A Gaussian-2 ab initio study of [C2H5S] ions: III. H2 and CH4 eliminations from CH3CHSH and CH3SCH2

Gaussian-2 ab initio calculations were performed to examine the six modes of unimolecular dissociation of cis-CH₃CHSH⁺ (1⁺), trans-CH₃CHSH⁺ (2⁺), and CH₃SCH₂⁺ (3⁺): 1⁺→CH₃⁺+trans-HCSH (1); 1⁺→CH₃+trans-HCSH⁺ (2); 1⁺→CH₄+HCS⁺ (3); 1⁺→H₂+c-CH₂CHS⁺ (4); 2⁺→H₂+CH₃CS⁺ (5); and 3⁺→H₂+c-CH₂CHS⁺ (6). Reactions (1) and (2) have endothermicities of 584 and 496 kJ mol⁻¹, respectively. Loss of CH₄ from 1⁺ (reaction (3)) proceeds through proton transfer from the S atom to the methyl group, followed by cleavage of the C–C bond. The reaction pathway has an energy barrier of 292 kJ mol⁻¹ and a transition state with a wide spectrum of nonclassical structures. Reaction (4) has a critical energy of 296 kJ mol⁻¹ and it also proceeds through the same proton transfer step as reaction (3), followed by elimination of H_2. Formation of CH₃CS⁺ from 2⁺ (reaction (5)) by loss of H₂ proceeds through protonation of the methine (CH) group, followed by dissociation of the H₂ moiety. Its energy barrier is 276 kJ mol⁻¹. On both the MP2/6-31G* and QCISD/6-31G* potential-energy surfaces, the H₂ 1,1-elimination from 3⁺ (reaction (6)) proceeds via a nonclassical intermediate resembling c-CH₃SCH₂⁺ and has a critical energy of 269 kJ mol⁻¹.     

木质素二聚体模型化合物热解机理的量子化学研究

β-O-4连接是木质素主体结构单元之间的主要联结方式。采用密度泛函理论方法B3LYP,在6-31G (d, p)基组水平上,对β-O-4型木质素二聚体模型化合物(1-愈创木基-2-(2-甲氧基苯氧基)-1,3丙二醇)的热解反应机理进行了研究。提出了三种热解反应途径:C_β-O键均裂的后续反应、C_α-C_β键均裂的后续反应以及协同反应。对各种反应的反应物、产物、中间体和过渡态的结构进行了能量梯度全优化,计算了各热解反应途径的标准动力学参数。分析了各种主要热解产物的形成演化机理以及热解过程中温度对热解机理的影响。计算结果表明,C_β-O键的均裂反应和协同反应路径(1)和(3)是木质素二聚体热解过程中主要的反应路径,而C_α-C_β键的均裂反应和协同反应路径(2)和(5)是主要的竞争反应路径;热解的主要产物是酚类化合物如愈创木酚、1-愈创木基-3-羟基丙酮、3-愈创木基-3-羟基丙醛、愈创木基甲醛和乙烯等。在热解低温阶段协同反应是热解过程中的主要反应形式,而在高温阶段自由基均裂反应是热解过程的主要反应形式。     

A novel entry into a new class of spiroheterocyclic framework: regioselective synthesis of dispiro[oxindole-cyclohexanone]pyrrolidines and dispiro[oxindole-hexahydroindazole]pyrrolidines

2,6-Bis(arylmethylidene)cyclohexanones undergo a regioselective 1,3-dipolar cycloaddition reaction with the azomethine ylide derived from isatin and sarcosine by a decarboxylative route affording a series of 1-N-methyl-spiro[2.3¹]oxindole-spiro[3.2¹¹]6¹¹-arylmethylidenecyclohexanone-4-aryl-pyrrolidines which were further annulated to give a series of novel 1-N-methyl-spiro[2.3¹]oxindole-spiro[3.7¹¹](3¹¹-aryl)Δ^111,711a-hexahydro-2H-indazole-4-aryl-pyrrolidines. The structures of which were established by spectroscopic techniques as well as single crystal X-ray analysis.     

