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1.
采用密度泛函方法(MPW1PW91)在6-311G(d,p)基组水平上研究了CH 3S自由基H迁移反应CH 3S→CH 2SH (R1), 脱H 2反应CH 3S→HCS+H 2 (R2)以及脱H 2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 kTST和 kCVT, 同时获得了经小曲率隧道效应模型(SCT)校正后的速率常数 kCVT/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CH 3S比CH 2SH稳定, 高温时CH 2SH比CH 3S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. 相似文献
2.
在G3XMP2//B3LYP/6-311+G(3df,2p)水平上对CH 3SO 3裂解反应的机理进行了研究, 获得了6 条通道(10 条路径), 并构建了其势能剖面. 同时采用单分子反应理论计算了各个通道在温度200-3000 K区间的速率常数. 研究结果表明, 在计算温度范围内, CH 3SO 3裂解反应的主产物为P1(CH 3+SO 3), 产物P2(CH 3O+SO 2)和P3(HCHO+HOSO)仅在温度大于3000 K时对总产物有贡献, 而产物P4(CHSO 2+H 2O), P5(CH 2SO 3+H)和P6(CHSO 3+H 2)贡献相对较少. 将裂解反应总的速率常数拟合为k total=1.40×10 12T 0.15exp(7831.58/T). 此外, 根据统计热力学原理, 预测了所有物种的生成焓(D fH Θ298 K, D fH 0 K), 熵(S Θ298 K)和热容(C p, 298-2000 K), 计算的结果与实验值较接近. 相似文献
3.
利用密度泛函理论直接动力学方法研究了反应CH 3OCF 2CF 2OCH 3+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CH 3OCF 2CF 2OCH 3两个稳定构象(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). 相似文献
4.
采用双水平直接动力学方法对C 2H 3与CH 3F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. 相似文献
5.
应用量子化学从头算和密度泛函理论(DFT)对CH 3S与HCS双自由基单重态反应进行了研究. 在MPW1PW91/ 6-311G(d,p)水平上优化了反应通道上各驻点(反应物、中间体、过渡态和产物)的几何构型, 用内禀反应坐标(IRC)计算和频率分析方法对过渡态进行了验证. 在QCISD(t)/6-311++G(d,p)水平上计算各物种的单点能, 并对总能量进行了零点能校正. 研究结果表明, CH 3S与HCS反应为多通道反应, 有4条可能的反应通道, 反应物首先通过S…S弱相互作用形成具有竞争反应机理的五元环硫-硫偶合中间体a和链状硫-硫偶合中间体c, 再由此经过氢迁移、离解、异构化等不同机理得到主要产物P1 (2CH 2S), 次要产物P2 (CH 3SH+CS), P3 (CH 4+CS 2)和P4 [CH 2(SH)CSH]. 根据势能面分析, 所有反应均为放热反应, 生成P1的反应热为-165.55 kJ•mol -1. 通道R→a→TSa/b→b→P1为标题反应的主通道, 其速控步骤a→TSa/b→b在200~2000 K温度区间内的速率常数可以表示为k 1CVT/SCT=1.75×10 10T 0.65exp(-907.6/T) s -1. P3及P4的生成需要越过很高的活化能垒, 是动力学禁阻步骤, 但在反应体系中加入合适催化剂, 改变其反应机理, 有可能使生成CH 2(SH)CSH, CH 4及CS 2的反应易于进行. 相似文献
6.
用密度泛函理论(DFT)的B3LYP方法,在6-311G、6-311+G( d)、6-311++G( d, p) 基组水平上研究了CH 3CF 2O 2与HO 2自由基反应机理. 结果表明, CH3CF 2O 2与HO 2自由基反应存在两条可行的通道. 通道CH3CF 2O 2+HO 2→IM1→TS1→CH 3CF 2OOH+O 2的活化能为77.21 kJ•mol -1,活化能较低,为主要反应通道,其产物是O 2和CH 3CF 2OOH. 这与实验结果是一致的;而通道CH 3CF 2O 2+HO 2→IM2→TS2→IM3→TS3→IM4+IM5→IM4+TS4→IM4+OH+O 2→TS5+OH+O 2→CH 3+CF 2O+OH+O 2→CH 3OH+CF 2O+O 2的控制步骤活化能为93.42 kJ•mol -1,其产物是CH 3OH、CF 2O和O 2. 结果表明这条通道也能发生,这与前人的实验结果一致. 相似文献
7.
