The host-guest interactions between cyclopentanocucurbit-[6]uril(CyP_(6)Q[6])as host and six alkyl imidazolium hydrochloride as guests(g1,g2,g3,g4,g5,and g6)have been studied by various techniques,such as^(1)H NMR spe...The host-guest interactions between cyclopentanocucurbit-[6]uril(CyP_(6)Q[6])as host and six alkyl imidazolium hydrochloride as guests(g1,g2,g3,g4,g5,and g6)have been studied by various techniques,such as^(1)H NMR spectroscopy,isothermal titration calorimetry,mass spectrometry,and single-crystal X-ray diffraction analysis.The experimental results showed that CyP6Q[6]formed 1:1 inclusion complexes with each of guests g1-g6.The part of the guest entered the cavity of CyP_(6)Q[6]changes as the alkyl chain increases in length.It can be seen that the length of the alkyl chain plays a key role in determining the mode of host-guest interactions.展开更多
自由基与分子反应是一类具有负活化能的非基元反应,通常认为是通过反应复合物的两步过程,在大气化学和碳氢燃料燃烧机理中广泛存在,且在理论计算和实验上广泛研究.以碳氢燃料燃烧机理中重要反应类羟基自由基提取烷基过氧化氢α位氢的反...自由基与分子反应是一类具有负活化能的非基元反应,通常认为是通过反应复合物的两步过程,在大气化学和碳氢燃料燃烧机理中广泛存在,且在理论计算和实验上广泛研究.以碳氢燃料燃烧机理中重要反应类羟基自由基提取烷基过氧化氢α位氢的反应为研究对象,通过量化计算揭示其反应规律,计算得到其精确动力学参数.在所研究反应类中,定义第一步反应复合物的生成反应的标准摩尔吉布斯自由能变化等于零时所对应的温度为其转折温度Tc,并表明了当T>>Tc时可采用稳态近似法处理该类反应体系,得到总包反应速率常数.所有反应涉及的物种几何结构优化和频率分析均在BHand HLYP/6-311G(d,p)水平下得到,并在所研究反应类中选取了5个代表反应,通过CCSD(T)/CBS单点能计算,得到其最高转折温度为195.17 K,远远低于碳氢燃料燃烧模拟通常关注温度范围的最低温度650 K,表明用稳态近似法处理该类负活化能反应体系是合理的.计算还表明,该类反应的过渡态反应中心几何结构守恒,因此可将等键反应方法引入类反应,通过对低水平从头算得到的反应能垒进行校正,以得到高精度的结果.为了验证等键反应方法的可靠性,选取5个反应作为研究对象,将低水平BHand HLYP/6-311G(d,p)的校正结果和高水平CCSD(T)/CBS直接计算的结果进行比较,反应能垒最大绝对偏差由校正前的19.99 k J·mol-1降到校正后的1.47 k J·mol-1,表明用等键反应方法,只需在低水平从头算水平下就可以得到高水平的计算结果,从而可解决大分子体系精确动力学参数缺乏的问题.利用等键反应方法计算了20个反应的反应能垒,并结合过渡态理论计算得到了总包反应的速率常数,并揭示了该类反应只在低温段呈现负活化能关系.展开更多
The polymerization of alkyl isocyanates catalyzed by rare earth chloride salen complexes/triisobutyl aluminum (Ln(H<sub>2</sub>salen)<sub>2</sub>Cl<sub>3</sub>·2C<sub>2&l...The polymerization of alkyl isocyanates catalyzed by rare earth chloride salen complexes/triisobutyl aluminum (Ln(H<sub>2</sub>salen)<sub>2</sub>Cl<sub>3</sub>·2C<sub>2</sub>H<sub>7</sub>OH/Al(i-Bu)<sub>3</sub>) at room temperature was investigated. The influences of ligand structure, catalyst composition, polymerization temperature, polymerization time, the concentration of catalyst and monomer, and the polymerization solvent on the polymerization of isocyanates were studied. It was found that under the polymerization conditions, examined La(H<sub>2</sub>salen<sub>A</sub>)<sub>2</sub>Cl<sub>3</sub>·2C<sub>2</sub>-H<sub>7</sub>OH/Al(i-Bu)<sub>3</sub> (H<sub>2</sub>salen<sub>A</sub>= N,N′-disalicylideneethylene diamine) is a fairly high efficient catalyst for the polymerization of n-hexyl isocyanate (n-HexNCO) to prepare high molecular weight poly(n-hexyl isocyanate) (PHNCO) with narrower molecular weight distribution at room temperature. PHNCO could be prepared with yield of 74.0%, number-average molecular weight (M <sub>n</sub>) of 40.20×10<sup>4</sup> and MWD of 1.79 under the following optimum conditions: [Al]/[La] = 30 (molar ratio), [n-HexNCO]/[La] = 100 (molar ratio), [n-HexNCO] = 3.43 mol/L polymerization at 20°C for 12 h in toluene. In the same polymerization conditions, poly (n-octyl isocyanate) (PONCO) with yield of 67.3%, and poly(n-butyl isocyanate) (PBNCO) with yield of 45.5%, could be prepared respectively. The kinetics of the polymerization of n-HexNCO was also investigated and found to be first-order with respect to both monomer and catalyst concentrations.展开更多
A silica gel supported cobalt（lI） Schiff base complex was synthesized and used for the oxidation of alkyl aromatics using molecular oxygen as an oxidant under atmosphere pressure. The catalyst shows a high conversio...A silica gel supported cobalt（lI） Schiff base complex was synthesized and used for the oxidation of alkyl aromatics using molecular oxygen as an oxidant under atmosphere pressure. The catalyst shows a high conversion of alkyl aromatics and selectivity to benzylic ketones, and could be reused at least 5 times without significant loss of catalytic activity.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.21762011)the Guizhou Science and Technology Planning Project,China(Guizhou Science and Technology Cooperation Platform Talent)(No.20175788)the Guizhou Province Graduate Education Innovation Project,China[No.YJSCXJH(2020)188].
