Criegee中间体气相反应热力学的G2理论计算

Criegee中间体已被认为是大气中一些重要污染物的来源，是引发大量次级反应的关键物质，与光化学氧化剂、有机过氧化物的产生，以及与酸雨、大气光化学烟雾和森林衰退等许多环境问题有关[1-4]．但由于Criegee中间体寿命短，对其可能参与的一些大气化学反应进行实验研究有一定难     

几种含芯电子相关能修正的G2和G2(ACI)方法

针对冻结芯电子近似,在MP2/6-311G(d,p)级别上对G2、MP2/6-311G(d)和MP2/6-311G(d,p)级别上对G2(QCI)方法进一步考虑了芯电子相关能修正,尝试建立了G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)方法。G2-l test set 的反应能量计算结果表明,这些方法进一步减小了经验修正量;G2(QCI/ful)和G2(QCI/fu2)也比G2(QCI)的总体精度有所提高;但G2(fu2)在G2基础上,总体精度没有改善。G2(fu2)、G2(QCI/ful)和G2(QCI/fu2)计算G2-l test set反应能量的平均绝对偏差分别为5.11、4.74和4.81kJ mol-1,G2和G2(QCI)分别为5.09和4.97kJ mol-1.     

G3(QCI)模型化学方法

建立了非微扰外推模式下的几种G3(QCI)方法：G3(QCI/fu1)、G3(QCI/fu2)、G3(QCI/ful)//B3PW91和G3(QCI/fu2)//B3PW91.其中,电子能量用QCISD(T,FC)/G3large直接计算,芯电子相关能分别在MP2/6-31G(d)和MP2/6-31G(d,p)级别上计算,对125个G2-1 test set 的计算结果表明,总体精度与G3和G3 //B3LYP相当;平均绝对偏差分别为4.370、4.389、4.061和4.022kJ mol-1,相应G3和G3//B3LYP分别为4.27和4.05kJ mol-1.文章提出的方法排除了G3中外推办法的不确定因素,且更适用于非平衡几何构型体系能量的定量计算。     

气相反应76/70C_(70)=C_(76)(D_2)热力学函数的计算

采用统计热力学方法计算了气相C76（D2）的标准热力学函数，在此基础上计算了不同温度下气相反应76／70C70＝C76（D2）的热力学函数，讨论了C70与C76（D2）之间相互转化的热力学条件．结果表明，气相中温度低于536K时C70转化为C76（D2），温度高于536K时气相中C76（D2）转化为C70。     

合成聚甲醛二甲基醚反应热力学的理论计算

采用密度泛函理论(DFT)方法在B3LYP/6-31＋G(d,p)水平上对聚甲醛二甲基醚(PODE)系列化合物进行了全优化和振动分析计算, 获得了该系列化合物的最优构型及热力学函数值. 通过设计等键反应计算了PODE的生成热, 并进一步计算了生成PODE的反应平衡常数及转化率, 进而判断这些反应的热力学可行性.     

含芯电子相关能修正的G2理论——G2(ful)

A general method in considering the core electronic correlation energies has been proposed and introduced into the standard Gaussian-2 (G2)[7] theory by small post-Hartree-Fock calculations. In this paper an additional MP2(FC)/6-31G(d) calculation over the G2 procedures is employed and examined in modification in modification to the flaw of Frozen-Core (FC) approximation of G2 vai eq.:
ΔE(full)= E[MP2(full)/6-31G(d)]-E[MP2(FC)/6-31G(d)]
where the MP2(full)/6-31G(d) energy has been obtained in the molecular geometry optimizations. This energy, ΔE(full), is directly added into the total G2 energy of a molecule in facilitating the effect of core electronic correlations for each molecule in chemical reactions. It has been shown that the over-all average absolute deviation for the 125 reaction energies of the G2 test set (test set 1) is slightly reduced from 5.09 to 5.01 kJ, mol(-1) while for the 55 D0 values, which have been used for the derivation of the A coefficient of the empirical High-Level...更多-Correction (HLC), it is also reduced from 4.99 [for both G2 and G2(COMPLETE)[8]]to 4.77 kJ• mol(-1). In addition, larger errors (greater than ±8.4 kJ•mol(-1) for the D0 energies are improved, especially for the largest error of the D0 of SO2 This error is reduced from 21.3 to 15.4 kJ. mol(-1), in which the experimental geometry would further reduce it by 7.1kJ.mol(-1)[8]. Another improvement is the absolute value of the A coefficient in HLC being reduced from 4.81 for G2 to 4.34 milli-hartrees which is believed to be useful in isolating the relationship between the HLC and the FC approximation. Modifications to the original G2 from this work is denoted as G2(fu 1) and thus the G2 (fu 1) total energy for a molecule is
E[G2(fu 1)]= E[G2]+Δ E(full)h
with a new ΔE[HLC] =-0.19α- 4.34nβ milli-hartree.     

