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a transition state
相关语句
  过渡态
    The S_1(n,π~*) state of acetone decomposes to a n→π~* excited state of acetyl radical and a ground state of methyl radical via a transition state (TS) of C_1 symmetry.
    该反应途经一个C_1对称性的过渡态而分解为一个n→π~*激发态的乙酰基和一个基态的甲基。
短句来源
    The results show that the reaction of CH3 radical with HNCO has three pathways :(1)CH3 radical reacts with HNCO to form a hydrogen-bond complex M of which the relative stable energy is 4.56 kJ·mol-1,and then forms another complex M′ t hrough a transition state TS, and breaks down into CH4 and NCO radical in the en d.
    结果表明,自由基CH3与HNCO分子间反应有三条反应通道,第一为CH3与HNCO分子间经过生成一个稳定化能为4.56kJ·mol-1的含氢键的分子复合物M后,经过渡态TS生成另一个产物复合物M',然后分解为甲烷和NCO自由基;
短句来源
    (2)CH3 radical reacts with HNCO to form a stable trans-intermediate(trans-int), then through a transition state(trans-ts) breaks down into CH3NH and CO .
    第二是CH3与HNCO分子间通过生成稳定反式中间体trans-int,其经过渡态trans-ts分解成产物CH3NH和CO;
短句来源
    (3)CH3 radical reacts with HNCO to form a stable cis-intermediate(cis-int), and then through a transition state(cis-ts) breaks down into CH3NH and CO.
    第三是CH3与HNCO分子间通过生成稳定顺式中间体cis-int,其经过渡态cis-ts分解成产物CH3NH和CO.
短句来源
    (Ⅱ) INTa isomerizes to the three-membered product(P) via a transition state(TSa),in which the energy barrier is 23.22 kJ·mol~(-1).
    然后该中间体经过渡态TSa异构化为一三元环产物P,其势垒为23.22 kJ. m o-l 1。
短句来源
  一个过渡态
    From the results of the calculations, it is a multistep reaction including a transition state and two intermediate states. A positive charge of Br+ transfers to H by means of intermediate [C_6H_6Br]+. In fact, it is a process of electron transfer.
    计算结果表明,这是包括一个过渡态和两个中间态的多步反应,反应过程中Br+所带的正电荷经正离子中间体[C6H6Br]+转移给H,是电子转移过程.
短句来源
  “a transition state”译为未确定词的双语例句
    When H2C= C(OH)Na reacts as a carbenoid, it will have a transition state like structure 2. Compared with CH2 == C(OH)Li,CH2 = C(OH)Na is easier to serve as acyl anion equivalent,but more difficult to react as carbenoid.
    同H_2C=C(OH)Li相比较,H_2C=C(OH)Na碳负离子反应将更突出,发生类卡宾反应则更加困难.
短句来源
    A monoclonal antibody (1D1) is raised against the hap ten (2) ,a transition state analog for the hydrolysis of 2 - (p - methoxy - phenoxy) - tetrahydropyran (1), by immunization and hybridoma techniques and possesses a catalytic capacity for hydrolysis of compound (1) in pH =5.60 at 37℃ with 37 folds rate acceleration.
    以2-[对-(3-羧基)-丙基氧苯]-亚氨基哌啶(2)为半抗原,联接载体蛋白后免疫动物,并经杂交瘤技术获得十株单克隆抗体,其中一株单抗1D_1在pH=5.6,37℃条件下能催化2-(对-甲氧苯氧基)-四氢吡喃(1)缩醛键水解,加速37倍
短句来源
    Another reaction channel is firstly isomerization from H 2CO to trans -HCOH that is followed by the C-site hydrogen abstraction reaction, and the next step is from HOC to HCO via a transition state whose reaction barrier is 348.03 kJ·mol -1 . This is a secondary reaction channel.
    另一条通道是H2 CO异构化为trans-HCOH ,然后C位H迁移 ,最后生成的HOC分子异构化为HCO ,这条通道反应势垒高达348 0 3kJ·mol-1,是一条次要反应通道
短句来源
    In this paper, a reliable Density Functional Theory (DFT) method of B3LYP is employed to investigate three important reaction systems in atmospheric chemistry, and the reaction mechanisms is elucidated using the vibrational mode analysis. A new approach to empirically estimate the energy barrier between an intermediate (1M) and a transition state (TS) is also put forward.
    本文主要用密度泛函理论(DFT)的一种可靠方法B3LYP对大气化学中的3个重要反应用振动模式分析来研究它们的反应机理,并对振动频率与能垒之间的定量关系作了一定的探索。
短句来源
    The activated complex as a transition state in the chemical kinetic processes is actually at a nonequilibrium steady state.
    作为化学反应动力学过程过渡状态的活化给合物 ,实际上处于非平衡定态 .
短句来源
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  a transition state
The higher diffusivity of iron is possibly due to the different bonding by oxygen which causes a transition state in the jumps of Fe2+ ions from one site to the next.
      
The presence of nickel in the film was found in a transition state of Ni+2 and Ni0.
      
The planar four-membered ring isomer , 1, an analog of cyclobutadiene, is a transition state lying 37 kcal/mol above the nonplanar four-membered ring , 3.
      
For both ethyl thiocyanate CH3CH2 - SCN and ethyl selenocyanate CH3CH2 - SeCN, the gaucheform is the global minimum while the trans-conformer is a local minimum and the cis-form is a transition state.
      
Such a transition state is in full accord with the experimental data obtained.3.In the reaction studied the relative amounts of the stereoisomeric ortho adducts are determined mainly by electronic, not steric, effects.
      
