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本文把Levine的态-态热力学函数由振动-振动态推广到振转-振转态, 对A+BC(v, j)→AB(v', j')+C双分子交换反应给出了Gibbs自由能△G^o(v, j→v',j', T)和化学平均常数K(v, j→v', j', T)在谐振子-截锥转子模型下的详细计算公式, 对H+O2(v, j)→HO(v', j')+O作了数值计算, 结果与由实验归纳出的定性规律相符合。利用本文给出的公式不仅可以对化学反应过程描述得更加细致和深刻, 而且可以方便地讨论分子的振动-转动态耦合对化学反应性的影响。 相似文献
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本文把Levine的态-态热力学函数由振动-振动态推广到振转-振转态, 对A+BC(v, j)→AB(v', j')+C双分子交换反应给出了Gibbs自由能△G^o(v, j→v',j', T)和化学平均常数K(v, j→v', j', T)在谐振子-截锥转子模型下的详细计算公式, 对H+O2(v, j)→HO(v', j')+O作了数值计算, 结果与由实验归纳出的定性规律相符合。利用本文给出的公式不仅可以对化学反应过程描述得更加细致和深刻, 而且可以方便地讨论分子的振动-转动态耦合对化学反应性的影响。 相似文献
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There are two different views on the definition of reaction molecularity in physical chemistry textbooks and related literatures so far. We give a deep discussion about this conception herein. Starting with the development of chemical kinetics and the definition of elementary reaction and state-state reaction, we clarify that elementary reaction and state-state reaction are the conceptions belonging to macro-and micro-systems, respectively, and reaction molecularity is also belonging to micro-conception. Based on this conclusion, we think that the more reasonable definition of reaction molecularity should be "the number of chemical particles that take part in a state-state reaction (or an elementary chemi-physical reaction) as a reactant". 相似文献
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本文首次发现在碱性沸石上乙醇参数发生以正丁醇为主产物的双分子缩合反应。在所研究的催化剂中, 含铷的LiX沸石表现出最高的反应选择性。研究表明, 这一碱化反应的活性与催化剂的酸碱性质密切相关。催化剂的碱性对反应起决定作用,但催化剂的碱性太强则不利于反应。 相似文献
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研究表面活性剂分子在水溶液中的聚集行为对模拟生物膜功能和研究分子间相互作用具有重要意义"'.用于形成囊泡双分子层的表面活性剂主要是类似天然磷脂的双烷基链两亲分子,单烷基链两亲分子在引人刚性基团时亦可形成双分子膜k'.含SChiff碱基两亲分子在水溶液中的聚集性质及间、尾链长度对SChiff碱基构象的影响已有报道"'.本文报道了这类分子的另一种重要成膜性质,即改变制备条件,可选择性地得到不同聚集结构和相变温度的双分子膜·实验中所用成膜分子为:CH。(CH。)。;OPh-N-CH-PhO(CH;)n;N"(CH。)。Br-(m-4;n-… 相似文献
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分子内的狄尔斯-阿尔德反应 总被引:1,自引:0,他引:1
继1928年Diels—Alder发现二烯加成反应后,1953年Alder和Sckumaker提出了第一个分子内的Diels-Alder(以下简称IMDX)反应。几十年来在这一领域的研究得到迅速发展,鹾其成为有机合成的强有力的工具。 相似文献
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根据里德堡轨道的类氢nλ特性,对 7Li2实验已观测到的和理论计算给出的68个电子态进行了分类,把这些态划分为核实贯穿里德堡态和核实非贯穿里德堡态.讨论了双电子激发态和里德堡态的微扰,也讨论了这种分类的意义. 相似文献
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The multiple-channel reactions OH + CH3NHC(O)OCH3 --> products are investigated by direct dynamics method. The optimized geometries, frequencies, and minimum energy path are all obtained at the MP2/6-311+G(d,p) level, and energetic information is further refined by the BMC-CCSD (single-point) method. The rate constants for every reaction channels, R1, R2, R3, and R4, are calculated by canonical variational transition state theory with small-curvature tunneling correction over the temperature range 200-1000 K. The total rate constants are in good agreement with the available experimental data and the two-parameter expression k(T) = 3.95 x 10(-12) exp(15.41/T) cm3 molecule(-1) s(-1) over the temperature range 200-1000 K is given. Our calculations indicate that hydrogen abstraction channels R1 and R2 are the major channels due to the smaller barrier height among four channels considered, and the other two channels to yield CH3NC(O)OCH3 + H2O and CH3NHC(O)(OH)OCH3 + H2O are minor channels over the whole temperature range. 相似文献
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The multiple-channel reactions SiH(3) + SiH(CH(3))(3) --> products are investigated by direct dynamics method. The minimum energy path (MEP) is calculated at the MP2/6-31+G(d,p) level, and energetic information is further refined by the MC-QCISD (single-point) method. The rate constants for individual reaction channels are calculated by the improved canonical variational transition state theory with small-curvature tunneling correction over the temperature range of 200-2400 K. The theoretical three-parameter expression k(T) = 2.44 x 10(-23)T(3.94) exp(-4309.55/T) cm(3)/(molecule s) is given. Our calculations indicate that hydrogen abstraction channel R1 from SiH group is the major channel because of the smaller barrier height among five channels considered. 相似文献