分子C_(60)CH_2(C_(2V))气相热力学性质的理论研究

自从富勒烯被发现并能常量制备以来,人们就开始了对Ｃ６０衍生物的研究．Ｃ６０ＣＨ２是Ｃ６０最简单的衍生物之一,Ｃ６０ＣＨ２有２种异构体,根据所属点群的对称性划分一种是属Ｃ２Ｖ群的Ｃ６０ＣＨ２（Ｃ２Ｖ）,另一种是属ＣＳ群的Ｃ６０ＣＨ２（ＣＳ）．文献［１］...     

气相反应C_(60)+O_3=C_(6O)(C_(2v))+O_2热力学函数的计算

计算了气相反应C60＋O3＝C6O（C2v）＋O2的热力学函数．得到了该反应Gibbs自由能的具体数值，结果表明在所研究的温度范围内Gibbs自由能为负值，从热力学角度来说，该反应可以自发进行,在计算该气相反应热力学函数的基础上，给出了气相C6O（C2v）的标准热力学函数     

气相反应84/70 C_(70)(D_(5h))=C_(84)(D_2)热力学函数的计算

计算了不同温度下气相反应84／70C70（D5h）＝C84（D2）的热力学函数，讨论了C70（D5h）与C84（D2）之间相互转化的热力学条件；结果表明，温度低于2392K时C84（D2）比C70（D5h）稳定，温度高于2392K时气相中C70（D5h）比C84（D2）稳定；同时给出了气相C84（D2）的标准热力学函数。     

H2NNO2裂解与重排反应的理论热力学动力学研究

硝胺化合物的N—N键断裂和硝基-亚硝基重排(>N—NO_2→>N—ONO)是一类重要的化学反应。最近Golden等重新测定了DMNA[(CH_3)_2NNO_22]消失的速度常数,认为其分解应包括N—N键断裂和硝基-亚硝基重排后的再分解等过程,并得到分子束实验的确认,但理论研究尚不多见。Melius和McKee等都曾对该类体系进行过量化计算,但结果并不令人满意。Saxon等取其模型体系H_2NNO_2进行量化计算,似可定性说明其断裂、重排     

Reactions of Criegee Intermediates are Enhanced by Hydrogen-Atom Relay Through Molecular Design

We report a type of highly efficient double hydrogen atom transfer (DHAT) reaction. The reactivities of 3-aminopropanol and 2-aminoethanol towards Criegee intermediates (syn- and anti-CH₃CHOO) were found to be much higher than those of n-propanol and propylamine. Quantum chemistry calculation has confirmed that the main mechanism of these very rapid reactions is DHAT, in which the nucleophilic attack of the NH₂ group is catalyzed by the OH group which acts as a bridge of HAT. Typical gas-phase DHAT reactions are termolecular reactions involving two hydrogen bonding molecules; these reactions are typically slow due to the substantial entropy reduction of bringing three molecules together. Putting the reactive and catalytic groups in one molecule circumvents the problem of entropy reduction and allows us to observe the DHAT reactions even at low reactant concentrations. This idea can be applied to improve theoretical predictions for atmospherically relevant DHAT reactions.     

Kinetics and Thermodynamics of Reactions Involving Criegee Intermediates: An Assessment of Density Functional Theory and Ab Initio Methods Through Comparison with CCSDT(Q)/CBS Data

Reactions involving Criegee intermediates (CIs, R₁R₂COO) are important in atmospheric ozonolysis models. In recent years, density functional theory (DFT) and CCSD(T)-based ab initio methods are increasingly being used for modeling reaction profiles involving CIs. We obtain highly accurate CCSDT(Q)/CBS reaction energies and barrier heights for ring-closing reactions involving atmospherically important CIs (R₁/R₂ = H, Me, OH, OMe, F, CN, cyclopropene, ethylene, acetaldehyde, and acrolein). We use this benchmark data to evaluate the performance of DFT, double-hybrid DFT (DHDFT), and ab initio methods for the kinetics and thermodynamics of these reactions. We find that reaction energies are more challenging for approximate theoretical procedures than barrier heights. Overall, taking both reaction energies and barrier heights into account, only one of the 58 considered DFT methods (the meta-GGA MN12-L) attains near chemical accuracy, with root-mean-square deviations (RMSDs) of 3.5 (barrier heights) and 4.7 (reaction energies) kJ mol⁻¹. Therefore, MN12-L is recommended for investigations where CCSD(T)-based methods are not computationally feasible. For reaction barrier heights performance does not strictly follow Jacob's Ladder, for example, DHDFT methods do not perform better than conventional DFT methods. Of the ab initio methods, the cost-effective CCSD(T)/CBS(MP2) approach gives the best performance for both reaction energies and barrier heights, with RMSDs of 1.7 and 1.4 kJ mol⁻¹, respectively. All the considered Gaussian-n methods show good performance with RMSDs below the threshold of chemical accuracy for both reaction energies and barrier heights, where G4(MP2) shows the best overall performance with RMSDs of 2.9 and 1.5 kJ mol⁻¹, respectively. © 2019 Wiley Periodicals, Inc.     

