O(~3P)+HBr(DBr)反应的含时量子散射计算(英文)

基于LEPS势能面, 用三维含时量子波包法对O(3~P)+HBr(DBr)反应进行了准确的动力学计算. 计算的结果表明, 振动激发对这个反应是有效的, 而转动激发在某一能量范围内具有方位效应. 计算得到了该反应的速率常数和反应截面, 速率常数kO+HBr的计算值同实验值符合得很好. 通过对相应结果的对比, 可以发现这个反应具有比较明显的同位素效应.     

HCF(X~1A’)+SO2反应的动力学研究

用激光光解-激光诱导荧光方法研究了室温下(T＝293 K) HCF(X^~1A^’)自由基与SO₂分子的反应动力学. 实验中HCF(X^~1A^’)自由基是由213 nm激光光解HCFBr₂产生的, 用激光诱导荧光(LIF)检测HCF(X^~1A^’)自由基的相对浓度随着反应时间的变化, 得到此反应的二级反应速率常数为: k＝(1.81±0.15)×10^－12 cm³•molecule^－1•s^－1, 体系总压为1862 Pa. 高精度理论计算表明, HCF(X^~1A^’)和SO₂分子反应的机理是典型的加成-消除反应. 我们运用RRKM-TST理论计算了此二级反应速率常数的温度效应和压力效应, 计算结果和室温下测定的二级反应速率常数符合得较好.     

HCF(X~1A’)+SO2反应的动力学研究

用激光光解-激光诱导荧光方法研究了室温下(T＝293 K) HCF(X^~1A^’)自由基与SO₂分子的反应动力学. 实验中HCF(X^~1A^’)自由基是由213 nm激光光解HCFBr₂产生的, 用激光诱导荧光(LIF)检测HCF(X^~1A^’)自由基的相对浓度随着反应时间的变化, 得到此反应的二级反应速率常数为: k＝(1.81±0.15)×10^－12 cm³•molecule^－1•s^－1, 体系总压为1862 Pa. 高精度理论计算表明, HCF(X^~1A^’)和SO₂分子反应的机理是典型的加成-消除反应. 我们运用RRKM-TST理论计算了此二级反应速率常数的温度效应和压力效应, 计算结果和室温下测定的二级反应速率常数符合得较好.     

CH3OCF2CF2OCH3+Cl的反应机理及动力学性质

利用密度泛函理论直接动力学方法研究了反应CH₃OCF₂CF₂OCH₃+Cl的微观机理和动力学性质. 在BB1K/6-31+G(d,p)水平上获得了反应的势能面信息, 计算中考虑了反应物CH₃OCF₂CF₂OCH₃两个稳定构象(SC1和SC2)的氢提取通道和取代反应通道. 利用改进的正则变分过渡态理论结合小曲率隧道效应(ICVT/SCT)计算了各氢提取通道的速率常数, 进而根据Boltzmann配分函数得到总包反应速率常数(k_T)以及每个构象对总反应的贡献. 结果表明296 K温度下计算的k_T(ICVT/SCT)值与已有实验值符合得很好. 由于缺乏其他温度速率常数的实验数据, 我们预测了该反应在200-2000 K温度区间内反应速率常数的三参数表达式: k_T=0.40×10^-14T^1.05exp(-206.16/T).     

C2H3与CH3F氢抽提反应机理与动力学性质

采用双水平直接动力学方法对C₂H₃与CH₃F氢抽提反应进行了研究. 在QCISD(T)/6-311++G(d, p)//B3LYP/6-311G(d, p)水平上, 计算的三个反应通道R1、R2和R3的能垒(ΔE^≠)分别为43.2、43.9和44.1 kJ·mol^-1, 反应热为-38.2 kJ·mol^-1. 此外, 利用传统过渡态理论(TST)、正则变分过渡态理论(CVT)和包含小曲率隧道效应(SCT)的CVT, 分别计算了200-3000 K温度范围内反应的速率常数k^TST、k^CVT和k^CVT/SCT. 结果表明: (1) 三个氢抽提反应通道的速率常数随温度的增加而增大, 其中变分效应的影响可以忽略, 隧道效应则在低温段影响显著; (2) R1反应是主反应通道, 但随着温度的升高, R2反应的竞争力增大, 而R3反应对总速率常数的影响很小.     

