HS+HO2气相反应机理及主通道速率常数的理论研究

采用CCSD(T)/6-311++G(3df, 2pd)//B3LYP/6-311+G(2df, 2p)双水平计算方法构建了HO₂+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(³O₂+H₂S))和Path 1a (R → ³IM1a → ³TS1a → P1(³O₂+H₂S))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k^TST、k^CVT和k^CVT/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k₁^CVT/SCT(200-800 K) = 1.54×10^-5T^-2.70exp(1154/T) cm³ ·molecule^-1·s^-1和k_1a^CVT/SCT(200-800 K) = 5.82×10^-8T^-1.84exp(1388/T) cm³·molecule^-1·s^-1。     

CF3CH2CH3+OH的反应机理及动力学性质的理论研究

采用密度泛函理论BB1K/6-31+G(d,p)计算了反应CF₃CH₂CH₃+OH各反应通道上驻点的稳定结构和振动频率, 并分别在BMC-CCSD, MC-QCISD和G3(MP2)水平上进行了单点能校正. 运用变分过渡态理论, 在BMC-CCSD//BB1K, MC-QCISD//BB1K, G3(MP2)//BB1K以及BB1K水平上计算了各反应通道的速率常数, 讨论了-CH₂和-CH₃基团上H提取通道对总反应的贡献, 并与已有实验和理论结果进行了对比. 计算结果表明, BMC-CCSD水平上的速率常数与实验测量值符合得很好, 进而给出了该水平上反应在200~1000 K温度范围内速率常数k(cm³?molecule^-1?s^-1)的三参数表达式: k=1.90×10^-21T^3.21exp(-292.62/T).     

Criegee中间体CH3CHOO与H2O反应机理及酸催化效应

采用CCSD（T）//B3LYP/6-311+G（d,p）方法研究了H₂O及甲酸等6种有机酸对CH₃CHOO与H₂O加成反应的催化作用。结果表明,非催化反应存在双质子迁移和加成反应2条通道,其中加成反应为优势通道。其加成机理为H₂O中OH加到CH₃CHOO的α-C上,同时H₂O中另一个H迁移到CH₃CHOO的端O上。催化剂H₂O及有机酸以氢键复合物的形式参与反应促进了H质子转移,可降低基元反应能垒和表观活化能,且催化效应与有机酸的强度成正比。例如,当分别用H₂O（pK_a=15.7）、甲酸（pK_a=3.75）和草酸（pK_a=1.23）催化时,生成syn-HAHP的基元反应能垒由非催化的69.12 kJ·mol^-1分别降至40.78、18.88和10.61 kJ·mol^-1。非催化反应具有正的表观活化能,而所有催化反应则均具有负的表观活化能。     

新型含硅表面活性剂的合成及性能研究

含有双胺基的三硅氧烷中的伯胺基与D-葡萄糖酸-δ-内酯进行酰胺化,仲胺基与低聚乙二醇甲醚缩水甘油醚、二缩水甘油醚进行烷基化,制备了新型含硅表面活性剂Me₃SiOSiMeR¹OSiMe₃ [R¹=(CH₂)₃NR²(CH₂)₂NHCO(CHOH)₄CH₂OH; R²=H, CH₂CH(OH)CH₂O(CH₂CH₂O)_xCH₃, x=1, 2, 3] (1a, 2a～2c)和(CH₂OCH₂)_y(Me₃SiOSiMeR³OSiMe₃)₂ [R³=(CH₂)₃NR⁴～(CH₂)₂NHCO(CHOH)₄CH₂OH; R⁴=CH₂CH(OH)CH₂OCH₂, y=0, 1, 2] (3a～3c).这些化合物的结构用¹H, ¹³C核磁共振仪和元素分析仪进行鉴定.研究了这些新型含硅表面活性剂的界面性能,在浓度分别为10^-4和10^-5 mol·L^-1时可以将水的表面张力降低至约21 mN·m^-1.     