Temperature-Dependence of the Rates of Reaction of Trifluoroacetic Acid with Criegee Intermediates

The rate coefficients for gas-phase reaction of trifluoroacetic acid (TFA) with two Criegee intermediates, formaldehyde oxide and acetone oxide, decrease with increasing temperature in the range 240–340 K. The rate coefficients k(CH₂OO + CF₃COOH)=(3.4±0.3)×10⁻¹⁰ cm³ s⁻¹ and k((CH₃)₂COO + CF₃COOH)=(6.1±0.2)×10⁻¹⁰ cm³ s⁻¹ at 294 K exceed estimates for collision-limited values, suggesting rate enhancement by capture mechanisms because of the large permanent dipole moments of the two reactants. The observed temperature dependence is attributed to competitive stabilization of a pre-reactive complex. Fits to a model incorporating this complex formation give k [cm³ s⁻¹]=(3.8±2.6)×10⁻¹⁸ T² exp((1620±180)/T) + 2.5×10⁻¹⁰ and k [cm³ s⁻¹]=(4.9±4.1)×10⁻¹⁸ T² exp((1620±230)/T) + 5.2×10⁻¹⁰ for the CH₂OO + CF₃COOH and (CH₃)₂COO + CF₃COOH reactions, respectively. The consequences are explored for removal of TFA from the atmosphere by reaction with biogenic Criegee intermediates.     

量子化学的Gaussian－2理论及其应用与化合物的标准生成焓预测

本文较为全面地综述了Ｇａｕｓｓｉａｎ－１，Ｇａｕｓｓｉａｎ－２（简称Ｇ１，Ｇ２）理论以及简化的Ｇ２（ＭＰ２），Ｇ２（ＭＰ３）理论，将其主要结果进行了比较分析。关于Ｇ２理论的应用，除了较为详细地综述了几年来理论在重现实验数据、评价实验数据、预测实验数据及研究化学反应途径等方面的应用外，还结合我们近期研究结果的主要结论讨论了该理论在研究等电子－等自旋，价层等电－等旋，等旋及非等旋化学反应的能量计算中的应用情况，以及该理论在预测化合物的标准生成焓方面的应用情况。     

Infrared Detection of Criegee Intermediates Formed during the Ozonolysis of β‐Pinene and Their Reactivity towards Sulfur Dioxide

Recently, direct kinetic experiments have shown that the oxidation of sulfur dioxide to sulfur trioxide by reaction with stabilized Criegee intermediates (CIs) is an important source of sulfuric acid in the atmosphere. So far, only small CIs, generated in photolysis experiments, have been directly detected. Herein, it is shown that large, stabilized CIs can be detected in the gas phase by FTIR spectroscopy during the ozonolysis of β‐pinene. Their transient absorption bands between 930 and 830 cm^?1 appear only in the initial phase of the ozonolysis reaction when the scavenging of stabilized CIs by the reaction products is slow. The large CIs react with sulfur dioxide to give sulfur trioxide and nopinone with a yield exceeding 80 %. Reactant consumption and product formation in time‐resolved β‐pinene ozonolysis experiments in the presence of sulfur dioxide have been kinetically modeled. The results suggest a fast reaction of sulfur dioxide with CIs arising from β‐pinene ozonolysis.     

Rate Coefficients of C1 and C2 Criegee Intermediate Reactions with Formic and Acetic Acid Near the Collision Limit: Direct Kinetics Measurements and Atmospheric Implications

Rate coefficients are directly determined for the reactions of the Criegee intermediates (CI) CH₂OO and CH₃CHOO with the two simplest carboxylic acids, formic acid (HCOOH) and acetic acid (CH₃COOH), employing two complementary techniques: multiplexed photoionization mass spectrometry and cavity‐enhanced broadband ultraviolet absorption spectroscopy. The measured rate coefficients are in excess of 1×10^?10 cm³ s^?1, several orders of magnitude larger than those suggested from many previous alkene ozonolysis experiments and assumed in atmospheric modeling studies. These results suggest that the reaction with carboxylic acids is a substantially more important loss process for CIs than is presently assumed. Implementing these rate coefficients in global atmospheric models shows that reactions between CI and organic acids make a substantial contribution to removal of these acids in terrestrial equatorial areas and in other regions where high CI concentrations occur such as high northern latitudes, and implies that sources of acids in these areas are larger than previously recognized.