuir's monolayer and mono-energy model. The quantification of adsorption capacity and rate constant using Freundlich isotherm model and first order adsorption reaching equilibrium yielded values of 6.84 × 10−4 mol g−1 (35.57 mg g−1) and 1.70 × 10−2 min−1, respectively. Removal test for the real wastewater treatment's effluent showed that the maximum amount of Cr(III) could be removed by 1 g of chitin-HA hybrid was 2.08 × 10−4 mol or equivalent to 10.82 mg. 相似文献
100.
An I2–DMSO promoted novel and efficient method is described for the synthesis of isatins from 2-aminoaryl methyl ketone. A series of alkyl or aryl isatin derivatives were successfully synthesized under the optimized reaction conditions. 相似文献