在6-311+G(2d,2p)水平下, 采用密度泛函理论(DFT)的B3LYP方法, 研究了Criegee 自由基CH 2O 2与H 2O的反应. 结果表明反应存在三个通道: CH 2O 2+H 2O®HOCH 2OOH (R1); CH 2O 2+H 2O®HCO+OH+H 2O (R2); CH 2O 2+H 2O®HCHO+H 2O 2 (R3), 各通道的势垒高度分别为43.35, 85.30和125.85 kJ/mol. 298 K下主反应通道(R1)的经典过渡态理论(TST)与变分过渡态理论(CVT)的速率常数 kTST与 kCVT均为2.47×10 -17 cm 3•molecule -1•s -1, 而经小曲率隧道效应模型(SCT)校正后的速率常数 kCVT/SCT为 5.22×10 -17 cm 3•molecule -1•s -1. 另外, 还给出了200~2000 K 温度范围内拟合得到的速率常数随温度变化的三参数Arrhenius方程. 相似文献
8.
用密度泛函(DFT)B3LYP/6-311++G**方法研究了氧化腈(RCNO, R=F, NO 2, OCH 3, OH, COOCH 3, CHO, CONH 2, H, CH 3)与丙炔的1,3-偶极环加成反应, 并且计算了不同温度下的反应速率常数, 讨论了氧化腈上不同取代基R的取代效应和温度对反应区域选择性的影响. 结果显示, 氧化腈与富电子亲偶极体——炔烃反应, 5-取代反应占优势; 氧化腈上取代基R为强吸电子基团时或在较高温度下, 有利于4-取代反应的进行. 相似文献
9.
在QCISD(T)/6-311+G(d,p)//B3LYP/6-311+G(3df,3pd)水平上, 对CH 3O与ClO双自由基反应进行了理论研究. 结果表明, 该反应共有三个反应通道, 产物分别为HOCl+CH 2O, CH 2O 2+HCl和CH 3Cl+O 2( 1Δ). 不论从动力学角度, 还是从热力学角度看, 形成产物HOCl+CH 2O的通道均是最有利的, 因此为主要反应通道, 这与实验观察到的结果是一致的. 相似文献
10.
利用密度泛函(DFT)和自然键轨道理论(NBO)及高级电子耦合簇[CCSD(T)]和电子密度拓扑(AIM)方法, 对单重态和三重态CH 2与CH 2CO反应的微观机理进行了研究. 在B3LYP/6-311+G(d,p)水平上优化了反应通道各驻点的几何构型. 在CCSD(T)/6-311+G(d,p)水平上计算了各物种的单点能量, 并对总能量进行了校正. 计算表明, 单重态CH 2与CH 2CO的C—H键可发生插入反应, 与C=C、C=O可发生加成反应, 存在三条反应通道, 产物为CO和C 2H 4, 从能量变化和反应速控步骤能垒两方面考虑, 反应II更容易发生. 对反应通道中的关键点进行了自然键轨道及电子密度拓扑分析. 三重态CH 2与CH 2CO的反应存在三条反应通道, 一条是与C-H键的插入反应, 另一条是三重态CH 2与C=C发生加成反应, 产物为CO和三重态C 2H 4, 通道II势垒较低, 更容易发生. 最后一条涉及双自由基的反应活化能最大, 最难发生. 相似文献
11.
采用CCSD(T)/6-311++G(3 df, 2 pd)//B3LYP/6-311+G(2 df, 2 p)双水平计算方法构建了HO 2+HS反应体系的单、三重态反应势能面,并对该反应主通道的速率常数进行了研究。研究结果表明,标题反应经历了八条反应通道,其中三重态反应通道R1是标题反应主通道。此通道包含路径Path 1 (R → 3IM1 → 3TS1 → P1( 3O 2+H 2S))和Path 1a (R → 3IM1a → 3TS1a → P1( 3O 2+H 2S))两条路径。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),分别计算了主路径Path 1和Path 1a在200-800 K温度范围内的速率常数 kTST、 kCVT和 kCVT/SCT,在此温度区间内路径Path 1和Path 1a具有负温度系数效应。速率常数计算结果显示,对主路径Path 1和Path 1a而言,变分效应在计算温度段内有一定影响,与此同时量子力学隧道效应在低温段有显著影响。路径Path 1和Path 1a的CVT/SCT速率常数的三参数表达式分别为 k1CVT/SCT(200-800 K) = 1.54×10 -5T-2.70exp(1154/ T) cm 3 ·molecule -1·s -1和 k1aCVT/SCT(200-800 K) = 5.82×10 -8T-1.84exp(1388/ T) cm 3·molecule -1·s -1。 相似文献
12.