氢抽提反应CHBr2+HBr→CH2Br2+Br的直接动力学研究

采用直接动力学方法,对CHBr2+HBr→CH2Br2+Br反应通道进行了理论研究,在B3LYP/6-311+G(d,p)水平下获得了优化几何构型、频率以及最小能量路径,更精确的单点能在B3LYP/6-311++G(3df,2pd)水平下完成.利用正则变分过渡态理论,结合小曲率隧道效应校正方法计算了反应通道在220 K～2 000 K温度范围内的速率常数.在整个反应区间,隧道效应对反应的影响比较大;变分效应在低温时有一定的影响,在高温区间的影响很小可以忽略.计算得到的速率常数和已有实验值很好地吻合.     

抗氧剂亚硫酸钠、亚硫酸氢钠及焦亚硫酸钠氧化反应速率常数的测定

为评价抗氧剂的抗氧化能力, 测定了抗氧剂亚硫酸钠、亚硫酸氢钠及焦亚硫酸钠在水溶液中与氧反应的速率常数. 在溶液中连续通入足量的氧气, 维持溶解氧浓度恒定. 用碘量法测定亚硫酸钠、亚硫酸氢钠及焦亚硫酸钠在水溶液中不同时刻的浓度, 用氧电极测定溶液中溶解氧的浓度, 作出亚硫酸钠、亚硫酸氢钠及焦亚硫酸钠的降解曲线, 计算亚硫酸钠、亚硫酸氢钠及焦亚硫酸钠氧化反应速率常数. 结果表明, 亚硫酸钠、亚硫酸氢钠及焦亚硫酸钠在水溶液中与氧的反应均为零级反应. 由于在溶液中这三种抗氧剂存在解离平衡, 当溶液的pH值相同时这三种抗氧剂实质上是一样的, 其平均表观反应速率常数在25 ℃温度和pH 6.8, 4.0及9.2条件下分别为(1.34±0.03)×10^－3, (1.20±0.02)×10^－3和(6.58±0.02)×10^－3 mol•L^－1•h^－1.     

烷基自由基β位裂解反应类反应势垒与速率常数的精确计算

提出反应类等键方法并用于高温燃烧机理中一类重要反应——烷基自由基β位裂解反应的反应势垒和速率常数的精确校正计算. 通过10种不同从头算水平对类反应中5个代表反应的反应势垒的计算发现, 用反应类等键反应方法和直接从头算方法获得的5 个代表反应的反应势垒最大绝对偏差的平均值分别为5.32 和16.16 kJ·mol^-1, 表明反应类等键反应方法计算的反应势垒对不同水平从头算方法的依赖性小, 可在较低从头算水平计算得到精确的反应势垒, 解决大分子体系反应势垒的精确计算问题. 此外应用反应类等键反应方法在BHandHLYP/cc-pVDZ 从头算水平计算了3 个代表反应的速率常数, 并与文献报道的实验值进行了比较, 其在500-2000 K温度区间内计算速率常数与实验速率常数中较大值与较小值的比值k_max/k_min的平均值为1.67, 最大值也仅有2.49. 表明应用反应类等键反应方法在较低从头算水平即可对同类反应的速率常数进行精确计算.最后在BHandHLYP/cc-pVDZ从头算水平用反应类等键反应方法计算了13个烷基自由基β位裂解反应的速率常数.     

CH3S自由基H迁移异构化及脱H2反应的直接动力学研究

采用密度泛函方法(MPW1PW91)在6-311G(d,p)基组水平上研究了CH₃S自由基H迁移反应CH₃S→CH₂SH (R1), 脱H₂反应CH₃S→HCS＋H₂ (R2)以及脱H₂产物HCS异构化反应HCS→CSH (R3)的微观动力学机理. 在QCISD(t)/6- 311＋＋G(d,p)//MPW1PW91/6-311G(d,p)＋ZPE水平上进行了单点能校正. 利用经典过渡态理论(TST)与变分过渡态理论(CVT)分别计算了各反应在200～2000 K温度区间内的速率常数k^TST和k^CVT, 同时获得了经小曲率隧道效应模型(SCT)校正后的速率常数k^CVT/SCT. 结果表明, 反应 R1, R2 和R3的势垒△E^≠分别为160.69, 266.61和241.63 kJ/mol, R1为反应的主通道. 低温下CH₃S比CH₂SH稳定, 高温时CH₂SH比CH₃S更稳定. 另外, 速率常数计算结果显示, 量子力学隧道效应在低温段对速率常数的计算有显著影响, 而变分效应在计算温度段内对速率常数的影响可以忽略.     

