气相离子—分子反应B3H3^—＋CS2→B2H3S^—＋CS的理论研究

用密度泛函方法B3LYP/6-311 G(d,p)和高级电子相关的偶合簇法CCSD（T）／6－311＋＋G（d,p)研究了气相离子,分子反应B2H2^- CS2→B2H3S－＋CS的机理,结果表明,B2H3－最可能进攻CS2中碳原子形成三元环中间体,随后通过氢迁移和最终消除CS的反应步骤形成硫原子转移产物H3BBS^- CS,反应大量放热且不需要活化能,B2H3^-直接对CS2中硫原子进攻夺取硫原子的反应方式存在一定能垒阻碍,计算结果有助于深入了解B2H3－,B3H6和B4H7－等缺电子硼氢负离子反应行为。     

乙硼烷离子和自由基结构的量子化学研究

用B₃LYP/6-311G(d,p)密度泛函方法对B₂H₅⁺阳离子和B₂H₅^·自由基的几何异构体的空间构型进行了优化,并在此基础上用QCISD(T)/6-311++G(3df,2p)偶合簇法进行了单点能计算和零点能校正.结果表明,B₂H₅⁺单态有2种稳定的几何构型(D_3h,C₁),其中C₁构型是新发现的.B₂H₅⁺三重态阳离子除已知C_s构型外,又发现两种稳定构型(C₁).对于B₂H₅^·自由基体系,共有4种异构体(包括两种新发现的构型C_s),其中,具有单桥结构的C_2v最稳定.用二级多体微扰理论和密度泛函方法对前人所认为稳定的B₂H₅⁺单态的C_2v构型进行了全优化,结果发现该构型始终具有一个虚频,不是稳定构型.对B₂H₅^-阴离子体系的单态和三重态进行的全优化,理论上得出单态时具有C_2v和C_s两种稳定构型,而三重态只有C_2v一种稳定构型.     

硼化合物研究(Ⅲ)——B10H102-、B12H122-以及B3H8-阴离子的二茂铁季铵盐的合成

本文通过B_nH_n^2-(n=10,12)及B₃H₈^-盐分别与C₅H₅FeC₅H₄CH₂N(R)Me₂Cl和Fe(C₅H₄CH₂N(R)Me₂Cl)₂(R=CH₃-,C₂H₅-,n-C₃H₇-,CH₂=CH-CH₂-和CH≡C-CH₂-)在水溶液中进行反应,合成了相应的三十个新的硼烷阴离子衍生物,这些化合物对水稳定性好,B₁₀H₁₀^2-及B₁₂H₁₂^2-衍生物对热、酸、碱和氧化剂均很稳定。研究了反应物之间的用量比例对反应产物的影响。实验结果表明,不论反应物之间的克分子比如何变化,只能得到相应的一种产物(产率90-98％)。     

HCO+NO2反应势能面的理论研究

在B3LYP/6-311G(d,p)和CCSD(T)/6-311G(d,p)水平上给出了HCO+NO₂反应详细的势能面信息.计算结果表明,该反应采用两种无垒进攻方式,分别得到两种加合物H(O)CNO₂和H(O)CONO.找到7种能量低于反应物且合理的产物及相应的反应路径.通过对热力学和动力学的分析,产物HONO+CO(P2,P3),HNO+CO₂(P1)和H+CO₂+NO(P6)的形成更为有利.计算结果同实验相符,且有助于深入了解HCO自由基的化学行为.     

非金属氧化-还原对MO2/MO2-(M=N,S,Cl)的电子转移反应动力学

以Marcus-Hush电子转移理论为基础,提出了用量子化学密度泛函方法研究自交换和异交换电子转移反应的理论方案.在DFTB3LYP/6-311+G(2D)水平上研究了溶液中NO₂/NO₂^-,SO₂/SO₂^-和ClO₂/ClO₂^-等3个氧化-还原对的自交换以及它们之间的6个交叉电子转移反应的动力学性质,获得了与实验较为一致的结果.     

