苯和苯胺类硝基衍生物热解机理和撞击感度的理论研究

在DFT-B3LYP/6-31G*水平获得苯和苯胺类硝基衍生物的全优化分子几何和电子结构.通过非限制性(U)B3LYP/6-31G*计算求得标题物各化学键离解能(BDE).用UHF-PM3 MO方法求得引发键C-NO2键均裂反应的活化能(Ea).以静态指标(键集居数、前线轨道能级差和硝基上净电荷)和动态理论指标(BDE和Ea)阐明了热解引发机理,关联了实验撞击感度.运用SPSS程序关联静态和动态理论指标,表明它们均可以用作预示标题物的热解引发机理和撞击感度.     

高能化合物热解机理和撞击感度的理论研究-苯和苯胺类硝基衍生物

在DFT-B3LYP/6-31G*水平求得苯和苯胺类硝基衍生物的全优化分子几何和电子结构。通过非限制性 (U) B3LYP/6-31G*计算求得标题物各化学键离解能(BDE)。用UHF-PM3 MO方法求得引发键C-NO2键均裂反应的活化能(Ea)。以静态指标(键集居数、前线轨道能级差和硝基上净电荷)和动态理论指标(BDE和Ea) 阐明了热解引发机理,关联了实验撞击感度。运用SPSS程序关联静态和动态理论指标,表明它们可平行或等价地用作预示标题物的热解引发机理和撞击感度。     

环五甲撑五硝胺(CRX)结构和性质的DFT预示

用密度泛函理论(DFT)B3LYP方法,在6-31G*基组水平下,全优化计算了环五甲撑五硝胺(CRX)的分子几何和优化构型下的电子结构.环C-N键长为0.144～0.148 nm, N-NO2键长为0.139～0.142 nm; CRX的最高占有MO(HOMO)能级和最低未占MO(LUMO)能级之间的差值ΔEg(5.2054 eV)较大,预示CRX较稳定.基于简谐振动分析求得IR谱频率和强度.运用统计热力学方法,求得在200～1200 K的热力学性质C0p,m、 S0m和H0m.还运用Kamlet公式预示了它的爆速和爆压分别为9169 m/s和37.88 GPa.     

TATB与二氟甲烷以及与聚偏二氟乙烯的分子间相互作用

动用密度泛函理论(SFT)B3LYP方法,取3－21G*基组,求得TATB(1,3,5-三氨基-2,4,6-三硝基苯)与CH~2F~2混合体系的三种优化构型以Boys-Bernardi方案校正基组叠加误差求得结合能。在B3LYP/6----311G*//B3LYP/3---21G*水TATB与CH~2F~2间的最大结合能为4.62kJ·mol^-1,还用MO－PM3方法计算TATB与---（CF~2CH~2}－(N=1,2,3,4,5,)的混合体系,由色散校正电子相关近似地求得其结合能力。当n＝5时,求得TATB与－（CF~2CH~2）--~n的最大结合能约为52.97kJ·MOL^-1。此外,自然键轨道分析用于讨论TATB与CH~2F~2之间的电荷转移。     

F与CH~3F反应的可见化学发光

利用分子束装置研究了F与CH~3F反应可见光范围(450-900nm)的化学发光.观察到HCF(A~1A"-X2A')的七个振动带和HF^+电子基态振动广频跃迁的四个振动带和它们的强度随反应物流量的变化.求得HF分子的V'=4,5,6能级相对振动布居和V'=3的转动温度.分析表明两种光谱都是第二步反应(F+CH~2F)引起的,这步反应造成了HF高振动能级的统计性粒子分布和转动能级的玻尔兹曼分布.     

