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61.
The mechanism of addition reaction between carbene and epoxyethane has been investigated employing the MP2 and B3LYP/6-311+G*
levels of theory. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the
potential energy surface have been calculated. Based on the calculated results at the MP2/6-311+G* level of theory, it can
be predicted that there are two reaction mechanisms (1) and (2). In the first reaction carbene attacks the atom O of epoxyethane
to form an intermediate 1a (IM1a), which is a barrier-free exothermic reaction. Then, IM1a can isomerize to IM1b via a transition
state 1a (TS1a), where the potential barrier is 48.6 kJ/mol. Subsequently, IM1b isomerizes to a product epoxypropane (Pro1)
via TS1b with a potential barrier of 14.2 kJ/mol. In the second carbene attacks the atom C of epoxyethane firstly to form
IM2 via TS2a. Then IM2 isomerizes to a product allyl alcohol (Pro2) via TS2b with a potential barrier of 101.6 kJ/mol. Correspondingly,
the reaction energies for the reactions (1) and (2) are −448.4 and −501.6 kJ/mol, respectively. Additionally, the orbital interactions are also discussed for the leading intermediate.
The results based on the B3LYP/6-311+G* level of theory are paralleled to those on the MP2/6-311+G* level of theory. Furthermore,
the halogen and methyl substituent effects of H2C: on the two reaction mechanisms have been investigated. The calculated results indicate that the introductions of halogen
or methyl make the addition reaction difficult to proceed. 相似文献
62.
In this paper, we develop the sufficient conditions for the existence of local and global saddle points of two classes of
augmented Lagrangian functions for nonconvex optimization problem with both equality and inequality constraints, which improve
the corresponding results in available papers. The main feature of our sufficient condition for the existence of global saddle
points is that we do not need the uniqueness of the optimal solution. Furthermore, we show that the existence of global saddle
points is a necessary and sufficient condition for the exact penalty representation in the framework of augmented Lagrangians.
Based on these, we convert a class of generalized semi-infinite programming problems into standard semi-infinite programming
problems via augmented Lagrangians. Some new first-order optimality conditions are also discussed.
This research was supported by the National Natural Science Foundation of P.R. China (Grant No. 10571106 and No. 10701047). 相似文献
63.
利用新型荧光标记试剂2-[2-(7H-二苯并[a,g]咔唑-乙氧基)-乙基氯甲酸酯作为柱前衍生化试剂, 在Eclipse XDB-C8反相色谱柱上,采用梯度洗脱,实现了12种脂肪胺类化合物完全基线分离.检测最佳激发和发射波长分别为300和400 nm.通过荧光检测及离子阱大气压化学电离源(APCI Source)正离子模式实现了在线的柱后质谱鉴定.对土壤中脂肪胺类化合物的测定快速、准确,具有良好的重现性.荧光定量检测的回归系数大于0.9991; 检出限为10.1~0.3 fmol. 相似文献
64.
Qing MENG 《数学年刊B辑(英文版)》2019,40(3):429-438
In this paper, the author first introduces the concept of
generalized algebraic cone metric spaces and some elementary results
concerning generalized algebraic cone metric spaces. Next, by using
these results, some new fixed point theorems on generalized
(complete) algebraic cone metric spaces are proved and an example is
given. As a consequence, the main results generalize the
corresponding results in complete algebraic cone metric spaces and
generalized complete metric spaces. 相似文献
65.
66.
《Applied Mathematics Letters》2003,16(3):279-285
This paper studies positive solutions to a class of superlinear (sublinear) fourth-order singular boundary value problems by means of operator approximation theory and fixed point theorems. A necessary and sufficient condition for the existence of C3[0, 1] positive solutions is obtained, which extends and includes some known results. 相似文献
67.