超声-气相联合扩散法快速合成ZIF-8用于硝基芳香化合物炸药的传感

三维微孔沸石咪唑基骨架(ZIF-8)纳米晶通过超声-气相联合扩散法快速合成.对该纳米晶进行荧光研究表明,纳米晶对硝基芳香化合物炸药具有良好的荧光淬灭能力.通过建立的Stern-Volmer方程,在1×10-4～8×10-4 mol/L范围内,每种炸药的浓度与纳米晶的荧光淬灭程度呈线性关系.对于2,4,6-三硝基苯酚(T...     

Ab initio study of the two competitive channels HO2 + H → H2 + O2 and HO2 + H → H2O + O

Saddle point geometries and barrier heights have been calculated for the H abstraction reaction HO₂(²A″)+H(²S) → H₂(¹Σ⁺_g)+O₂(³Σ⁻_g) and the concerted H approach-O removing reaction HO₂ (²A″)+H(²S) → H₂O(¹A₁)+O(³P) by using SDCI wavefunctions with a valence double-zeta plus polarization basis set. The saddle points are found to be of C_s symmetry and the barrier heights are respectively 5.3 and 19.8 kcal by including size consistent correction. Moreoever kinetic parameters have been evaluated within the framework of the TST theory. So activation energies and the rate constants are estimated to be respectively 2.3 kcal and 0.4×10⁹ ℓ mol⁻¹ s⁻¹ for the first reaction, 20.0 kcal and 5.4.10⁻⁵ ℓ mol⁻¹ s⁻¹ for the second. Comparison of these results with experimental determinations shows that hydrogen abstraction on HO₂ is an efficient mechanism for the formation of H₂ + O₂, while the concerted mechanism envisaged for the formation of H₂O + O is highly unlikely.     

Acetylation of dicarbonyl(η-cyclohexadiene)triphenyl- phosphineiron

Friedel-Crafts acetylation of dicarbonyl(η⁴-cyclohexadiene)triphenylphos-phineiron is accomplished in 96% yield under mild conditions to give dicarbonyl-(η⁴-5-endo-acetylcyclohexa-1,3-diene)triphenylphosphineiron. The structure of the product was established by direct comparison with the epimeric complex dicarbonyl(η⁴-5-exo-acetylcyclohexa-1,3-diene)triphenylphosphineiron produced by reaction of methyl magnesium iodide with dicarbonyl(η⁴-5-exo-cyanocyclohexa-1,3-diene)triphenylphosphineiron.     