四Schiff碱(二苯并-18-冠-6)及其钾(I)/钴(II)配合物的合成和 性质

由二苯并-18-冠-6出发,合成了4',4',5',5'-四(2-羟基苯亚甲基亚氨基)二苯并-18-冠-6(L^1H~4)及其5位取代衍生物(取代基R=CH~3,OH,OCH~3,Cl,NO~2)L^2H~4～L^6H~4。它们依次与硝酸钾和醋酸钴反应,制得1:1:2的钾(I)/双钴(II)配合物LCo~2.2H~2O.KNO~3(L=L^5,L^6)或其某些二氧加合物LCo~2(2O~2).2H~2O.KNO~3(L=L^1～L^4)。考察了取代基R和冠醚环配合的钾离子对二氧加合物形成及稳定性的影响。结果表明,含吸电子基(R=Cl,NO~2)的钾(I)/双钴(II)配合物不能形成二氧加合物;冠环中的钾离子会导致二氧加合物中两个Co-O~2键热稳定性的差异。     

四Schiff碱(二苯并-18-冠-6)及其钾(I)/钴(II)配合物的合成和 性质

由二苯并-18-冠-6出发,合成了4',4',5',5'-四(2-羟基苯亚甲基亚氨基)二苯并-18-冠-6(L^1H~4)及其5位取代衍生物(取代基R=CH~3,OH,OCH~3,Cl,NO~2)L^2H~4～L^6H~4。它们依次与硝酸钾和醋酸钴反应,制得1:1:2的钾(I)/双钴(II)配合物LCo~2.2H~2O.KNO~3(L=L^5,L^6)或其某些二氧加合物LCo~2(2O~2).2H~2O.KNO~3(L=L^1～L^4)。考察了取代基R和冠醚环配合的钾离子对二氧加合物形成及稳定性的影响。结果表明,含吸电子基(R=Cl,NO~2)的钾(I)/双钴(II)配合物不能形成二氧加合物;冠环中的钾离子会导致二氧加合物中两个Co-O~2键热稳定性的差异。     

ε-六硝基六氮杂异伍兹烷（CL-20）热解机理的理论研究

运用量子化学中非限制性Hartree-Fock自洽场(UHF-SCF)PM3分子轨道(MO)方法,计算研究六硝基六氮杂异伍兹烷(HNIW或CL-20)的最稳定ε晶型化合物的气相热解引发反应.求得可能的四种不同热解反应通道的过渡态、活化能和位能曲线,发现其热解引发步骤为五元环上侧链N—NO2键的均裂.在过渡态附近相关原子电荷发生突变.     

四氢叶酸辅酶结构和性能的模拟及取代一碳单元转移反应的研究

本工作模拟了四氢叶酸辅酶的结构和反应性能, 合成了模型化合物碘化1, 2-二甲基-3-对甲氧苯磺酰基咪唑啉, 研究了模型化合物与单官能团亲核体、双官能团亲核体相作用, 以甲酸、甲醛氧化态转移取代一碳单元[≡C-CH~3, =C(CH~3)CH~2NO~2]的反应, 部分反应生成了咔啉类生物碱衍生物和其它杂环类化合物。     

ε-六硝基六氮杂异伍兹烷(CL-20)热解机理的理论研究

运用量子化学中非限制性Hartree-Fock自洽场(UHF-SCF) PM3分子轨道(MO)方法, 计算研究六硝基六氮杂异伍兹烷(HNIW或CL-20)的最稳定ε晶型化合物的气相热解引发反应. 求得可能的四种不同热解反应通道的过渡态、活化能和位能曲线, 发现其热解引发步骤为五元环上侧链N—NO₂键的均裂. 在过渡态附近相关原子电荷发生突变.     

Proton affinity of methyl nitrite and methyl peroxynitrite: implications for measuring branching ratios of alkyl nitrates and nitrites

Geometry optimizations for methyl nitrite and methyl peroxynitrite, along with various protonated isomers for each, have been investigated using ab initio and density functional methods. The lowest energy structure for protonated methyl nitrite is a complex between CH3OH and NO(+). For methyl peroxynitrite, the lowest energy protonated structure is a complex between CH3OOH and NO(+). Their respective proton affinities are estimated to be 195.2 and 195.8 kcal/mol at the QCISD(T)/6-311++G(3df,3pd) level of theory. The results, compared with past studies, suggest an alternative method for directly measuring branching ratios for production of alkyl nitrates and nitrites.     

Application of ab initio molecular dynamics for a priori elucidation of the mechanism in unimolecular decomposition: the case of 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO).