NH3R++NHR2(R=H,CH3)体系质子传递反应的从头算研究

用从头计算法在HF/6-31G^*基组水平上研究了NH₄⁺+NH₃→NH₃+NH₄⁺,NH₄⁺+NH₂CH₃→NH₃+NH₃CH₃⁺,NH₄⁺+NH(CH₃)₂→NH₃+NH₂(CH₃)₂⁺以及NH₃CH₃⁺+NH₂CH₃→NH₂CH₃+NH₃CH₃⁺等4个体系的质子传递反应的机理.结果表明:(1)上述质子传递反应均具有双阱型的势能面,质子沿N(1)、N(2)连线直接传递;(2)质子受体分子中的甲基对质子传递起促进作用,而质子给体离子中的甲基则阻碍质子的传递。     

黑果枸杞叶多糖LRLP3的结构、抗氧化活性及免疫活性

黑果枸杞叶经水提醇沉, 离子交换柱层析和凝胶柱层析分离纯化, 得到平均分子量为79400的均一多糖组分LRLP3. 对该多糖的理化性质、 结构、 抗氧化活性及免疫活性的研究结果表明, LRLP3为多分支结构, 主链为(1→3)βGalp, 大部分半乳糖6位存在分支; 支链由(1→6)βGalp, (1→4)βGalp, (1→3)βAraf, (1→3)αArap, (1→5)βAraf和(1→2,4)αRhap组成, 非还原末端由αAraf, βGalp和βGlcp组成. LRLP3具有较强的还原能力, 可显著清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基、 羟自由基和超氧阴离子自由基, 有效抑制Cu²⁺/H₂O₂诱导的蛋白氧化损伤和H₂O₂诱导的细胞氧化损伤. LRLP3在体外对未经诱导和经刀豆蛋白(ConA)或脂多糖(LPS)诱导的小鼠脾细胞增殖均有促进作用.     

F+CH2CO的反应机理和动力学研究

用G3(MP2)方法对F与CH₂CO的反应进行研究,揭示了该反应的加成-消除机理.F原子首先与CH₂CO作用形成富能的中间体CH₂FCO^*,此加成反应为无势垒过程.富能的CH₂FCO^*可进一步发生解离或异构化反应生成各种可能的产物.其中CO和CH₂F可能为反应的主要产物.根据从头算的结果,用RRKM-TST理论计算该反应的速率常数.总包反应速率常数与温度存在弱的依赖关系,与总压力无关.     

2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物的酸催化Smiles重排反应动力学

研究了酸催化下的2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物Smiles重排反应的动力学,考察了盐酸的初始浓度、溶剂、反应温度和取代基对反应速率的影响。结果表明,盐酸的初始浓度增加,重排反应速率加快;在单一溶剂中反应速率的顺序为:甲醇>乙醇>二甲基亚砜>乙腈,而在甲醇/水(1:1, V/V)的混合溶剂中反应速率明显增加,其表观反应速率常数(k_obs)值是甲醇溶剂中的5.27倍;在25-45 ℃温度范围内,各衍生物的反应速率随着温度的升高而加快,其活化能(73.99-76.92 kJ·mol^-1)、活化焓(71.57-74.38 kJ·mol^-1)及Gibbs自由能(81.51-85.77 kJ·mol^-1)数值相近,仅活化熵(-24.38 --47.11 J·K^-1·mol^-1)有一定的差别;取代基常数和表观速率常数之间呈现一定的线性关系,环上吸电子基团的存在有利于反应速率的提高;实验验证了反应机理的合理性。     

乙醇在Co(111)表面脱氢反应机理的第一性原理研究

采用密度泛函理论和周期平板模型相结合的方法针对Co（111）表面上乙醇脱氢反应的反应机理进行了细致的研究,同时,对反应过程中涉及到的各个物种在表面上不同吸附位（顶位（top）,桥位（bridge）,三重空穴位（fcc和hcp））的吸附模型进行了结构优化以及相关能量的计算,确定了各物种的最佳吸附位点.研究结果表明,CH₃CH₂OH在Co（111）表面的脱氢反应可具体描述为三条反应路径：反应路径I为CH₃CH₂OH逐步脱氢经由中间体CH₃CHO,最终生成CH₄和CO的反应;反应路径Ⅱ为CH₃CH₂OH脱氢产生的CH₃CH₂O基和CH₃CHO相互作用通过CH₃COOH分子最终生成CH₄和CO₂的反应;反应路径Ⅲ为CH₃CH₂O基和CH₃CO基作用生成CH₃COOC₂H₅的过程,其中,反应路径I为最优路径（CH₃CH₂OH→CH₃CH₂O→CH₃CHO→CH₃CO→CH₃+CO→CH₂→CH→CH₄+CO+C+H）,该反应路径中的CH₃CH₂O基脱氢生成CH₃CHO为速控步骤,反应能垒为1.61 eV.     

