OH+C2H2与OH+C2H4加成反应的热力学和动力学

OH基与乙炔(乙烯)的反应是控制大气中OH基浓度的重要化学反应。对反应OH+C_2H_2,1975年Davis等用FP-RF技术测定了反应的速率常数。1977年,Perry又用同样方法对该反应作出了研究;结果表明,此反应的速率常数强烈地依赖于压力,与Davis等人的实验结果不符。对反应OH+C_2H_4,Atkinson等人的实验研究表明,压力在30.0kPa以下,反应的速率常数随压力而改变;而在30.0—88.4 kPa之间,与压力无关.这与前人的结果不同。两个反应的产物也因温度不同而异.此外,上述反应一般是在近101kPa下发生的,而实验结果大多是在低压下获得的。且目前尚无直接的理论计算结果。为此,我们在从头算水平上用统计热力学方法,对反应     

Rate constant for the reaction C2H5 + HBr → C2H6 + Br

RRKM theory has been employed to analyze the kinetics of the title reaction, in particular, the once-controversial negative activation energy. Stationary points along the reaction coordinate were characterized with coupled cluster theory combined with basis set extrapolation to the complete basis set limit. A shallow minimum, bound by 9.7 kJ?mol(-1) relative to C(2)H(5) + HBr, was located, with a very small energy barrier to dissociation to Br + C(2)H(6). The transition state is tight compared to the adduct. The influence of vibrational anharmonicity on the kinetics and thermochemistry of the title reaction were explored quantitatively. With adjustment of the adduct binding energy by ～4 kJ?mol(-1), the computed rate constants may be brought into agreement with most experimental data in the literature, including new room-temperature results described here. There are indications that at temperatures above those studied experimentally, the activation energy may switch from negative to positive.     

OH+ C2H2N←C2H3 + NO→CH3 + NCO反应机理的密度泛函理论研究

应用密度泛函理论研究了反应通道(a)C2H3 NO→CH3 NCO和(b)C2H3 NO→OH C2H2N的反应机理．在B3LYP／6-31G(d)水平上优化了反应物、中间体、过滤态、产物的几何构型，通过频率分析确定了11个中间体和10个过渡态．所有的反应物、中间体、过渡态、产物都在CCSD／6-311 G(d，P)水平上进行了单点能较正．并讨论了反应的异构化过程．计算结果表明10是能量最低的中间体，比反应物的能量低308．479kJ／mol；过渡态1／3，2／5，3／4，4／8比反应物的能量高，其中3／4是能量最高的过渡态，比反应物的能量高91．894kJ／mol．通道(a)和(b)的理论放热值分别为111．059和96．619kJ／mol．     

Cl+C2H6→HCl+C2H5反应的准经典轨线研究

用三原子模型的准经典轨线方法研究了Ｃｌ与Ｃ２Ｈ６（ｖ＝０，ｊ）的反应。计算结果表明，反应产物ＨＣｌ的角度分布基本上为各向同性，其振动分布处于基态，与实验结果相一致。对反应轨线的研究表明，该反应为一直接反应，而且反应碰撞在低及高的碰撞参数下的机理不一样，在低碰撞参数下反应碰撞是直接完成的，产物ＨＣｌ以向后散射为主，转动基本上是冷的，但比高碰撞参数下的热。在高的碰撞参数下则生成短寿命的碰撞复合物，产物     

Theoretical studies of the radical reaction H2CSiH2 + H

Ab initio molecular orbital calculations on the transition states and barrier heights for the addition of atomic hydrogen to silaethylene are carried out. The activation energy for the addition to the silicon site is lower than that to the carbon site, while the exothermicity is smaller.     

BH+2与C2H2反应势能面的量子化学研究

用B3LYP/6-311G(d,p) 密度泛函方法和高级电子相关的CCSD(T)/6-311G(2df,p)偶合簇法研究BH+2与C2H2反应势能面. 结果表明 该势能面上存在(a) H2B+*C2H2, (b) HBCHCH2+, (c) H2BCCH+2和(d) H2*BHCCH+四种异构体, 其中(b)能量最低且在动力学上最稳定, (a), (c)和(d)在动力学上均不稳定; BH+2通过对C2H2的分步亲电加成以及随后的氢迁移和H2消除等反应形成离解产物HBCCH++H2, 该反应不需要活化能且大量放热. 计算结果有助于深入了解BH+2等缺电子硼氢正离子的反应行为.     

·C2H3+O2→HC·O+H2CO 的密度泛函理论研究

应用密度泛函理论研究了@C2H3+O2→HC@O+H2CO的反应机理.在DFT(B3LYP/6-31G*)水平上对反应过程中所有反应物、中间体、过渡态和产物的几何构型进行优化,通过频率振动分析确认中间体和过渡态.计算IRC反应路径的能量,分析了中间体的异构化过程和各主要原子的自旋密度.     