Br+CH3S(O)CH3反应机理的直接动力学研究

采用直接动力学的方法，对多通道反应体系Br＋CH3S（O）CH3进行了理论研究．在BH＆H-LYP／6-311G（2d，2p）水平下获得了优化几何构型、频率及最小能量路径（MEP），能量信息的进一步确认在MC-QCISD（单点）水平下完成．利用正则变分过渡态理论，结合小曲率隧道效应校正（CVT／SCT）方法计算了该反应的两个可行的反应通道在200K～2000K温度范围内的速率常数．在整个反应区间内，生成HBr的反应通道与生成CHa的反应通道存在着竞争，前者是主反应通道，后者是次反应通道．变分效应和小曲率隧道效应对反应速率常数的计算影响都很小．理论计算得到的两个反应通道的反应速率常数与实验值符合得很好．     

Quasiclassical trajectory study of the reaction O(3P) + HI → OH + I

Three-dimensional quasiclassical trajectory calculations were carried out for the reaction of oxygen atoms O(³P) with hydrogen iodide molecules (HI and DI) for the temperature range 200–550 K, using a LEPS potential-energy surface. The calculated results include reaction cross sections, rate constants, kinetic isotope effects, the influence of vibrational and rotational excitation of the reactants on the dynamics, and the product energy partitioning and angular distribution. The calculated results are in good agreement with the available experimental results. The dynamics of the O + HI reaction is discussed in view of the associated mass combination H + LH′ (H and H′ are heavy atoms and L is a light atom), and in relation to earlier trajectory results for the reactions O + HCl and O + HBr.     

Reaction of vibrationally excited HBr and I

The rate of the reaction HBr(ν) + I → HI + Br increases by at least a factor of 10⁹ when HBr(ν=0) is excited to HBr(ν 2). The increase is observed when the reacting level is directly excited by sequential laser excitation or when it is populated by collisional excitation. Bromine isotopic enrichment in BrI, the product of a subsequent reaction, was observed after isotopically selective excitation.     

Vibrational excitation and relaxation of HBr(V = 2) state

Vibrational fluorescence from the V = 2 to the V = 1 state is observed following excitation by a pulsed HBr chemical laser. The time dependence of the fluorescence is used to determine the rate of near-resonant vibration-to-vibration energy transfer, HBr(V = 1) + HBr(V = 1) ? HBr(V = 2) + HBr(V = 0) + δE = 90 cm⁻¹. The cross section for this reacti     

Theoretical study on the rate constants for the C2H5 + HBr --> C2H6 + Br reaction

The reaction C(2)H(5) + HBr --> C(2)H(6) + Br has been theoretically studied over the temperature range from 200 to 1400 K. The electronic structure information is calculated at the BHLYP/6-311+G(d,p) and QCISD/6-31+G(d) levels. With the aid of intrinsic reaction coordinate theory, the minimum energy paths (MEPs) are obtained at the both levels, and the energies along the MEP are further refined by performing the single-point calculations at the PMP4(SDTQ)/6-311+G(3df,2p)//BHLYP and QCISD(T)/6-311++G(2df,2pd)//QCISD levels. The calculated ICVT/SCT rate constants are in good agreement with available experimental values, and the calculate results further indicate that the C(2)H(5) + HBr reaction has negative temperature dependence at T < 850 K, but clearly shows positive temperature dependence at T > 850 K. The current work predicts that the kinetic isotope effect for the title reaction is inverse in the temperature range from 200 to 482 K, i.e., k(HBr)/k(DBr) < 1.     