纳米尺寸氧化钇团簇阴离子与正丁烷反应的研究

在单一原子量分辨水平上研究纳米尺寸过渡金属氧化物团簇(M_xO_y^q)与小分子的反应不仅能够获得氧化物纳米颗粒的反应性随原子组成和尺寸连续变化的演变规律, 而且对认识其结构特征以及表面活性氧物种(如O^-•自由基)的产生机制等具有重要意义. 本工作分别采用耦合快速流动反应管和耦合四极质量过滤器-线形离子阱的两套反射式飞行时间质谱研究了不同“氧缺陷指数”(Δ)的氧化钇团簇Y_xO_y^- (x≤50,y≤76; Δ≡2y–1–3x, Δ=0~5)和掺杂氟(F)原子团簇Y _xO_yF^- [x≤49,y≤74; Δ≡(2y+1)–1–3x, Δ=1]与 n-C₄H₁₀分子的反应. 实验观测到Δ=1系列团簇(Y₂O₃)_NO^- (N=1~25)、(Y₂O₃)_NYO₂F^- (N=1~24)及Δ=4系列团簇(Y₂O₃)_NYO₄^- (N=1, 3~24)具有氢抽取反应活性, N≥2时其它Δ系列团簇(Δ=0, 2, 3, 5)在相同实验条件下没有表现出明显的反应性. 密度泛函理论研究Δ=1或4系列小尺寸团簇(Y₂O₃)_NY_xO_yF_0,1^- (N≤4;x=0, 1)的结构揭示O^-•自由基是氢抽取反应的活性位点, 结合实验可推测Δ=1或4系列纳米尺寸团簇(Y₂O₃)_NY_xO_yF_0,1^- (x=0, 1)结构中也含有O^-•自由基. 这些结果表明Δ=0系列惰性纳米尺寸团簇(Y₂O₃)_NYO₂^-可以通过吸附一个O₂分子发生电子转移生成O^-•自由基(O^2-+O₂→O^-•+O₂^-•), 也可以通过掺入F原子的方式生成O^-•自由基(O^2-+F^•→O^-•+F^-).     

Preparation, properties, and reactions of metal-containing heterocycles: Part CV. Synthesis and structure of polyoxadiphosphaplatinaferrocenophanes

A series of novel heterobimetallic crown ether-like polyoxadiphosphaplatinaferrocenophanes cis-[1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂PPh₂)₂]PtCl₂ (n=1–3) (4a–c) was synthesized in good yield by cyclization of the bis(phosphine) ligands 1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂PPh₂)₂ (n=1–3) (3a–c) and (PhCN)₂PtCl₂ under high dilution conditions in CH₂Cl₂. The bisphosphines 3a–c are obtained by reaction of the corresponding diols 1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂OH)₂ (n=1–3) (1a–c) with: (i) CH₃SO₂Cl in CH₂Cl₂ and (ii) LiPPh₂ in THF. Although the X-ray crystal structure of 4a shows that the cavity is large enough for the encapsulation of small metal cations, inclusion experiments of 4a–c with Group 1 cations, and Mg²⁺, or NH₄⁺ in solution applying NMR titration and cyclovoltammetric methods reveal no evidence for the formation of host–guest complexes for 4a,b. In the case of 4c only the addition of Na⁺ or K⁺ leads to an insignificant effect.     

The excess molar volumes of (an alkanol + a branched chain ether) at the temperature 298.15 K and the application of the ERAS model

The excess molar volumes V_m^E {x(CH₃OH or CH₃CH₂OH or CH₃(CH₂)₂OH or CH₃CH(OH)CH₃ + (1 - x){CH₃(CH₂)₂}₂O or CH₃C(CH₃)₂OCH₃ or CH₃CH₂C(CH₃)₂OCH₃} have been calculated from measured values of density over the whole composition range at the temperature 298.15 K in order to investigate OH … O specific interactions. The results are explained in terms of the strong self-association of the alkanols, the specific interaction between the alkanol, and the ether molecules and packing effects upon mixing. The experimental V_m^h results presented here, together with the previously reported data for the molar excess enthalpy H_m^E, has been used to test the Extended Real Associated Solution (ERAS) model.     