硼化合物的桥原子价及其反应活性的理论研究

根据原子价的量子化学定义,采用3-21G基组的ab initio方法,对B₂H₆及其桥原子取代物H₄B₂X₂(X=F,Cl,OH,NH₂,CH₃)进行几何构型优化,讨论桥原子的成键特征,并计算了B₄H₁₀、B₅H₉和B₅H₁₁等硼氢化合物的原子价,讨论了它们的亲电和亲核取代反应活性。     

B2F2分子异构体结构的量子化学计算研究

采用abinitio方法对B₂F₂分子异构体的结构进行了计算研究,并与Al₂F₂分子进行了比较.结果表明,B₂F₂具有D_∞h对称性,³Σ_g电子态的直线型结构FBBF是B₂F₂分子的最稳定异构体,对文献的结果进行了修正.在UCCSD(T,full)/6－311+G(2df)水平下,F-B和B-B键长分别为0.12942和0.14820nm,振动频率出现在1860.00和1320.62cm^-1处.在UQCISD(T,full)/6－311+G(2df)//UMP2(full)/6－311+G(d)+ZPVE水平下,³Σ_g态的线性FBBF分子的垂直电离势为848.58kJ/mol,而由³Σ_g电子态的BF二聚为³Σ_g态的线性FBBF分子的焓变为59.86kJ/mol,此二聚化反应是放热反应,说明二聚化过程在能量上是有利的.     

CH3SH与NO2的反应机理及动力学

在G3B3,CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p)水平上详细研究了CH3SH与基态NO2的微观反应机理.在B3LYP/6-311++G(d,p)水平得到了反应势能面上所有反应物、过渡态和产物的优化构型,通过振动频率分析和内禀反应坐标(IRC)跟踪验证了过渡态与反应物和产物的连接关系.在CCSD(T)/6-311++G(d,p)和G3B3水平计算了各物种的能量,得到了反应势能面.利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT),分别计算了在200～3000K温度范围内的速率常数kTST,kCVT和kCVT/SCT.研究结果表明,该反应体系共存在5个反应通道,其中N进攻巯基上H原子生成CH3S+HNO2的通道活化势垒较低,为主要反应通道.动力学数据也表明,该通道在200～3000K计算温度范围内占绝对优势,拟合得到的速率常数表达式为k1CVT/SCT=1.93×10-16T0.21exp(-558.2/T)cm3·molecule-1·s-1.     

Ih对称性硼、碳原子簇化合物的从头计算(I)──B32、C2B30及B32H322-的构型及稳定性

本文用从头计算方法研究了含32个顶点的硼烷B₃₂H₃₂^2-及裸原子簇B₃₂与C₂B₃₀的构型、稳定性及反应活性。B₃₂的优化计算结果表明,12个5配位与20个6配位两类硼原子不在同一球面时最稳定,而且所含两种B-B核间距离(R₅₆R₆₆)的优化值验证了Lipscomb的经验数值。B₃₂、B₃₂H₃₂^2-电子结构及原子布居的计算表明骨架成键轨道满足Wade规则。相应的计算还表明,中性BB₃₂H₃₂可能稳定存在,但构型的对称性将低于I_h对称,另外。对C₂B₃₀结合能的计算及前线轨道性质的分析表明,C₂B₃₀热稳定性较高,并且有较强的得电子反应活性。     

CH_3SH+CN微观反应机理的理论研究

采用BMC-CCSD//B3LYP/6-311G(d,p)方法对CH3SH+CN反应机理进行了详细的理论研究.反应中涉及的各稳定点的构型、振动频率和零点能在B3LYP/6-311G(d,p)水平下计算得到,计算结果表明,该反应存在两种反应机理,5条可能的反应通道.SN2机理由于能垒太高,与直接氢抽提机理相比可以忽略.该反应的最可行通道为CN中的C原子进攻SH中的H原子经由一个前期和一个后期分子络合物生成产物CH3S和HCN.计算得到的反应焓变与已有实验值非常吻合.     

Theoretical study on the mechanism of the gas-phase reaction of diborane(3) anion with carbon disulfide

The complex potential energy surface of the gas-phase reaction of HB(H)BH- with CS2 to give three low-lying products [B2H3S]- + CS, [BH2CS]- + HBS, and [BH3CS] + BS-, involving nine [B2H3CS2]- isomers and 12 transition states, has been investigated at the CCSD(T)/6-311++G(d,p)/B3LYP/6-311++G(d,p) level. Our calculations are in harmony with the recent experimental and theoretical results, and reveal some new bonding and kinetic features of this reaction system. Our theoretical results may help the further identification of the products [BH2CS]- + HBS and [BH3CS] + BS- and may provide useful information on the chemical behaviors of other electron-deficient boron hydride anions.     