六氟化铀与卤化氢气体的反应动力学研究

研究了UF6+HX(HX=HCl, HBr和HI)反应动力学, 结果显示,UF6+HX反应速率随着HCl-HBr-HI次序增加, 在室温下它们的反应速率常数分别为2.32×10^-^6, 6.43×10^-^4, 5.89×10^-^3s^-^1.Pa^-^1。UF6+HCl和UF6+HBr反应的表观活化能分别为11.29和4.18kj/mol。以上反应速率依次增加, 表出活化能依次减小的趋向与HX的键能以HCl-HBr-HI次序减小相符合。     

Quantum Wave Packet Studies on F ＋ HBr Reaction

IntroductionA series of reactions of fluorine atoms with hydro-gen halidesF HCl HF Cl (1)(ΔH—00=-137·10 kJ/mol)F HBr HF Br (2)(ΔH—00=-202·73 kJ/mol)F HI HF I (3)(ΔH—00= -270·45 kJ/mol)belongs to the prototypical heavy-light-heavy reactionsa     

Kinetics of manganese(III) acetate in acetic acid: generation of Mn(III) with Co(III), Ce(IV), and dibromide radicals; reactions of Mn(III) with Mn(II), Co(II), hydrogen bromide,and alkali bromides

The reaction of cobalt(III) acetate with excess manganese(II) acetate in acetic acid occurs in two stages, since the two forms Co(IIIc) and Co(IIIs) are not rapidly equilibrated and thus react independently. The rate constants at 24.5 degrees C are kc = 37.1 +/- 0.6 L mol-1 s-1 and ks = 6.8 +/- 0.2 L mol-1 s-1 at 24.5 degrees C in glacial acetic acid. The Mn(III) produced forms a dinuclear complex with the excess of Mn(II). This was studied independently and is characterized by the rate constant (3.43 +/- 0.01) x 10(2) L mol-1 s-1 at 24.5 degrees C. A similar interaction between Mn(III) and Co(II) is substantially slower, with k = (3.73 +/- 0.05) x 10(-1) L mol-1 s-1 at 24.5 degrees C. Mn(II) is also oxidized by Ce(IV), according to the rate law -d[Ce(IV)]/dt = k[Mn(II)]2[Ce(IV)], where k = (6.0 +/- 0.2) x 10(4) L2 mol-2 s-1. The reaction between Mn(II) and HBr2., believed to be involved in the mechanism by which Mn(III) oxidizes HBr, was studied by laser photolysis; the rate constant is (1.48 +/- 0.04) x 10(8) L mol-1 s-1 at approximately 23 degrees C in HOAc. Oxidation of Co(II) by HBr2. has the rate constant (3.0 +/- 0.1) x 10(7) L mol-1 s-1. The oxidation of HBr by Mn(III) is second order with respect to [HBr]; k = (4.10 +/- 0.08) x 10(5) L2 mol-2 s-1 at 4.5 degrees C in 10% aqueous HOAc. Similar reactions with alkali metal bromides were studied; their rate constants are 17-23 times smaller. This noncomplementary reaction is believed to follow that rate law so that HBr2. and not Br. (higher in Gibbs energy by 0.3 V) can serve as the intermediate. The analysis of the reaction steps then requires that the oxidation of HBr2. to Br2 by Mn(III) be diffusion controlled, which is consistent with the driving force and seemingly minor reorganization.     

Quantum scattering calculation of the O(1D)+HBr reaction

Three-dimensional time-dependent quantum wave packet calculation for the O((1)D)+HBr reaction has been carried out using an accurate ab initio global potential energy surface [K. A. Peterson, J. Chem. Phys. 113, 4598 (2000)]. The calculations show that the initial state-selected reaction probabilities are dominated by resonance structures, and the lifetime of the resonance is generally in the subpicosecond time scale. The energy dependence of the reaction cross section is computed, which manifests still resonance structures, and is a decreasing function of the translational energy. The thermal rate constants are also computed, which are nearly independent on the temperature. The calculation results are discussed and compared to similar reaction with deep well.     

反应(Cl+HBr→HCl+Br和Cl+HBr→BrCl+H)机理和速率的密度泛函理论研究

用密度泛函理论(DFT)B3LYP方法,在6-311G**基组下,计算研究了反应Cl+HBr→HCl+Br和Cl+HBr→BrCl+H的机理,求得的各过渡态均通过振动分析加以确认.运用求得的反应活化能,以及不同温度下过渡态和反应络合物的配分函数,借助绝对反应速率理论求得50～1500K的反应速率常数.