γ-radiolysis and pulse radiolysis of aqueous 4-chloroanisole

Using pulse radiolysis and steady state γ-radiolysis in combination with product analysis by HPLC the radiolytic degradation mechanism of 4-chloroanisole (4-ClAn) has been elucidated. Pulse radiolysis experiments show that OH radicals react in neutral aqueous N₂O saturated solutions with 4-ClAn by addition to all aromatic ring positions to yield hydroxycyclohexadienyl radicals (OH-adducts), k(OH + 4-ClAn) = 6.5 × 10⁹dm³mol⁻¹s⁻¹. Those OH-adducts formed on ipso positions of the molecule subsequently undergo HCl or CH₃OH elimination forming methoxyphenoxyl- and chlorophenoxyl radicals. Their yield corresponds to 20% of the OH-radicals, whereby the distribution is roughly 3:1 in favor of the methoxyphenoxyl radicals, which reflects the stronger ortho-, para-directing activity of the methoxy group. The OH-adducts decay second order, 2k = 1 × 10⁹dm³mol⁻¹s⁻¹. The presence of oxygen leads to its addition on the hydroxycyclohexadienyl radicals, k(OH-adduct + O₂) = 3.2 × 10⁸dm³mol⁻¹s⁻¹. In airfree solution the reaction of H-atom with the substrate, k(H + 4-ClAn) = 1.2 × 10⁹dm³mol⁻¹s⁻¹, results in H-adducts which decay in bimolecular reactions, 2k = 8.2 × 10⁸dm³mol⁻¹s⁻¹. The rate constant for the reaction of the solvated electrons has been determined to k(e_aq⁻ + 4-ClAn) = 2 × 10⁹dm³mol⁻¹s⁻¹. The absorption spectra of H- and OH-adducts were measured in the range of 280–450 nm. The products analysed by HPLC after γ-radiolysis in dependence of dose (100–600 Gy) are given for N₂O-, air-, oxygen- and argon saturated neutral aqueous solutions. In conditions favoring the OH radical oxidation 4-chlorophenol, 4-methoxyphenol, 5-chloro-2-methoxyphenol and 2-chloro-5-methoxyphenol were determined as final products. In the presence of Ar, where about equal amounts of OH and e_aq⁻ are present, additionally anisole could be detected. Under both reaction conditions the amount of identified products is about 20% of decomposed 4-ClAn. The reaction of e_aq⁻ leads to reductive dechlorination which corresponds quantitatively to the degradation of the substrate. In the presence of air or solutions saturated with pure oxygen predominantly hydroquinone, 4-chlorophenol and muconic acids are formed and the material balance is 50%. The efficient dechlorination (60% of the decomposed 4-ClAn) as well as ring fragmentation products as intermediates en route to complete mineralization in oxygenated solution indicate that high energy radiation is a promising method for degradation of halogenated aromatic compounds in water. Variation of dose rates from 79 Gy min⁻¹ to 266 Gy min⁻¹ did not show any influence on the product distribution.     

Cu ion core conservation from reactant to product in the Cu+F2 chemiluminescent reaction

Electronic chemiluminescence from the reaction of selected ground state (²S_1/2) or metastable (²D_5/2, ²D_3/2) copper atoms with fluorine has been studied using a hollow cathode-flowing afterglow reactor. The observed signal related to the Cu(²S) and Cu*(²D) atom densities, indicate that the chemiluminescence cross-section for Cu*(²D) atoms is about 10⁴ times larger than for Cu(²S) atoms. This strong propensity is explained in terms of a direct reaction, initiated by a harpooning process, during which the Cu⁺ ion core of the reactant (3d¹⁰ for Cu(²S) and 3d⁹4s for Cu*(²D)) is conserved in the products (ionic structure Cu⁺(3d¹⁰)F⁻ for the CuF ground state and Cu⁺(3d⁹4s)F⁻ for the CuF*(a, A, B, C, D) chemiluminescent states).     

1,3,2-Diazastanna-[3]ferrocenophanes bearing alkyn-1-yl groups at tin and their 1,1-organoboration with triethylborane—molecular structure of a novel spirotin compound

2,2-Dichloro-1,3-bis(trimethylsilyl)-1,3,2-diazastanna-[3]ferrocenophane (3) reacts with lithium alkynides LiCCR¹ to give the corresponding di(alkyn-1-yl)tin derivatives 4a (R¹=^tBu) and 4b (R¹=SiMe₃). 1,1-Organoboration of 4 with triethylborane affords the spirotin compounds 5 which contain both a ferrocenophane and a stannacyclopentadiene ring. The crystal structure of 5b was determined by X-ray analysis. The compounds 4 and 5 were characterised in solution by multinuclear magnetic resonance (¹H-, ¹¹B-, ¹³C-, ¹⁵N-, ²⁹Si-, ¹¹⁹Sn-NMR), using pulsed field gradients in HMBC experiments for the ¹H detected ¹⁵N- and ¹¹⁹Sn-NMR signals. The compound 5b was also studied by solid-state ¹³C, ²⁹Si and ¹¹⁹Sn MAS NMR in order to correlate liquid and solid-state NMR data with the structural evidence.     