HCO+和HOC+与C2H2气相质子转移反应的理论研究

在 HF,B3LYP和 QCISD(T)水平上研究了 HCO+和 HOC+与 C2 H2 的气相质子转移反应 .结果表明 :高级电子相关效应对研究质子转移过程极为重要 ;HCO+和 HOC+通过质子垂直进攻 C2 H2 的 π-键分别生成中间体 OC· HC2 H+2 和 CO· HC2 H+2 ,最终生成主要产物为π-质子化的乙炔 HC(H) CH+;对于质子转移反应 HOC+比 HCO+更为活泼 .计算结果与实验结果符合得较好 ,这将有助于理解星际化学以及燃烧化学中的质子转移过程     

State-selected ion-molecule reactions: H+2(ν) + He → HeH+ + H and He + H+ + H

Total cross sections for production of HeH⁺ and H⁺ in the reaction of state-selected H⁺₂ (v = 0 to 6) with He at 3.1 eV c.m. collision energy are measured by means of the threshold-photoelectron/photoion coincidence method, using pulsed synchrotron radiation. Both reaction cross sections are observed to rise with vibrational energy. The H⁺/HeH⁺ branching ratio, which is determined directly, remains approximately constant at about 0.3 for v ⩽ 3 and rises gradually for higher levels to reach the value 1.3 for v = 6. For v ⩽ 3 both reactions involve hard-type collisions and result in large-angle scattering. In contrast, at higher v levels, the HeH⁺ becomes essentially forward scattered with respect to the incident He direction, but with a velocity greater than that expected from the spectator stripping model. The H⁺ products are backward scattered with respect to the incident H⁺₂ for v ⩽ 1 and receed faster from the He atom than the H products. This observation directly leads to the conclusion that collision-induced dissociation from v = 0 and 1 involves transitions to the first excited potential-energy surface.     

Capture and dissociation in the complex-forming CH + H2 → CH2 + H, CH + H2 reactions

The rate coefficients for the capture process CH + H(2)→ CH(3) and the reactions CH + H(2)→ CH(2) + H (abstraction), CH + H(2) (exchange) have been calculated in the 200-800 K temperature range, using the quasiclassical trajectory (QCT) method and the most recent global potential energy surface. The reactions, which are of interest in combustion and in astrochemistry, proceed via the formation of long-lived CH(3) collision complexes, and the three H atoms become equivalent. QCT rate coefficients for capture are in quite good agreement with experiments. However, an important zero point energy (ZPE) leakage problem occurs in the QCT calculations for the abstraction, exchange and inelastic exit channels. To account for this issue, a pragmatic but accurate approach has been applied, leading to a good agreement with experimental abstraction rate coefficients. Exchange rate coefficients have also been calculated using this approach. Finally, calculations employing QCT capture/phase space theory (PST) models have been carried out, leading to similar values for the abstraction rate coefficients as the QCT and previous quantum mechanical capture/PST methods. This suggests that QCT capture/PST models are a good alternative to the QCT method for this and similar systems.     

KrF激光诱导BrC2F4Br+C2H4反应

激光诱导化学合成是一有兴趣的课题。不久前已报导了红外激光诱导调聚反应的结果。由于红外激光的加热特性,在许多情况下导致选择性与量子产率的矛盾。因紫外光反应的低温特性,有可能获得较高的选择性。但普通光源是宽带光源,对一个以平方断链为主的链反应,过强的吸收不利于链长的提高,而弱吸收又使反应速度太慢。为此,激光光源是满足最佳吸收的合宜光源。在使用了昂贵的激光光源后,经济上的合理性主要取决于链长     

Pitzer model parameters for sparingly soluble salts from solubility measurements. The systems TlCl+SrCl2+H2O and TlCl+BaCl2+H2O at 25°C

The solubility of thallium(I) chloride has been determined in aqueous solutions of strontium chloride and barium chloride at concentrations up to 1.5 mol kg^–1. The data were analyzed using Pitzer's equations without making explicit assumption of association to ion pairs by assuming =3 instead of =2, with the ⁽¹⁾ term for TlCl being equivalent to the ⁽²⁾ term for 2-2 electrolytes. Best values of ⁽⁰⁾ and ⁽¹⁾ for TlCl are recommended together with K _s , the activity solubility product. These were used to fit the present solubility data and derive the Pitzer model mixture parameters relevant to the systems, _fTIN and _fTINCl (N=Sr, Ba). Mixture parameters for TlCl+MCl+H₂O systems are also derived to complete the parameter base. The fit of the experimental data was found to be worse when higher-order terms for asymmetrical mixing were included in the analysis. Activity coefficients for thallium(I) chloride in the mixtures are derived.     