CH3CF2O2与HO2自由基反应机理的理论研究

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CH₃CF₂O₂与HO₂自由基反应机理. 结果表明, CH3CF₂O₂与HO₂自由基反应存在两条可行的通道. 通道CH3CF₂O₂＋HO₂→IM1→TS1→CH₃CF₂OOH＋O₂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O₂和CH₃CF₂OOH. 这与实验结果是一致的；而通道CH₃CF₂O₂＋HO₂→IM2→TS2→IM3→TS3→IM4＋IM5→IM4＋TS4→IM4＋OH＋O₂→TS5＋OH＋O₂→CH₃＋CF₂O＋OH＋O₂→CH₃OH＋CF₂O＋O₂的控制步骤活化能为93.42 kJ•mol^－1，其产物是CH₃OH、CF₂O和O₂. 结果表明这条通道也能发生，这与前人的实验结果一致.     

Highly stereoselective reduction of methyl ketone complexes of the chiral Lewis acid [(η-C5H5)Re(NO)(PPh3)] by K(s-C4H9)3BH; synthesis of optically active secondary alcohols and derivatives

Reaction of optically active ketone complexes (+)-(R)-[(η⁵-C₅H₅)Re(NO)-(PPh₃)(η¹-O=C(R)(CH₃)]⁺ BF₄⁻ (R = CH₂CH₃, CH(CH₃)₂m C(CH₃)₃, C₆H₅) with K(s-C₄H₉)₃BH gives alkoxide complexes (+)-(RS)-(η⁵-C₅H₅)Re(NO)(PPh₃)-(OCH(R)CH₃) (73–90%) in 80–98% de. The alkoxide ligand is then converted to Mosher esters (93–99%) of 79–98% de.     

Rate constants for the reaction of OH radicals with CH3CN, C2H5CN AND CH2=CH-CN in the temperature range 298–424 K

Rate constants for the reactions of OH with CH₃CN, CH₃CH₂CN and CH₂=CH-CN have been measured to be 5.86 × 10⁻¹³ exp(−1500 ± 250 cal mole⁻¹/RT), 2.69 × 10⁻¹³ exp(−1590 ± 350 cal mole⁻¹/RT and 4.04 × 10⁻¹² cm³ molecule⁻¹ s⁻¹, respectively in the temperature range 298–424 K. These results are discussed in terms of the atmospheric lifetimes of nitrfles.     

Vibrational spectra and density functional study of propylgermane

Raman and infrared spectra of propylgermane, CH₃CH₂CH₂GeH₃, and its Ge-deuterated analog, CH₃CH₂CH₂GeD₃, were investigated in their gaseous, liquid and solid states. The normal coordinate treatment was carried out by density functional theory (DFT) calculation, using B3LYP/6-31G^* and 6-311++G^** basis sets, and the corresponding fundamental vibrations were assigned. The trans (T) and gauche (G) forms around the central C–C bond coexisted in the gaseous and liquid states and only the T form existed in the solid state. From the temperature dependent measurements of the Raman spectra in the liquid state, the enthalpy difference was found to be ΔH(T−G)=−0.36±0.02 kcalmol⁻¹ with the T form being more stable. The energy differences between the isomers obtained by DFT calculations were ΔE(T−G)=−0.46 kcalmol⁻¹ and ΔE(T−G)=−0.87 kcalmol⁻¹ by the 6-31G^* basis set and 6-311++G^** basis set, respectively.     