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合成氨生产是一个复杂的、具有多变量、非线性的控制工艺过程。其中变换反应是一个受温度、压力、反应物料,甚至气候条件等因素影响的物理、化学过程。稳定而有效地控制与操作该过程显得十分重要,为此为了指导操作、节约蒸汽、稳定生产,我们开发研究了一种用于测试变换... 相似文献
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The Hammond‐Leffler postulate asserts that transition states of exothermic reactions are reactant‐like (early), whereas transition states of endothermic reactions are product‐like (late). Related postulates have been proposed to describe the sensitivity of activation barriers for reactions occurring on catalytic surfaces to the catalyst structure. To evaluate the validity of these postulates for different chemical reactions, a general method for classifying transition states as either early or late is needed. One can envision a dimensionless reaction coordinate that changes continuously and monotonically from 0 to 1 along a minimum energy reaction pathway. The value of the dimensionless reaction coordinate for the transition state (WTS) classifies transition states as (a) early when WTS < 0.5, (b) late when WTS > 0.5, and (c) equidistant between reactants and products when WTS = 0.5. In this article, we derive such a dimensionless reaction coordinate and illustrate its usefulness for several different chemical reactions. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
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A driver program for carrying out nudged elastic band optimizations of minimum energy reaction pathways is described. This approach allows for the determination of minimum energy pathways using only energies and gradient information. The driver code has been interfaced with the GAUSSIAN 98 program. Applications to two isomerization reactions and to a cluster model for H(2) desorption from the Si(100)-2 x 1 surface are presented. 相似文献
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Ab initio molecular orbital theory with the 6-31G(d), 6-31G(d,p), 6-31+G(d), 6-31+G(d,p), 6-31+G(2d,p), 6-311G(d), 6-311G(d,p), and 6-311+G(2d,p) basis sets and density functional theory (BLYP, B3LYP, B3P86, B3PW91) have been used to locate transition states involved in the conformational interconversions of 1,4-dithiacyclohexane (1,4-dithiane) and to calculate the geometry optimized structures, relative energies, enthalpies, entropies, and free energies of the chair and twist conformers. In the chair and 1,4-twist conformers the C-Hax and C-Heq bond lengths are equal at each carbon, which suggest an absence of stereoelectronic hyperconjugative interactions involving carbon-hydrogen bonds. The 1,4-boat transition state structure was 9.53 to 10.5 kcal/mol higher in energy than the chair conformer and 4.75 to 5.82 kcal/mol higher in energy than the 1,4-twist conformer. Intrinsic reaction coordinate (IRC) calculations showed that the 1,4-boat transition state structure was the energy maximum in the interconversion of the enantiomers of the 1,4-twist conformer. The energy difference between the chair conformer and the 1,4-twist conformer was 4.85 kcal/mol and the chair-1,4-twist free energy difference (deltaG degrees (c-t)) was 4.93 kcal/mol at 298.15 K. Intrinsic reaction coordinate (IRC) calculations connected the transition state between the chair conformer and the 1,4-twist conformer. This transition state is 11.7 kcal/mol higher in energy than the chair conformer. The effects of basis sets on the 1,4-dithiane calculations and the relative energies of saturated and unsaturated six-membered dithianes and dioxanes are also discussed. 相似文献