DFT-GIAO calculations of 19F NMR chemical shifts for perfluoro compounds

The (19)F NMR shieldings for 53 kinds of perfluoro compounds were calculated by the B3LYP-GIAO method using the 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-31++G(d,p), 6-311G(d,p), 6-311++G(d,p), 6-311G(2d,2p), 6-311++G(2d,2p), 6-311++G(2df,2p), 6-311++G(3d,2p), and 6-311++G(3df,2p) basis sets. The diffuse functions markedly reduce the difference between the calculated and experimental chemical shifts. The calculations using the 6-31++G(d,p) basis set give the chemical shifts within 10 ppm deviations from experimental values except for the fluorine nuclei attached to an oxygen atom, a four- and a six-coordinated sulfur atom, and FC(CF(3))(2) attached to a sulfur atom.     

Kinetics of the CN + CS2 and CN + SO2 reactions

Diode infrared laser absorption spectroscopy was used to measure the rate constant (k(1)) of the CN + CS(2) reaction for the first time. k(1) was determined to be substantially pressure dependent with a value k(1) = (7.1 ± 0.2 to 41.9 ± 2.9) × 10(-12) cm(3) molecule(-1) s(-1) over 2-40 Torr at 298 K. The potential energy surface (PES) of the reaction was calculated using an ab initio method at B3LYP/6-311++G(d, p)//CCSD(T)/6-311++G(d, p) level of theory. Both experimental and computational results suggest that collision stabilization of the adduct NCSCS may dominate the reaction. The rate constant of the CN + SO(2) reaction was measured to be very slow with an upper limit of k(2) ≤ 3.1 × 10(-14) cm(3) molecule(-1) s(-1), in disagreement with an earlier reported measurement. The PES of this reaction reveals an entrance barrier against formation of the low energy adduct NCOSO, in agreement with the experimental result.     

Theoretical investigation on the GaCl3-catalyzed ring-closing metathesis reaction of N-2,3-butadienyl-2-propynyl-1-amine: three-membered ring versus four-membered ring mechanism

The gallium chloride (GaCl(3))-catalyzed ring-closing metathesis reaction mechanism of N-2,3-butadienyl-2-propynyl-1-amine has been studied at the Becke three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional (B3LYP)/6-31G(d), B3LYP/6-31+G(d,p), B3LYP/6-311++G(d,p)//B3LYP/ 6-31G(d) and the second-order M?ller-Plesset perturbation (MP2)/6-311++G(d,p)//B3LYP/6-31+G(d,p) levels. It was found that the final metathesis product can be yielded via a three-membered or four-membered ring mechanism. The three-membered ring pathway is favorable due to its low energy barrier at the rate determining step. The whole reaction is stepwise and strongly exothermic.     

氮原子与卤代甲烷反应的直接氢抽提过程研究

利用B3LYP理论研究了N(~4S)+CH_3X(X = H, F, Cl)反应体系的直接氢抽提过 程,分别得到了各反应物、产物和过渡态的优化构型和谐振频率。同时应用了6- 31G(d), 6-311+G(d,p)和6-311+ + G(2d,2p)基组,考察其大小对反应体系中各物 种构型及能量的影响。理论计算表明,随着基组的增加,反应势垒逐渐降低,反应 吸热减少。对比取代甲烷的情形,结果表明反应过程中卤素原子具有典型的诱导效 应,降低了抽提势垒。     

Direct experimental observation of CS2OH.

The first experimental detection of CS(2)OH is reported. CS(2)OH was observed for about one microsecond after its formation, as an intact isolated species in the gas phase. It was generated by electron transfer to the CS(2)OH(+) ion, prepared in the source of a multisector mass spectrometer by suitable ion-molecule reactions. The vertical formation process allowed characterization of CS(2)OH by structural analysis of CS(2)OH(+). Theoretical calculations were performed at the B3LYP/6-311+G(2d,p) and CCSD(T)/aug-cc-pVTZ//B3LYP/6-311+G(2d,p) levels of theory. The computed structure and stability of CS(2)OH and CS(2)OH(+) as well as the energetics of the involved processes satisfactorily fit with the experimental results.     