1,3-丙二胺邻苯二酚钼钨手性八面体配合物的仿生合成、晶体结构以及与ATP作用的液相NMR研究

合成了1,3-丙二胺邻苯二酚钼钨手性八面体配合物(NH₃CH₂CH₂CH₂NH₂)₂[Mo_0.4W_0.6O₂(C₆H₄O₂)₂],并对其进行了单晶结构解析,研究了其与ATP作用的液相NMR谱.该晶体属正交晶系,空间群为Pcan.晶胞参数a=0.7501(2)nm,b=2.3994(7)nm,c=1.2178(4)nm,Z=4.[Mo_0.4W_0.6O₂(C₆H₄O₂)₂]^2-的配位几何构型为手性八面体,晶体为外消旋体.配位阴离子中MoW中心金属离子除了与两个端基O配位形成cis-MO键外,同时还分别与两个邻苯二酚配位基团的的氧原子配位,形成4个M-Ob(M=Mo,W)键,构成两个五元环.利用¹HNMR,¹³CNMR,³¹PNMR以及¹H-¹⁵NHMBC对标题配合物及其与ATP在D₂O溶剂中的作用进行了研究,发现标题配合物的MoW中心金属离子在纯D₂O溶剂中被还原成+5价,但与ATP混合后转化为+6价,且与原配位基邻苯二酚发生解离.解离后的[MO₂]²⁺最大可能与腺嘌呤上的氨基N原子配位,而此配位可能是其抗癌抗肿瘤活性的主要作用机理之一.     

An ab initio and DFT study on the hydrolysis of carbonyl dichloride

Hydrolysis of carbonyl dichloride or phosgene (Cl₂CO) in gas phase has been investigated at Hartree–Fock, density functional and ab initio levels of theory. The effects of basis sets on the energetics of the reaction have also been explored. Calculations reveal that initially carbonyl dichloride and water form a weak complex and this complex can react further in two ways. In Path 1, water adds on to carbonyl dichloride across carbonyl bond in a concerted fashion to give dichloromethane diol, and this diol decomposes to form chloro formic acid by syn-1,2-elimination of HCl and forms CO₂ and HCl as final products. Path 2 is the concerted addition of water across carbon chlorine bond and elimination of HCl in a single step leading to the formation of chloro formic acid directly. This second path that skips the formation of dichloromethane diol is observed to be very low lying and hence is kinetically favored. Addition of second water molecule to the reacting system is found to catalyze the reaction by stabilizing the complex, intermediate and transition states and reduces the activation energy to 24.6 kcal mol⁻¹ compared to 29.9 kcal mol⁻¹ for a single water molecule.     

纤维素热解形成左旋葡聚糖机理的理论研究

采用密度泛函理论UB3LYP/6-31G(d)方法,对模型化合物纤维二糖热解反应机理进行了量子化学理论计算研究。设计了三种可能的热解反应途径,对各种反应的反应物、产物、中间体和过渡态的结构进行了能量梯度全优化,计算了不同温度下热解反应的标准热力学和动力学参数。计算结果表明,糖苷键均裂而形成两个自由基中间体IM₁a和IM₁b,吸收热量为321.26kJ/mol,中间体IM₁a经过渡态TS₁a进一步形成左旋葡聚糖P₁,反应势垒为202.72kJ/mol;与分步反应相比,纤维二糖经过渡态TS₂协同反应直接形成左旋葡聚糖P₁和吡喃葡萄糖P₂的反应势垒低于分步反应的总势垒,其反应势垒为377.54kJ/mol;H⁺的加入有利于糖苷键的断裂,断裂形成的中间体IM₃很难进一步反应形成左旋葡聚糖。     