Hydrothermal reactions of three aromatic polycarboxylic acids and the transitional metal cations in the presence of phen and 1,4-bib afford three new coordination polymers: [Cd2(bpp)1.5(Hbpp)(phen)2]n(1), [Mn3(Htptc)2(phen)2(H2O)2]n(2), and {[Cu(btc)0.5(1,4- bib)]·2H2O}n(3)(H2bpp = 2,6-bis(4'-carboxyphenyl)-4-phenylpyridine, H4tptc = terphenyl-2,5,2',5'-tetracarboxylic acid, H4btc = biphenyl-2,2',4,4'-tetracarboxylic acid, phen = 1,10-phenanthroline, and 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene). Their structures have been determined by singlecrystal X-ray diffraction analyses, elemental analyses, IR spectra, and powder X-ray diffraction(PXRD) analyses. In compound 1, the CdII cations are linked by bpp2- to form one ladder structure, based on which a 3D network is constructed with the help of non-covalent interactions. The topology of 2 is a 3D(3,4,5)-connected framework with the Point Schl?fli symbol of(42.6)32(4.62.8)(45.64.8)2. Compound 3 shows an unprecedented 3D(4,4)-connected framework with the Point Schl?fli symbol of(64.82)2(65.8). Moreover, the luminescent property of 1 has been investigated. 相似文献
68.
Tao Liu Ling-Li Han Chun-Mei Du Zhang-Yu Yu 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(7):1085-1090
Dopamine (DA) can be oxidized to dopamine quinone (DAquinone) through a one-step, two-electron redox reaction. The electron transfer property of DA and its supramolecular complex with aspartic acid (Asp) has been investigated by the theoretical calculations. We calculated the standard redox potentials (E o) of DA/DAquinone at the MP2/6-31G(d,p)//B3LYP/6-31G(d,p), MP2/6-31+G(d,p)//B3LYP/6-31+G(d,p), MP2/6-31G(d,p)//B3LYP/6-311G(d,p), and MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) levels. Comparing the experimental value, the redox potentials of DA/DAquinone obtained at MP2//B3LYP/6-311G(d,p) and MP2//B3LYP/6-311+G(d,p) levels can be considered as the upper and lower estimates. DA can form supramolecular complex (DA-Asp) with Asp through hydrogen bond (H-bond). Therefore, the values of 0.631 and 0.628 V obtained at MP2//B3LYP/6-311G(d,p) and MP2//B3LYP/6-311+G(d,p) levels for DA-Asp/DAquinone-Asp can be proposed as the upper and lower estimates of a probable (about 0.630 V) value of the corresponding redox potential. The calculated E o values of DA-Asp/DAquinone-Asp at the four theoretical levels are upper than those of DA/DAquinone, which indicates that the formation of H-bonds weaken the electron-donating ability of DA. 相似文献
69.
Substituent effects on the redox potentials of dihydroxybenzenes: theoretical and experimental study
Tao Liu Meng-Meng Liu Xiao-Wen Zheng Chong-Yang Du Xiang-Yang Cui Lu Wang Ling-Li Han Zhang-Yu Yu 《Tetrahedron》2014
The redox reactions of p-hydroquinone and pyrocatechol undergo a two-proton-two-electron process in aqueous solution. We calculated their redox potentials at the B3LYP/6-311+G(d,p) level, and verified the values by employing cyclic voltammetry experiments. Then we selected seven substituent groups (–F, –Cl, –OH, –COOH, –CN, –NH2, and –NO2 groups) to systematically investigate the substituent effect, including the sort, position, and number of the substituent, on the redox potentials of p-hydroquinone and pyrocatechol. The calculated results show that –NH2 and –OH groups can decrease the redox potentials, while –F, –Cl, –COOH, –CN, and –NO2 groups increase the potential values of p-hydroquinone and pyrocatechol. The calculations can accurately predict the substituent effects on the redox potentials of pyrocatechol and p-hydroquinone. We would expect that the accurate calculation results for the model systems could be applied in the prediction of electrode potentials of other molecules. 相似文献
70.
In this work, we present a general scheme to improve quantum state transfer (QST) by taking advantage of quantum partially collapsing measurements. The scheme consists of a weak measurement performed at the initial time on the qubit encoding the state of concern and a subsequent quantum reversal measurement at a desired time on the destined qubit. We determine the strength qr of the post quantum reversal measurement as a function of the strength p of the prior weak measurement and the evolution time t so that near-perfect QST can be achieved by choosing p close enough to 1, with a finite success probability, regardless of the evolution time and the distance over which the QST takes place. The merit of our scheme is twofold: it not only improves QST, but also suppresses the energy dissipation, if any. 相似文献