The rate constants, k1 and k2 for the reactions of C 2F 5OC(O)H and n-C 3F 7OC(O)H with OH radicals were measured using an FT-IR technique at 253–328 K. k1 and k2 were determined as (9.24 ± 1.33) × 10 −13 exp[−(1230 ± 40)/ T] and (1.41 ± 0.26) × 10 −12 exp[−(1260 ± 50)/ T] cm 3 molecule −1 s −1. The random errors reported are ±2 σ, and potential systematic errors of 10% could add to the k1 and k2. The atmospheric lifetimes of C 2F 5OC(O)H and n-C 3F 7OC(O)H with respect to reaction with OH radicals were estimated at 3.6 and 2.6 years, respectively. 相似文献
13.
The kinetics of the association reaction of CF 3 with NO was studied as a function of temperature near the low-pressure limit, using pulsed laser photolysis and time-resolved mass spectrometry. CF 3 radicals were generated by photolysis of CF 3I at 248 nm and the kinetics was determined by monitoring the time-resolved formation of CF 3NO. The bimolecular rate constants were measured from 0.5 to 12 Torr, using nitrogen as the buffer gas. The results are in very good agreement with recent data published by Vakhtin and Petrov, obtained at room temperature in a higher pressure range and, therefore, the two studies are quite complementary. A RRKM model was developed for fitting all the data, including those of Vakhtin and Petrov and for extrapolating the experimental results to the low- and high-pressure limits. The rate expressions obtained are the following: k1(0) = (3.2 ± 0.8) × 10 −29 ( T/298) −(3.4±0.6) cm 6 molecule −2 s −1 for nitrogen used as the bath gas and k1(∞) = (2.0 ± 0.4) × 10 −11 ( T/298) (0±1) cm 3 molecule −1 s −1. RRKM calculations also help to understand the differences in reactivity between CF 3 and other radicals, for the same association reaction with NO. 相似文献
14.
At 25°C, I = 1.0 M (CF 3SO 3−Li ++CF 3SO 3H), [H +] = 0.034–0.274 M and λ = 453 nm, the rate equation for the oxidation of Ti(H 2O), 63+ by bromine was found to be: −d/[Br 2] T/d t= kK/[Br 2][Ti III]/[H +]+ K+ kK/[Br 3−][Ti III]/[H ++ K, where k = 9.2 × 10 −3 M −1 s −1 and K = 4.5 × 10 −3 M. At [H +] = 1.0 M, [Br −] = 0.05–0.4 M, the apparent second-order rate constant decreases as [Br −] increases. The pH-dependence of the oxidation of TiIII-edta by bromine is interpreted in terms of the change in identity of the TiIII-edta species as the pH of the reaction medium changes. The second-order rate constants were fitted using a non-linear least-square computer program with (1/k0edta)2 weighting into an equation of the form: k0edta =k1+k2K1[H+]−1+k3K1K2[H+]−2/1+K1[H+[H+−1+K1K2[H+]−2, with K1 and K2 fixed as earlier determined at 9.55 × 10−3 and 2.29 × 10−9 M, respectively, for the oxidation of bromine. k1=k2=(3.1±0.32)×103M−1s−1 k3=(2.3±0.45)×106N−1s−1. It is proposed that these electron transfer reactions proceed by univalent changes with the production of Br2.− as a transient intermediate. An outer-sphere mechanism is proposed for these reactions. The homonuclear exchange rate for TiIII-edta+TiIV-edta is estimated at 32 M−1 s−1. 相似文献
15.
利用瞬态吸收光谱技术进行了有氧、无氧条件下氯苯与亚硝酸水溶液的交叉反应机理研究,初步考察了这些瞬态物种的生长与衰减等行为, 并对其光解产物进行了GC/MS分析.研究表明,HNO 2在355 nm紫外光的照射下可产生•OH自由基, •OH和氯苯反应生成C 6H 5Cl•••OH,反应速率常数为(6.6~7.0)×10 9 L•mol -1•s -1; 在有氧条件下C 6H 5Cl•••OH可氧化为C 6H 5Cl•••OHO2, 反应速率常数为(1.6 ± 0.2)×109 L•mol -1•s -1,然后进一步分解; C 6H 5Cl•••OH衰减或与亚硝酸等作用可形成多种含硝基的化合物或醌类物质. 相似文献
16.
