甲硅硫醛(H2SiS)脱氢反应的反应路径解析

本文用内禀反应坐标(IRC)方法讨论了甲硅硫醛分子的脱氢反应机理. 在RHF/4-31G基组上对此反应做了量子化学从头计算和反应路径解析, 得到H_2SiS的平衡几何、过渡态结构、反应势能曲线、活化能, 反应热以及沿反应坐标一些物理量的变化, 并对平衡几何和过渡态做了振动分析. 同时, 计算了反应的频率因子A和在500 K时的活化熵△S≠。     

CH自由基和NO~2反应研究: II.反应的动力学计算

采用MP2(FULL)/6-31G(d)方法从动力学计算上探讨了CH自由基与NO~2反应的可能途径,找到了反应物,中间体及产物之间的能量通道和过渡态,报道了它们的构型、电子态及能量。并通过频率分析和IRC方法对所有的过渡态进行了验证。在此基础上求出了各步反应的活化能。在以前热力学研究的基础上,对于可能的反应通道进一步作了动力学分析,找到了反应主产物通道的分支比,与实验得到的分支比基本吻合。     

CH自由基和NO~2反应研究: II.反应的动力学计算

采用MP2(FULL)/6-31G(d)方法从动力学计算上探讨了CH自由基与NO~2反应的可能途径,找到了反应物,中间体及产物之间的能量通道和过渡态,报道了它们的构型、电子态及能量。并通过频率分析和IRC方法对所有的过渡态进行了验证。在此基础上求出了各步反应的活化能。在以前热力学研究的基础上,对于可能的反应通道进一步作了动力学分析,找到了反应主产物通道的分支比,与实验得到的分支比基本吻合。     

CH自由基和NO2反应研究Ⅱ.反应的动力学计算

采用MP2(FULL)/6-31G(d)方法从动力学计算上探讨了CH自由基与NO2反应的可能途径,找到了反应物,中间体及产物之间的能量通道和过渡态,报道了它们的构型、电子态及能量.并通过频率分析和IRC方法对所有的过渡态进行了验证.在此基础上求出了各步反应的活化能.在以前热力学研究的基础上,对于可能的反应通道进一步作了动力学分析,找到了反应主产物通道的分支比,与实验得到的分支比基本吻合.     

H2 + CN(n=0,1)→H + HCN振动选态反应

用从头算方法获得了Ｈ２＋ＣＮ反应的内禀反应坐标（ＩＲＣ），沿着ＩＲＣ，计算了各垂直于ＩＲＣ的简正模所对应的频率（Ｗ）以及沿ＩＲＣ运动与垂直ＩＲＣ运动的简正模之间的耦合常数（ＢＫＦ），根据传统过渡态，变分过渡态理论和选态公式，计算了ｎＣＮ＝０及ｎＣＮ＝１时反应的速率常数，并得到了实验相一致的结果，还计算了ｎＣＨ＝１及ｎＣＮ＝１的Ｈ＋ＨＣＮ→Ｈ２＋ＣＮ反应速率常数，可供实验工作者参考。     

HCN和氯反应动态学及产物振动态分布的计算

采用自洽场分子轨道UHF／6－311G**从头计算法,获得了HCN＋Cl→HCl＋CN反应的内禀反应坐标（IRC）。沿着IRC,计算了反应的动态学性质,根据传统过渡态、变分过渡态理论,得到了反应的理论速率常数,可供实验工作者参考,利用SCP－IOS近似下的产物振动跃迁几率公式,自编程序计算了HCN（004,302）＋Cl→HCl＋CN反应中产物CN的振动态分布,获得了和实验相一致的结果。     

四嗪与一些环烯烃反应机理的理论研究

采用多种密度泛函方法并辅以极化连续介质模型研究了四嗪与一些环烯烃发生[4+2]环加成反应的反应机理,得出反应过程按协同机理进行,即反应过程中只有一个过渡态. 主要使用的方法有：CAM-B3LYP,B3LYP,X3LYP,BMK,LC-wPBE,wB97x,wB97xd,M062x和M11. 这种过渡态的稳定性与前线分子轨道的相互作用有关,从过渡态电荷迁移的方向来看,环烯烃作为电子给体,而四嗪作为电子受体. 反应的难易取决于环烯烃的环的大小,环越大反应越难,这与环在形成过渡态时的变形能有关. 通过气相平动熵和溶液平动熵计算得到的活化自由能的数据,比较发现气相平动能得出的活化自由能离实验估计值相差很远. 而对于溶液中活化自由能垒数据对于大多数计算方法所得的结果比较接近,其中BMK,CAM-B3LYP和X3LYP的结果更合理一些. 同时也发现M062x和M11方法计算的反应速度常数与实验值差别较大,说明这些方法不太适合用来研究此类反应;而考虑色散作用的wB97xd也过高估计过渡态时分子之间的作用能,导致低自由能垒,具体产生的原因在文中进行了详细的讨论.     

单分子分解成两个自由基反应的半经典统计方法I. 关于CH4分解成CH3.和H.自由基的研究

本文计算了温度范围在300-1500K, CH4→CH3.+H.的分角反应中, 过渡态CH3...H的平均键长、频率因子、活化能及反应速率常数, 计算结果和实验结果符合得很好。     

次甲基硅SiH与HF反应的热力学及动力学性质研究

在量子化学对SiH与HF反应计算的基础上,运用统计热力学和Wigner校正的Eyring过渡态理论计算了该反应在200～2000K温度范围内的热力学函数、平衡常数、频率因子A和速率常数随温度的变化。计算结果表明该反应在低温下具有热力学优势,而在高温下具有动力学优势。该反应在研究的温度范围内是一放热、熵减少的反应,反应的速率常数随温度的升高而增大,且服从Arrhenius定律。     

单分子分解成两个自由基反应的半经典统计方法I. 关于CH4分解成CH3.和H.自由基的研究

本文计算了温度范围在300-1500K, CH4→CH3.+H.的分角反应中, 过渡态CH3...H的平均键长、频率因子、活化能及反应速率常数, 计算结果和实验结果符合得很好。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.