A study of the gas-phase reaction between protonated acetaldehyde and methanol

Protonated acetaldehyde is methylated on the oxygen during interaction with methanol in the gas phase. The ionic product of the ion/molecule reaction between methanol and protonated acetaldehyde is identical with C-protonated methylvinyl ether (high-pressure ionization), and with the (M − C₂H₅)⁺ fragment ion of sec-butyl methyl ether (following electron ionization), and also with the (M − OCH₃)⁺ fragment ion of acetaldehyde dimethylacetal (following electron ionization). The structures of these ions and the mechanism of their formation were established by isotope-labeling experiments and collision-induced dissociation mass spectra of model compounds obtained with three different types of tandem mass spectrometers (BEQQ, triple-quadrupole, and a penta-quadrupole instrument). Gas phase synthesis of the product ion from [²H₃]-methanol or [²H₄]-acetaldehyde provided insight into its mode of formation and collision-induced dissociation.     

脉冲辐解研究喹啉和异喹啉与瞬态粒子的反应

通过合理控制反应条件, 使体系在电子束脉冲作用后只剩下所需要的一种瞬态粒子, 用脉冲辐解研究了喹啉、异喹啉分别与水合电子、羟基自由基、氢自由基等几种典型的氧化还原瞬态粒子的反应过程, 研究了各种瞬态产物的吸收光谱及其变化规律, 测定了相关反应的速率常数. 喹啉、异喹啉与水合电子的反应速率常数分别为7.1×10⁹和3.4×10⁹ mol^-1·L·s^-1, 与羟基自由基的反应速率常数分别为7.2×10⁹和3.4×10⁹ mol^-1·L·s^-1, 与氢自由基的反应速率常数分别为5.7×10⁹和3.6×10⁹ mol^-1·L·s^-1. 这一结果表明, 喹啉、异喹啉均能够非常迅速地与水合电子、羟基自由基、氢自由基发生反应, 喹啉比异喹啉的反应速率更快. 运用电子理论分析了瞬态反应产物结构的稳定性差异, 结果表明, 喹啉的反应产物比异喹啉的稳定, 从而揭示了喹啉比异喹啉反应速率快的原因.     

Properties of phenoxyl radical of dehydrozingerone, a probable antioxidant

Free radical reactions of dehydrozingerone (DZ), a methoxy phenol, were studied at dfferent pHs with a variety of oxidants using nanosecond pulse radiolysis technique. Hydroxyl radical (OH) reaction with the phenolic form at pH 6 led mainly to the formation of an OH-adduct absorbing at 460 nm in addition to a minor oxidation product. On the other hand, at pH 10 with the deprotonated phenoxide ion, the only reaction observable was oxidation generating a phenoxyl radical absorbing at 360 nm. HPLC analysis indicated formation of two different products at pH 6 from addition and oxidation reactions, whereas at pH 10, only the oxidation product was detectable. Reactions of more specific secondary oxidizing radicals, N3√, Br√, Br⁻₂√ and Tl(II) with DZ gave rise to the phenoxyl radical over the entire pH range. DZ in the phenoxide ion form reacted with nitrogen dioxide and trichloromethyl peroxyl radicals with rate constants 6×10⁸ and 8.8×10⁸ dm³ mol⁻¹ s⁻¹ respectively leading to the phenoxyl radicals. The DZ phenoxyl radical reacted with trolox C (an analogue of -tocopherol) with a rate constant of 8.3×10⁷ dm³ mol⁻¹ s⁻¹. One electron reduction potential of the DZ phenoxyl radical at pH 6 was determined to be +1.1 V vs NHE using N3√/N⁻₃ as the standard couple.     