We have tested a new and general approach for the theoretical study of unimolecular decomposition. By combining the power of the ab initio molecular dynamics (MD) and ab initio molecular orbital (MO) methods, our approach requires no prior experimental knowledge or intuitive assumptions about the decomposition. Instead, the reaction channels are first sampled theoretically by simulating a molecule at high temperature in a number of trajectories, using the density functional theory (DFT) based ab initio MD method with a planewave basis set and pseudopotentials. Each type of these channels is then further examined by well-established ab initio MO method to locate the energy barrier and transition structure and to verify the ab initio MD results. The power of such an approach is demonstrated in a case study for the complicated unimolecular thermal decomposition of NTO (5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one), with several interesting new features uncovered. The C-NO2 homolysis is indeed the dominant channel at high temperature, while the departing NO2 could capture a H atom from the NTO ring to form HONO, by either a concerted bond breaking mechanism or by a bimolecular reaction between the NO2 group and the triazol ring. At lower temperature, the dissociation channels initiated by hydrogen migrations should be activated first. The channel with hydrogen migration followed by ring opening and then by HONO loss has an energy barrier of 38.0 kcal/mol at the rate-determining step, being the lowest among all the investigated dissociation paths and much lower than previously thought. The energy barrier for nitro-nitrite rearrangement is lower than that for the C-NO2 homolysis but makes only a minor contribution due to the entropy factor. And the NTO ring could rupture in the two C-N bonds connected to the carbonyl carbon, and the energy barriers for such processes are only 2-4 kcal/mol higher than that for the C-NO2 homolysis.     

Theoretical studies of the reactions of O(~3p) with halogenated methyl (Ⅰ)——Reaction mechanism of the O(~3p) CH_2Cl reaction

The reaction of O(~3P) with CH_2Cl radical has been studied using ab initio molecular orbital theory. G2 (MP2) method is used to calculate the geometrical parameters, vibrational frequencies and energies of various stationary points on the potential energy surface. The reaction mechanism is revealed. The addition of O(~3P) with CH_2Cl leads to the formation of an energy rich intermediate OCH_2Cl which can subsequently undergo decomposition or isomerization to the final products. The calculated heat of reaction for each channel is in agreement with the experimental value. The production of H CHClO and Cl CH_2O are predicted to be the major channels. The overall rate constants are calculated using transition state theory on the basis of ab initio data. The rate constant is pressure independent and exhibits negative temperature dependence at lower temperatures, in accordance with the experimental results.     

Theoretical Studies of the Reaction Mechanisms of CH3S＋NO2

The potential energy surface for the CH3S NO2 reaction has been studied using the ab initio G3(MP2) method. A variety of possible complexes and saddle points along the minimum energy reaction paths have been characterized at UMP2 (full)/6-31G(d) level. The calculations reveal dominating reaction mechanisms of the title reaction: CH3S NO2 firstly produce intermediate CH3SONO,then break up into CH3SO NO. The results are valuable to understand the atmospheric sulfur compounds oxidation mechanism.     

Kinetics and mechanism of the gas phase reaction of chlorine atoms with i-propanol

FTIR smog chamber techniques and ab initio calculations have been used to investigate the kinetics and mechanism of the reaction of Cl atoms with i-propanol in 700 Torr of N(2) at 296 K. The reaction is observed to proceed with a rate constant of k(1) = (8.28 +/- 0.97) x 10(-11) cm(3) molecule(-1) s(-1) and gives CH(3)C(OH)CH(3) and CH(3)CH(OH)CH(2) radicals in yields of 85 +/- 7 and 15 +/- 7%, respectively. Calculations indicate that abstraction of the secondary H can proceed through a lower energy pathway than the primary. Rapid decomposition of the chlorination product CH(3)CCl(OH)CH(3) complicates its direct detection, likely due to heterogeneous chemistry. IR spectra for the chlorides CH(3)CCl(OH)CH(3) and CH(3)CH(OH)CH(2)Cl were inferred experimentally and assignments confirmed via comparison with ab initio computed spectra.     