Pyrolysis and film growth studies of phosphinoborane compounds

Chemical vapor deposition experiments were conducted using phosphinoborane compounds of the type [R₂BPR′₂]_n, where R = CH₂CH₃ (1) or CH₃ (2), R′= C(CH₃)₃, and R = CH₂CH₃ (3) or CH₃ (4), R′ = Si(CH₃)₃. Thin films were deposited on Si substrates at 300–850°C under vacuum using 1–3, while no film formed using 4. All films contained considerable carbon (C/B = 0.67–7) and were deficient in phosphorus (P/B = 0-0.5) according to Auger electron spectroscopy. For 3, silicon was incorporated in the films (Si/B = 0.9–2). The preferential loss of phosphorus was nearly complete at higher pyrolysis temperatures that favor formation of carbon-rich films. Volatile products of the decompositions were observed by in situ mass spectroscopy and by ¹H nuclear magnetic resonance analysis of the condensate in a liquid nitrogen cooled trap. The products indicate that β-hydrogen elimination of alkene from boron is a preferred reaction pathway, while concerted elimination reactions appear to be inefficient. Although these phosphinoborane compounds do not appear to be suitable precursors for pure boron phosphide, the B-P-C films obtained are chemically inert and may be of interest as protective coatings.     

A Fourier transform infrared study of the lamellar liquid crystalline phase of dimethyldodecyl amineoxide-water and dimethyldodecyl amineoxide-gramicidin-D-water systems

The overall conformational order of the alkyl tail of the lyotropic lamellar phase of the dimethyldodecyl amineoxide, (CH₃)₂ON⁺(CH₂)₁₁CH₃ (DDAO)---H₂O system (75.7 wt.%) has been studied by using Fourier transform infrared spectroscopy. The spectral region 1000–1400 cm⁻¹, covering the CH₂ wagging modes and the methyl umbrella modes of DDAO, has been recorded in the temperature interval 3–60°C and at different mole fractions of gramicidin-D with respect to DDAO (X_g = 0.03, 0.05 and 0.1) for both DDAO-H₂O and DDAO-D₂O systems. It has been shown that the DDAO amphiphile molecules of the lamellar phase reorganise in a phase-like transition near 25–30°C. The DDAO-water system does not show any significant bands corresponding to a double gauche conformation at 1355 cm⁻¹ nor to a gauche-transgauche (kinked) conformation at 1367 cm⁻¹. These bands are probably present but hidden in the broad low-frequency side of the CH₃ umbrella band at 1377 cm⁻¹. Upon incorporation of gramicidin into the lamellar phase both head group and acyl chain spectra of the lipid change in such a way as to indicate a decreased “ordering” of the molecules, as judged by comparison with spectra of the same molecule in a micellar environment, and with increased fluidity of the acyl chains.     

Studies on organolanthanide complexes : LXIII. Synthesis, spectroscopic and X-ray crystallographic characterization of new early organolanthanide, organoyttrium hydride and organoholmium hydroxide complexes

Organolanthanide chloride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-Cl)]₂ (Ln = La, Pr, Ho and Y) react with excess NaH in THF at 45°C to give the dimeric hydride complexes [(CH₃OCH₂CH₂C₅H₄)₂Ln(μ-H)]₂, which have been characterized by IR, ¹H NMR, MS and XPS spectroscopy, elemental analyses and X-ray crystallography. [(CH₃OCH₂CH₂C₅H₄)₂Y(μ-H)]₂ crystallizes from THF/n-hexane at −30°C, in the triclinic space group P1 with a = 8.795(2) Å, b = 11.040(1) Å, c = 16.602(2) Å, = 93.73(1)°, β = 91.82(1)°, γ = 94.21(1)°, D_c = 1.393 gcm⁻³ for Z = 2 dimers. However, crystals of [(CH₃OCH₂CH₂C₅H₄)₂Ho(μ-OH)]₂ were obtained by recrystallization of holmium hydride in THF/n-hexane at −30°C, in the orthorhombic space group Pbca with a = 11.217(2) Å, b = 15.865(7) Å, c = 17.608(4) Å, D_c = 1.816 gcm⁻³ for Z = 4 dimers. In the complexes of yttrium and holmium, each Ln atom of the dimers is coordinated by two substituted cyclopentadienyl ligands, one oxygen atom and two hydrogen atoms (for the Y atom) or two hydroxyl groups (for the Ho atom) to form a distorted trigonal bipyramid if the C(η⁵)-bonded cyclopentadienyl is regarded as occupying a single polyhedral vertex.