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211.
The adsorption of a H2S molecule on the surface of an MgO nanotube was investigated using density functional theory. It was found that H2S molecule can be associatively adsorbed on the tube surface without any energy barrier or it can be dissociated into –H and –SH species overcoming energy barrier of 4.03–7.77 kcal/mol. The associative adsorption is site selective so that the molecule is oriented in such a way that the sulfur atom was linked to an Mg atom. The HOMO–LUMO energy gap of the tube has slightly changed upon associative adsorption, while they were significantly influenced by dissociation process. Especially, the highest occupied molecular orbital of the tube shifts to higher energies which can facilitate electron emission current from the tube surface. Also, energy gap of the tube dramatically decreased by about 0.93–1.05 eV which influences the electrical conductivity of the tube. 相似文献
212.
The mechanism and thermodynamic of NH3 + O2 reaction on the singlet and triplet potential energy surfaces (PES), were carried out using the RMP2 and CCSD (T)//RMP2 theoretical approaches in connection with the 6-311++G(d, p) basis set. Three pre-reactive complexes, 1C1, 1C2, and 3C1 on the singlet and triplet PES were formed between ammonia and molecular oxygen. With variety of pre-reactive complexes, six types of products are obtained, of which two types are found to be thermodynamically stable. The mechanistic properties of all products channels are discussed. Results show that production of HONO + H2 and HN(OH)2 are the main reaction channels in thermodynamic viewpoint with the Gibbs free energy of ?G° = ?34.681 and ?27.153 kcal/mol, respectively. Rate constants of the title reaction over the temperature range of (200–1000 K) show kinetic products are different from thermodynamic products. 相似文献
213.
214.
Diazabicyclo[2.2.2]octane (DABCO) has been used as a mild and efficient catalyst for synthesis of 2‐amino‐3‐cyano naphthopyran derivatives via a one‐pot three‐component reaction of aromatic aldehydes, naphthols, and malononitrile at room temperature. The short reaction times, easy workup, good to excellent yields, and mild reaction conditions make this domino Knoevenagel–Michael reaction both practical and attractive. 相似文献
215.
Saeed Balalaie Hamid Moghimi Morteza Bararjanian Frank Rominger Hamid Reza Bijanzadeh Masoumeh Sheikhahmadi 《Journal of heterocyclic chemistry》2013,50(6):1304-1312
A highly efficient one‐pot synthesis of some new spiro‐2‐aminopyrimidinones via a three‐component reaction of cyclic ketones, methylcyanoacetate or malononitrile, and guanidinium carbonate has been developed through a domino Knoevenagel/Michael/cyclization sequence. The hydrogen bonding capacity of these compounds would make these structures especially stable. Furthermore, the antibacterial study reveals that these types of compounds exhibit good antibacterial activity. 相似文献
216.
The 1:1 imine intermediate generated by the addition of primary amine to chloroacetone derivatives is trapped by N-isocyaniminotriphenylphosphorane in the presence of phenylacetylenecarboxylic acid, leading to the formation of the corresponding iminophosphorane intermediate. Disubstituted 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reactions were completed in neutral conditions at room temperature. The disubstituted 1,3,4-oxadiazole derivatives were prepared in excellent yields. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
217.
Mojtaba Shamsipur Bahram Hemmateenejad Morteza Akhond 《Journal of solution chemistry》2003,32(9):819-829
The electronic spectra of the iodine molecule in binary mixed solvent systems dioxane–cyclohexane and tetrahydrofuran–cyclohexane were subjected to the multivariate curve–resolution analysis. By using the singular value decomposition method, four different species were identified in the binary mixed solvents. The multivariate curve resolution–alternating least-squares (MCR–ALS) method of Tauler was used to extract the concentration profile and pure spectra of the species present in the mixed solvent systems. Evolving factor analysis was used to obtain the initial estimate of the concentration profiles of the components. The MCR-ALS was implemented by using selected constraints, such as, nonnegativity, unimodality, selectivity, and closure, which are applied during each iteration. Several MCR runs were performed by changing constraints to find the results with lowest fitting error and most chemically reasonable spectra and concentration profiles. From the resulting pure spectra for different iodine species and the corresponding concentration profiles, the nature of iodine species detected in the mixed solvent systems and the influence of the nature of cosolvent have been discussed. 相似文献
218.
Keyvan Amini Mushtak A. K. Shiker Morteza Kimiaei 《4OR: A Quarterly Journal of Operations Research》2016,14(2):133-152
In this paper, a trust-region procedure is proposed for the solution of nonlinear equations. The proposed approach takes advantages of an effective adaptive trust-region radius and a nonmonotone strategy by combining both of them appropriately. It is believed that selecting an appropriate adaptive radius based on a suitable nonmonotone strategy can improve the efficiency and robustness of the trust-region frameworks as well as decrease the computational cost of the algorithm by decreasing the required number subproblems that must be solved. The global convergence and the local Q-quadratic convergence rate of the proposed approach are proved. Preliminary numerical results of the proposed algorithm are also reported which indicate the promising behavior of the new procedure for solving the nonlinear system. 相似文献
219.
Mahmood Esna-Ashari Mansour Gholami Mohammad Ali Zolfigol Morteza Shiri Aghil Mahmoodi-Pour Mehdi Hesari 《Chromatographia》2008,67(11-12):1017-1020
In this study, trans-resveratrol levels were determined in 147 Iranian grape cultivars using a modified extraction and gradient HPLC procedure with photodiode array detection. It was found that 41 out of 147 cultivars contained significant levels of trans-resveratrol. The detected amounts ranged from 0.98 to 6.25 mg kg?1 fresh weight with a mean value of 3.59 (white grapes) and 3.08 mg kg?1 (red grapes), respectively. 相似文献
220.
Alireza Mashayekhi Seyed Mahmoud Hosseini Morteza Hassanpour Amiri Naser Namdar Zeinab Sanaee 《Journal of nanoparticle research》2016,18(6):154
Nitrogen doping of vertically aligned carbon nanotubes (VACNTs) using plasma-enhanced chemical vapour deposition has been investigated to improve the supercapacitance performance of CNTs. Incorporating electrochemical measurements on the open-ended nitrogen-doped CNTs, showed the achievement of 6 times improvement in the capacitance value. For nitrogen-doped CNTs on silicon substrate, specific capacitance of 60 F g?1 was obtained in 0.5 M KCl solution, with capacity retention ratio above 90 % after cycled at 0.1 A g?1 for 5000 cycles. Using this sample, a symmetric supercapacitance was fabricated which showed the power density of 37.5 kW kg?1. The facile fabrication approach and its excellent capacitance improvement, propose it as an efficient technique for enhancing the supercapacitance performance of the carbon-based electrodes. 相似文献