Kinetics of the multichannel reaction of methanethiyl radical (CH3S*) with 3O2

The CH3S* + O2 reaction system is considered an important process in atmospheric chemistry and in combustion as a pathway for the exothermic conversion of methane-thiyl radical, CH3S*. Several density functional and ab initio computational methods are used in this study to determine thermochemical parameters, reaction paths, and kinetic barriers in the CH3S* + O2 reaction system. The data are also used to evaluate feasibility of the DFT methods for higher molecular weight oxy-sulfur hydrocarbons, where sulfur presents added complexity from its many valence states. The methods include: B3LYP/6-311++G(d,p), B3LYP/6-311++G(3df,2p), CCSD(T)/6-311G(d,p)//MP2/6-31G(d,p), B3P86/6-311G(2d,2p)//B3P86/6-31G(d), B3PW91/6-311++G(3df,2p), G3MP2, and CBS-QB3. The well depth for the CH3S* + 3O2 reaction to the syn-CH3SOO* adduct is found to be 9.7 kcal/mol. Low barrier exit channels from the syn-CH3SOO* adduct include: CH2S + HO2, (TS6, E(a) is 12.5 kcal/mol), CH3 + SO2 via CH3SO2 (TS2', E(a) is 17.8) and CH3SO + O (TS17, E(a) is 24.7) where the activation energy is relative to the syn-CH3SOO* stabilized adduct. The transition state (TS5) for formation of the CH3SOO adduct from CH3S* + O2 and the reverse dissociation of CH3SOO to CH3S* + O2 is relatively tight compared to typical association and simple bond dissociation reactions; this is a result of the very weak interaction. Reverse reaction is the dominant dissociation path due to enthalpy and entropy considerations. The rate constants from the chemical activation reaction and from the stabilized adduct to these products are estimated as functions of temperature and pressure. Our forward rate constant and CH3S loss profile are in agreement with the experiments under similar conditions. Of the methods above, the G3MP2 and CBS-QB3 composite methods are recommended for thermochemical determinations on these carbon-sulfur-oxygen systems, when they are feasible.     

Ab initio study of the atmospheric oxidation of CS2.

The reactions of OH with CS2, OCS, and 3SO and of 3O2 with CS2, SCSOH, and HOSO have been studied by optimizing minima and transition states with B3LYP/6-31+G(d) and carrying out higher-level ab initio calculations on fixed geometries. The combined calculations provide valuable insight into the mechanism for the atmospheric oxidation of CS2. The initial step is the formation of the SCSOH complex (1) which readily adds molecular oxygen to form the SC(OO)SOH complex (8). A key step is the oxygen atom transfer to the sulfur bearing the hydroxyl group which leads directly to OCS plus HOSO. The HOSO + 3O2 reaction has a near zero calculated activation barrier so generation of O2H + SO2 should proceed readily in the atmosphere.     

Ab initio study of the F + CH3NHNH2 reaction mechanism

The F + CH(3)NHNH(2) reaction mechanism is studied based on ab initio quantum chemistry methods as follows: the minimum energy paths (MEPs) are computed at the UMP2/6-311++G(d,p) level; the geometries, harmonic vibrational frequencies, and energies of all stationary points are predicted at the same level of theory; further, the energies of stationary points and the points along the MEPs are refined by UCCSD(T)/6-311++g(3df,2p). The ab initio study shows that, when the F atom approaches CH(3)NHNH(2), the heavy atoms, namely N and C atoms, are the favorable combining points. For the two N atoms, two prereaction complexes with C(s) symmetry are generated and there exists seven possible subsequent reaction routes, of which routes 1, 2, 5, and 7 are the main channels. Routes 1, 2, and 5 are associated with HF elimination, with H from the amino group or imido group, and route 7 involves the N-N bond break. Routes 3 and 6 with relation to HF elimination with H from methyl, and route 4 involved the C-N bond break, are all energetically disfavored. For the C atom, the attack of F results in the break of the C-N bond and the products are CH(3)F + NHNH(2). This route is very competitive.