Preparation of palladium complexes of 1,3-di(2-pyridyl)propane derivatives and their use in norbornene polymerization

A variety of neutral palladium(II) complexes [Pd(L–L)Cl₂] containing 1,3-di(2-pyridyl)propane (1), 1,3-bis(2-pyridyl)-2-pentylpropane (2), 1,3-bis(2-pyridyl)-2-phenylpropane (3a), 1,3-bis(2-pyridyl)-2-tolylpropane (4), and 1,3-bis(2-pyridyl)-2-ferrocenylpropane (5) as chelate ligands (L–L) have been synthesized. The crystal structures of 1,3-diphenyl-2,4-di-pyridin-2-yl-butan-1-ol (3b), 5, [(2)PdCl₂], [(4)PdCl₂], and [(5)PdCl₂] have been determined and show a square planar geometry at palladium(II). The neutral complexes were tested in the polymerization of norbornene and copolymerization of norbornene with norbornene derivatives. The complex bearing the pentyl group exhibited high reactivity to give up to 5.9×10⁵ in molecular weight for the homopolymerization. When [(4)PdCl₂] or [(5)PdCl₂] was used as a catalyst, homopolymers insoluble at 150 °C in trichlorobenzene were obtained. However, copolymerization of norbornene with norbornene derivatives 8a–d catalyzed by [(4)PdCl₂] gave soluble copolymers with molecular weights up to 5.1×10⁵.     

New cycloaddition reactions of 1-phenyl-4-vinylpyrazole

1-Phenyl-4-vinylpyrazole reacts with methyl propiolate and N-phenylmaleimide giving via the Diels-Alder 1:1 adducts, products (4) and (8), and also the 1:2 adducts (5), (6) and (9) resulting from an “ene” reaction of the initially forced cycloadducts. The obtention of the adducts (5) and (6) in equimolecular amounts is a good example of the non-regioselective character of the “ene” reaction. The reaction with tetracyanoethylene takes place through the olefinic substituent giving the π² + π² adduct (10).     

Reactions of Cp Ru(η-C6H5CHO) OSO2CF3 (Cp = C5Me5) with substituted anilines forming ruthenium Schiff base complexes

Cp^* Ru(η⁶-C₆H₅CHO)⁺OSO₂CF₃⁻ (1) (Cp^* = C₅Me₅) reacts with substituted anilines forming ruthenium Schiff base complexes containing an η⁶-coordinated Cp^* Ru⁺ group. The 2:1 reaction of 1 with 1,4-phenylenediamine yielded only the monocondensation product, whereas the 2:1 reaction of 1 with 1,4-xylylenediamine yielded the dicondensation product.     

Photosensitization study of cage-like metal complexes with hexadentate ligands, tptn and tpen. Part 2. Electron transfer photosensitization via ion pairs: cobalt(III)(tptn)—iodide ion and cobalt(III)(tpen)—iodide ion systems

Co(tptn)³⁺ and Co(tpen)³⁺ (where tptnN,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-propanediamine and tpen N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine) are demonstrated to have a similar photosensitization capacity to other caged Co(III) complexes such as Co(sepulchrate)³⁺. In oxygen-saturated aqueous solutions at pH 4.0, a photoassisted oxidation of I⁻ to I₃⁻ by O₂ is obtained with a turnover number of greater than 12 for both Co(tptn)³⁺ and Co(tpen)³⁺. Quantum yields for the formation of I₃⁻ are 8.7x 10⁻⁴ and 1.6x 10⁻² respectively at pH 4.0 in solution with a constant supply of air.     

可见光敏引发聚合甲基丙烯酸甲酯的动力学研究

本论文用膨胀计法进行了甲基丙烯酸甲酯在氯仿溶液中可见光光敏引发聚合动力学的研究。此光敏引发体系由光敏剂1,3,3-三甲基-2-[5-(1,3,3-三甲基-2-吲哚叉)-1,3-戊二烯]吲哚碘盐(简称NK-529),引发剂邻氯代六芳基双咪唑(简称o-Cl-HABI),氢给体3-巯基-4-甲基-4氢-1,2,4-三氮唑(简称MTA)组成。研究结果表明,此光敏聚合体系的光聚合速率与各组分的动力学方程如下:R_p=K(NK-529)^0.51(HABI)^0.41(MTA)^0.36(MMA)^1.0.