双电荷离子[C12H12N2O]2+和[C12H12N2S]2+的气相单分子分解反应研究

The unimolecular dissociation reactions of doubly charged ions were reported,which resulted from a tandem mass spectrometer and a reversed geometry double focusing mass spectrometer by electron impact.Mass analyzed ion kinetic energy spectrometry(MIKES) was used to obtain the kinetic energy releases in charge separation reactions of doubly charged ions.The intercharge distances between the two charges at transition states can be calculated from the kinetic energy releases.Transition structures of unimolecular dissociation reactions were infered from MIKES and MS/MS.     

时间分辨红外发射光谱研究C2H3+NO反应体系

The elementary reaction of C2H3＋ NO has been reported for the first time in this paper.C2H3 radical was produced by laser photolysis of vinyl bromide at 248 nm. Vibrationally excited reaction products H2CO,NCO and HCN were observed. Two exothermic reaction channels leading to HCN＋ H2CO and CH3＋ NCO are identified.     

时间分辨红外发射光谱研究C2H3+NO反应体系

C2H3是一个不饱和自由基及烃类化合物燃烧过程中的重要中间体,它的基元反应是影响燃烧过程速率和最终产物的重要反应.已有人在实验和理论方面研究了C2H3和O2,H2等体系[1－12]的基元反应,但迄今为止,我们还没有看到对于C2H3＋NO体系的研究报导.本文报导了用时间分辨傅立叶变换红外发射光谱（TR-FTIR）研究C2H3＋NO基元反应的结果.1实验　　C2H3自由基是在248nm（KrF激光,Lambda,Physik,LPX305i,单脉冲能量约为110mJ）光解C2H3Br产生的.时间分辨傅立叶变换红外发射光谱（FTIR）方法在我们以前的文章中已有介绍[13].实验…     

C2H3Cl分子团簇内部离子-分子反应产生C4H5Cl+的研究

用同步辐射对（Ｃ２Ｈ３Ｃｌ）２分子团簇进行了光电离研究，发现该团簇内部发生了离子－分子化学反应，生成了十分稳定的反应产物Ｃ４Ｈ５Ｃｌ＾＋，不再是ｖａｒｄｅｒＷａａｌｓ弱键络合物，本文对反主尖机理进行了初步探讨。     

Palladium-Catalyzed [2+2+1] Spiroannulation via Alkyne-Directed Remote C−H Arylation and Subsequent Arene Dearomatization

Palladium-catalyzed alkene-directed cross-coupling of aryl iodide with another aryl halide through C−H arylation opens a unique avenue for unsymmetrical biaryl-derived molecules. However, homo-coupling of aryl iodides often erodes the overall synthetic efficiency. Reported herein is a highly chemoselective Pd⁰-catalyzed alkyne-directed cross-coupling of aryl iodides with bromophenols, which was subsequently followed by phenol dearomatization to furnish a very attractive [2+2+1] spiroannulation. Notably, possible homo-coupling of aryl iodides was not observed at all. Mechanistic studies indicated that a five-membered aryl/vinyl palladacycle most likely accounts for promoting the key step of biaryl cross-coupling.     

H+O2(n0, j0)→HO+O及C+H2(n0, j0)→CH+H体系选态反应截面的过渡态理论计算

本文用微正则过渡态理论计算了H+O_2(n_0,j_0)→HO+O和C+H_2(n_0, j_0)→CH+H在ab initio势能面上的选态反应截面σ_(n_0,j_0); E.分析了势能面性质对反应截面的影响。计算结果表明, 在指定反应物分子的振动态n_0、转动态j_0时, 两个反应体系的反应截面随相对平动能的增加先是增加后是减小(j_0=1, n_0=0除外); 在给定相对平动能和反应物分子的转动态j_0时, 随反应物分子的振动量子数n_0的增加, 两个体系的选态反应截面均有较显著的增加, 在指定相对平动能和反应物分子的振动态n_0时, H+O_2体系的选态反应截面随j_0的变化较为复杂, 而C+H_2体系则比较简单(j_0=1除外)。对于H+O_2反应体系, 本文得到的反应截面与实验结果及准经典轨迹理论的计算结果符合得很好。     

气相中二氯苯的双电荷离子[C6H4CI2]^2+和[C6H3CI]^2+的动能谱研究

本文利用质量分析离子动能(MIKES)和碰撞诱导解离(CID)技术, 研究了邻、间、对二氯苯分子在电子轰击质谱(EIMS)中产生的[C6H4CI2]^2+和[C6H4CI]^2+双电荷离子的单分子电荷分离(CS)反应。根据测定和CS反应的动能释放值T和由此估算的反应过渡态的电荷间距的最小值R, 推测过渡态的结构。有趣的是, 可以利用双电荷离子[C6H4CI2]^2+的分解反应区分二氯苯的位置异构体。