The second-order rate constants of gas-phase Lu( 2D 3/2) with O 2, N 2O and CO 2 from 348 to 573 K are reported. In all cases, the reactions are relatively fast with small barriers. The disappearance rates are independent of total pressure indicating bimolecular abstraction processes. The bimolecular rate constants (in molecule −1 cm 3 s −1) are described in Arrhenius form by k(O 2)=(2.3±0.4)×10 −10exp(−3.1±0.7 kJmol −1/ RT), k(N 2O)=(2.2±0.4)×10 −10exp(−7.1±0.8 kJmol −1/ RT), k(CO 2)=(2.0±0.6)×10 −10exp(−7.6±1.3 kJmol −1/ RT), where the uncertainties are ±2σ. 相似文献
17.
用非等温TG-DTA技术, 在5.0、10.0、15.0和20.0 K•min -1线性升温条件下, 研究聚羟基丁酸-戊酸(PHBV)的热分解反应动力学. 结果表明, 分解过程分三个阶段:分解初期、分解中期和分解后期. 分解初期的机理函数为Avrami-Erofeev方程(n=1/2), 对应随机成核和随后生长机理, 表观活化能E a( β→0)为69.44 kJ•mol -1, 指前因子A( β→0)为106.27 s -1;分解中期的机理函数为Avrami-Erofeev方程(n =2/5), 对应随机成核和随后生长机理, 表观活化能Ea( β→0)为117.64 kJ•mol -1, 指前因子A( β→0)为10 11.48 s -1;分解后期的机理函数为Mampel Power法则(n=1/3), 对应机理为幂函数法则, 表观活化能Ea( β→0)为116.64 kJ•mol -1, 指前因子A( β→0)为10 8.68 s -1. 相似文献
18.
The rate coefficients of the reactions: (1) CN + H 2CO → products and (2) NCO + H 2CO → products in the temperature range 294–769 K have been determined by means of the laser photolysis-laser induced fluorescence technique. Our measurements show that reaction (1) is rapid: k1(294 K) = (1.64 ± 0.25) x 10 −11 cm 3 molecule −1 s −1; the Arrhenius relation was determined as k1 = (6.7 ± 1.0) x 10 −11 exp[(−412 ± 20)/T] cm 3 molecule −1 s −1. Reaction (2) is approximately a tenth as rapid as reaction (1) and the temperature dependence of k2 does not conform to the Arrhenius form: k2 = 4.62 x 10 −17T1.71 exp(198/ T) cm 3 molecule −1 s −1. Our values are in reasonable agreement with the only reported measurement of k1; the rate coefficients for reaction (2) have not been previously reported. 相似文献
19.
The thermal behavior and non-isothermal decomposition kinetics of 1-amino-1-hydrazino-2,2-dinitro- ethylene potassium salt[K(AHDNE)] were studied under the non-isothermal conditions by different scanning calorimeter(DSC) method. The thermal behavior of K(AHDNE) presents three exothermic decomposition processes. The kinetic equation of the first thermal decomposition reaction obtained is d α/d T=(10 19.63/ β)3(1- α)[-ln(1- α)] 2/3exp(-1.862×
10 5/RT). The self-accelerating decomposition temperature( TSADT) and critical temperature of thermal explosion( Tb) of K(AHDNE) are 162.5 and 171.4 ℃, respectively. K(AHDNE) has higher thermal stability than AHDNE. 相似文献
20.
Deuterium NMR spectra of perdeuteriated 1,4-dimethylcyclohexane- d16 and 1,1-dimethylcyclohexane- d16 dissolved in the nematic solvent ZLI 2452 are reported for the temperature range -40 to +80°C. Between -30 and +60°C the spectra exhibit characteristic exchange broadening and coalescence due to the ring inversion process. In the extreme slow exchange regime, peak assignment and determination of relative signs of the deuterium quadrupole interactions were made using 2D exchange spectroscopy and structural parameters derived from molecular mechanics calculations. In the intermediate temperature range the lineshapes were interpreted quantitatively in terms of the ring interconversion kinetics yielding the kinetic equations, k = 1.38 × 10 13 exp (-45.2/ RT)s -1 for 1,4-dimethylcyclohexane, and k = 4.05 × 10 13 exp (-49.0/ RT)s -1 for 1,1-dimethylcyclohexane, where R is in kJ mol -1. The complete ordering matrix of both compounds was determined over the whole temperature range of the measurements. 相似文献
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