分子间相互作用的研究——-价轨道模型势从头算能量分解法

研究分子间相互作用是了解液体,固体性质和结构以及气体性质的关键,也是研究化学和生物化学催化机制及化学反应途径的重要方面.因此,近几年来这个领域的理论和实验研究引起了人们广泛的兴趣并取得了长足的进步.特别值得指出的是Morokuma等提出的基于单行列式从头算的能量分解法,较好地解决了很多体系中分子间相互作用的本质问题,受到了理论化学界的普遍重视.但是这种方法很费计算机时间,对于较大的体系,特别是含有重原子的体系,应用受到了限制.因此简化这种方法,使它能够比较容     

氧原子和甲基自由基反应机理的理论研究

用分子轨道从头算和密度泛函理论（DFT）中的B3LYP方法以及适中基组6-311+G(2df,2p)对氧原子与甲基CH3反应进行了系统的研究。计算给出了反应通道上各驻点物种的构型参数、振动频率和能量。结果表明： CH2OH比CH3O稳定,能量约低26.63 kJ/mol,且生成氢和甲醛为其最主要反应通道。     

Ab initio potential energy surface, variational transition state theory, and quasiclassical trajectory studies of the F+CH4-->HF+CH3 reaction

In this work we present a study of the F+CH(4)-->HF+CH(3) reaction (DeltaHdegrees(298 K)=-32.0 kcal mol(-1)) using different methods of the chemical reaction theory. The ground potential energy surface (PES) is characterized using several ab initio methods. Full-dimensional rate constants have been calculated employing the variational transition state theory and using directly ab initio data. A triatomic analytical representation of the ground PES was derived from ab initio points calculated at the second- and fourth-order M?ller-Plesset levels with the 6-311+G(2df,2pd) basis set, assuming the CH(3) fragment to be a 15 a.m.u. pseudoatom in the fitting process. This is suggested from experiments that indicate that the methyl group is uncoupled to the reaction coordinate. A dynamics study by means of the quasiclassical trajectory (QCT) method and employing this analytical surface was also carried out. The experimental data available on the HF internal states distributions are reproduced by the QCT results. Very recent experimental information about the reaction stereodynamics is also borne out by our QCT calculations. Comparisons with the benchmark F+H(2) and analogous Cl+CH(4) reactions are established throughout.     

Endgroup-assisted siloxane bond cleavage in the gas phase

Unimolecular dissociation of H(2)N(CH(2))(3)SiOSi(CH(2))(3)NH(3)(+) generates SiC(5)H(16)NO(+) and SiC(5)H(14)N(+). The formation of SiC(5)H(16)NO(+) involves dissociation of a Si[bond]O bond and formation of an O[bond]H bond through rearrangement. The fragmentation mechanism was investigated utilizing ab initio calculations and Fourier transform ion cyclotron resonance (FTICR) mass spectrometry in combination with hydrogen/deuterium (H/D) exchange reactions. Sustained off-resonance irradiation collision-induced dissociation (SORI-CID) studies of the fully deuterated ion D(2)N(CH(2))(3)SiOSi(CH(2))(3)ND(3)(+) provided convincing evidence for a backbiting mechanism which involves hydrogen transfer from the terminal amine group to the oxygen to form a silanol-containing species. Theoretical calculations indicated decomposition of H(2)N(CH(2))(3)SiOSi(CH(2))(3)NH(3)(+) through a backbiting mechanism is the lowest energy decomposition channel, compared with other alternative routes. Two mechanisms were proposed for the fragmentation process which leads to the siloxane bond cleavage and the SORI-CID results of partially deuterated precursor ions suggest both mechanisms should be operative. Rearrangement to yield a silanol-containing product ion requires end groups possessing a labile hydrogen atom. Decomposition of disiloxane ions with end groups lacking labile hydrogen atoms yielded product ions from direct bond cleavages.     

Vibrational spectroscopy of nitroalkane chains using electron autodetachment and ar predissociation

If the binding energy of an excess electron is lower than some of the vibrational levels of its host anion, vibrational excitation can lead to autodetachment. We use excitation of CH stretching modes in nitroalkane anions (2700-3000 cm(-1)), where the excess electron is localized predominantly on the NO2 group. We present data on nitroalkane anions of various chain lengths, showing that this technique is a valid approach to the vibrational spectroscopy of such systems extending to nitroalkane anions at least the size of nitropentane. We compare spectra taken by using vibrational autodetachment with spectra obtained by monitoring Ar evaporation from Ar solvated nitroalkane anions. The spectra of nitromethane and nitroethane are assigned on the basis of ab initio calculations with a detailed analysis of Fermi resonances of CH stretching fundamentals with overtones and combination bands of HCH bending modes.