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921.
For the first time the computed mechanisms for the novel reaction of 2-naphthol with N-methyl-N-phenylhydrazine, leading to 1-amino-2-naphthol (Tang et al., J Am Chem Soc 2008, 130, 5840), have been investigated using the density functional theory. Four distinct possible pathways were evaluated: two amination mechanisms with the attack of NH(2) group respectively at the α-position C1 and β-position C3 atoms of 2-naphthol (pathways 1 and 2) as well as two rearrangement processes with displacement of the phenolic hydroxyl group followed by the benzidine-like rearrangement at the α-position C1 and β-position C3 atoms of 2-naphthol, respectively (pathways 3 and 4). Solvent effect has been tested based on the optimized geometries of the stationary points in solution at the B3LYP/PCM/6-31+G(d,p) level of theory with an averaged dielectric constant of binary solvent. Single-point energies of the optimized structures have been calculated using three hybrid density functionals, B3LYP, MPW3LYP, and B3PW91 with the 6-311++G(3df,2p) basis set. Our computed results clearly manifest that pathway 1 (α-amination) has the highest possibility to occur, with the Gibbs free energies being lower by 6 to 20 kcal/mol compared with the other three pathways, which leads to 1-amino-2-naphthol and N-methylaniline as products. It is in excellent agreement with the experimental observation.  相似文献   
922.
火焰原子吸收光谱法测定红土镍矿中铜、锌、铬含量   总被引:2,自引:0,他引:2  
红土镍矿样品用盐酸、硝酸分解,残渣用焦硫酸钾熔融,在稀盐酸介质中,采用氘灯扣除背景,分别用原子吸收光谱仪于波长324.8,213.9,357.9 nm处,使用空气–乙炔火焰,测量铜、锌、铬的含量。在最佳实验条件下,铜、锌、铬的质量浓度分别在0.50~2.50,0.30~1.50,0.50~4.50 mg/L范围内与吸光度线性关系良好,相关系数r分别为0.9986,0.9943,0.9942。方法检出限铜为0.0067 mg/L,锌为0.0010 mg/L,铬为0.0014 mg/L,加标回收率为95.0%~105.7%。精密度试验验证铜、锌、铬的含量分别在0.01%~0.50%,0.01%~1.00%,0.01%~4.00%范围内重复性和再现性较好。此方法适合于红土镍矿中铜、锌、铬含量的测定。  相似文献   
923.
Density functional theory calculations are performed to study the (hyper)polarizabilities of a series of planar and twisted intramolecular charge transfer molecules (tictoids) with different electron‐donating and electron‐withdrawing groups. Both similarity and difference between the planar and twisted molecules are noted in their (hyper)polarizability variation with respect to substituent and solvent dielectric constant. When compared with dramatic enhancements resulting from geometry twist and solvent effect, substitution to D/A pairs leads to relatively moderate variation in (hyper) polarizability. In addition, tictoids with different substituents may exhibit different solvent effects in their hyperpolarizability magnitudes. Our calculations suggest that the nonlinear optical response of the tictoids could be tuned by appropriately selecting the donor/acceptor pairs and solvents. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012  相似文献   
924.
By means of Abel’s lemma on summation by parts, we derive several infinite series identities, which involve the classical harmonic numbers and their variants.  相似文献   
925.
We consider the small value probability of supercritical continuous state branching processes with immigration.From Pinsky(1972) it is known that under regularity condition on the branching mechanism and immigration mechanism,the normalized population size converges to a non-degenerate finite and positive limit W as t tends to infinity.We provide sharp estimate on asymptotic behavior of P(W≤ε) as ε→ 0+ by studying the Laplace transform of W.Without immigration,we also give a simpler proof for the small value probability in the non-subordinator case via the prolific backbone decomposition.  相似文献   
926.
An experimental investigation of swirl atomizer sprays   总被引:1,自引:0,他引:1  
In our previous studies (Chu et al. in Heat Mass Transf 43(11):1213–1224, 2007), a theoretical model of swirl atomizers was successfully established. From the analysis, the equations for the droplet size, velocity components, the boundary layer thickness and the spray cone angle were deduced based on the fundamental governing equations. The purpose of this study is to further compare the experimental result with the theoretical one already gained by a satisfactory embodiment of series of experiments. The aim is to corroborate the analytical results of the influence of atomizer construction and controlled pressure difference on typical swirl chambers. The results provide the droplet diameter as a function of pressure difference, swirl atomizer geometry, flow rate, spray cone angle. The experimental outputs also show a good confirmation of theoretical results and can also be used for further optimization on existing swirl chambers. Based on the results obtained, an optimization methodology on characteristics of swirl atomizers is proposed with the adjustment of individual design parameter and the matching flow number.  相似文献   
927.
研究在轴向冲击载荷下弹性圆柱壳动态屈曲问题.通过构造哈密顿体系,在辛空间中将临界载荷和动态屈曲模态归结为辛本征值和本征解问题.辛本征解反映了局部的压缩屈曲模态和整体的弯曲屈曲模态,特别是在冲击端为自由支承边界时的特殊屈曲方式.数值结果给出了具体的临界载荷和屈曲模态规律.  相似文献   
928.
唐晓闩  付鹏  陈远奎  王鸿梅  储焰南 《化学学报》2010,68(11):1093-1097
在流动反应管中, 利用高纯N2空心阴极放电制备活性氮, 研究了活性氮与溴分子碰撞反应得到的发射光谱. 在540~800 nm波段观察到了较强的NBr(b1Σ→X3Σ)跃迁发射谱, 在292 nm处观察到了Br2(D'→A')辐射跃迁. 实验结果表明, 得到的NBr(b1Σ)显示出了非弛豫的发射特征, 最高振动能级为ν'=9. 激发态的NBr(b1Σ)是由活性氮中的N(2P)原子与Br2直接反应生成的.  相似文献   
929.
Functionalized ionic liquid samples (bmim-PW12) were synthesized by 1-butyl-3-methyl-imidazolium bromide (bmimBr) and 12-phosphotungstic heteropolyacid (PW12). The sam-ples were annealed at 100-450 oC and were characterized by Fourier transform infrared spec-troscopy, X-ray diffraction, scanning electron microscope, thermal gravity-DTG, brunauer emmett teller, and NH3-temperature programmed desorption. The results showed that the bmim-PW12 samples were crystal and maintained intact Keggin structure. The organic parts of those samples were partly decomposed at a temperature more than 350 oC. The sample annealed at 400 oC exhibited nano-porous structure, strong acidity, and excellent catalytic activity on the esterification of n-butanol with acetic acid. The higher ester yield was ob-tained when the mass ratio of catalyst over the reactants amount was 5% for bmim-PW12 catalyst annealed at 400 oC.  相似文献   
930.
The potassium lithium niobate crystals have been grown up. The shapes of solid-melt interfaces which maintaining the steady growth of the potassium lithium niobate crystals have been described. The optical transmission spectrum of the crystal has been surveyed. The perfected crystals showed good Second Harmonic Generation properties.  相似文献   
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