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Ab initio MO calculation has been performed in an effort to determine the possible reaction path of the addition reaction of HF on C_2H_4.Two limiting reaction mechanisms have been considered.One is a molecular addition which proceeds stereo-specifically via a cyclic four-center transition state and exclusively occurs with cis stereochemistry.The other is a molecular addition which proceeds via a transition state in which the HF molecule is normal to the plane of ethylene and above the C=C bond midpoint.From...

Ab initio MO calculation has been performed in an effort to determine the possible reaction path of the addition reaction of HF on C_2H_4.Two limiting reaction mechanisms have been considered.One is a molecular addition which proceeds stereo-specifically via a cyclic four-center transition state and exclusively occurs with cis stereochemistry.The other is a molecular addition which proceeds via a transition state in which the HF molecule is normal to the plane of ethylene and above the C=C bond midpoint.From the results of calculation it is found that the first mechanism is the possible reaction path.The calculated activation energy is 58.68kcal/mol(245.32kJ/mol),which is to be compared to the experimental value 54±3kcal/mol.The charge transfer between HF and C_2H_4 in the complex has been discussed in terms of Mulliken's population.It was found that negative charge (electrons) is transferred from C_2H_4 to HF when the intermolecular distance R is much greater or much smaller than R_t (the intermolecular distance in the transition state).But when R is near R_t,we found that the direction of charge transfer is reversed.This phenomenon is explained from a frontier orbital point of view.Furthermore,it was shown that Woodward-Hoffmann rules do not fit to the present case because the fluorine atom brings more than one orbitals into play during the reaction process.

用ab initio分子轨道理论研究和确定氟化氢对乙烯分子型加成反应的可能途径.考虑了两种可能的反应机制。一为经过一个四中心过渡态的顺式加成;另一为经过一垂直过渡态(氟化氢分子轴垂直于C=C双键并在其中点的上方)。计算结果表明(STO-3G和4-31G),前者是可能的反应途径。计算的活化能是58.68kcal/mol(245.52kJ/mol),文献报道值是54±3kcal/mol(225.94±12.56kJ/mol)。分析和讨论了反应过程中Mulliken集居数的变化。比较了过渡态附近该“给一受络合物”中电子得失情况的变化,并用前线轨道理论作了解释。根据反应过程中氟化氢的“非键对”参与情况,说明该顺式四中心加成途径不在Woodward-Hoffmann规则禁阻之列。

The pale yellow title compound 1 underwent photochemical conrotatory ring-closure to give the deep red 7, 7, a-dihydrobenzofuran-5,6-dicarboxylic anhydride 2, which ring-opened back to the title compound in a conrotatory mode on exposure to Ar+ laser (515 nm) and did not show a competable thermal 1, 5-H shift against the photodecolouration process due to the lacking of 1-H in the molecule. The extent of photochemical conversion of 1 into its coloured form 2 was determined as 100% by means of Fischer's method....

The pale yellow title compound 1 underwent photochemical conrotatory ring-closure to give the deep red 7, 7, a-dihydrobenzofuran-5,6-dicarboxylic anhydride 2, which ring-opened back to the title compound in a conrotatory mode on exposure to Ar+ laser (515 nm) and did not show a competable thermal 1, 5-H shift against the photodecolouration process due to the lacking of 1-H in the molecule. The extent of photochemical conversion of 1 into its coloured form 2 was determined as 100% by means of Fischer's method. Thus, the photochemical reaction 1 → 2 was complete. Steady state photochemical analysis revealed the existence of a transition state X somewhere between the excited state of 2 and the ground state of 1 during the photodecolouration process with Ar+ laser. X was transformed into compounds 2 and 1 in the specific rates of 22.43 ms.-1 and 1.11 ms.-1, respectively. A general reaction scheme has been forwarded hitherto to explain the mechanism of photochromic process of 1. Two different reaction pathways were involved in the photocolouration and photodecolouration processes of the title compound.

淡黄色的(E)-2,5-二甲基-3-呋喃乙叉(异丙叉)-丁二酸酐,1,在紫外光作用下同旋闭环生成深红色的闭环体,7,7,a-二氢苯骈呋喃-5,6-二羧酸酐,2,在Ar~+激光(515nm)作用下,2同旋开环成1,由于在2的分子中无1-位氢,因此不发生与光消色反应相竞争的1,5氢迁移反应。用Fischer的方法测定了光化学反应1→2的光化学转化率,发现转化率是100%,证明光发色反应是定量的。对于用Ar~+激光引起的光消色反应进行稳态的光化学分析处理,结果揭示在2的激发态和1的基态之间的某一个能级处有一个过渡态X,X分别以22.43ms~(-1)和1.11ms~(-1)的速率常数转变成化合物2和1,提出一个一般性的反应能量座标以解释俘精酸酐的光致色变过程,化合物1的光发色和光消色反应遵循两条不同的反应路线。

The kinetics and mechanisms of the isomerization reactions of three dialkylthiolato-hexacarbonyldiirons(μ-PhCH_2S)(μ-RS) Fe_2(CO)_6,R=Me(1),Et(2),t-Bu(3)havebeen studied by means of ~1H NMR.The related kinetic parameters have been obtainedand the probable mechanism of the reactions has been proposed.The isomerizationreactions proceed most probably via a transition state involving the bond relaxation ofone S-Fe bond and the rotation of another S-Fe bond.

本文用常规核磁共振方法研究了(苄基硫)(烃基硫)六羰基二铁(烃基为甲基、乙基)和动态核磁共振方法研究了(苄基硫)(叔丁基硫)六羰基二铁的异构化反应动力学,提出了可能的反应机理,讨论了影响反应速率的因素.

 
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