文摘The host-guest interactions between cyclopentanocucurbit-[6]uril(CyP_(6)Q[6])as host and six alkyl imidazolium hydrochloride as guests(g1,g2,g3,g4,g5,and g6)have been studied by various techniques,such as^(1)H NMR spectroscopy,isothermal titration calorimetry,mass spectrometry,and single-crystal X-ray diffraction analysis.The experimental results showed that CyP6Q[6]formed 1:1 inclusion complexes with each of guests g1-g6.The part of the guest entered the cavity of CyP_(6)Q[6]changes as the alkyl chain increases in length.It can be seen that the length of the alkyl chain plays a key role in determining the mode of host-guest interactions.
文摘自由基与分子反应是一类具有负活化能的非基元反应,通常认为是通过反应复合物的两步过程,在大气化学和碳氢燃料燃烧机理中广泛存在,且在理论计算和实验上广泛研究.以碳氢燃料燃烧机理中重要反应类羟基自由基提取烷基过氧化氢α位氢的反应为研究对象,通过量化计算揭示其反应规律,计算得到其精确动力学参数.在所研究反应类中,定义第一步反应复合物的生成反应的标准摩尔吉布斯自由能变化等于零时所对应的温度为其转折温度Tc,并表明了当T>>Tc时可采用稳态近似法处理该类反应体系,得到总包反应速率常数.所有反应涉及的物种几何结构优化和频率分析均在BHand HLYP/6-311G(d,p)水平下得到,并在所研究反应类中选取了5个代表反应,通过CCSD(T)/CBS单点能计算,得到其最高转折温度为195.17 K,远远低于碳氢燃料燃烧模拟通常关注温度范围的最低温度650 K,表明用稳态近似法处理该类负活化能反应体系是合理的.计算还表明,该类反应的过渡态反应中心几何结构守恒,因此可将等键反应方法引入类反应,通过对低水平从头算得到的反应能垒进行校正,以得到高精度的结果.为了验证等键反应方法的可靠性,选取5个反应作为研究对象,将低水平BHand HLYP/6-311G(d,p)的校正结果和高水平CCSD(T)/CBS直接计算的结果进行比较,反应能垒最大绝对偏差由校正前的19.99 k J·mol-1降到校正后的1.47 k J·mol-1,表明用等键反应方法,只需在低水平从头算水平下就可以得到高水平的计算结果,从而可解决大分子体系精确动力学参数缺乏的问题.利用等键反应方法计算了20个反应的反应能垒,并结合过渡态理论计算得到了总包反应的速率常数,并揭示了该类反应只在低温段呈现负活化能关系.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20304011, 20774078 & 20434020)the Special Funds for Major Basic Research Projects (Grant No. 2005CB623802)
文摘The polymerization of alkyl isocyanates catalyzed by rare earth chloride salen complexes/triisobutyl aluminum (Ln(H<sub>2</sub>salen)<sub>2</sub>Cl<sub>3</sub>·2C<sub>2</sub>H<sub>7</sub>OH/Al(i-Bu)<sub>3</sub>) at room temperature was investigated. The influences of ligand structure, catalyst composition, polymerization temperature, polymerization time, the concentration of catalyst and monomer, and the polymerization solvent on the polymerization of isocyanates were studied. It was found that under the polymerization conditions, examined La(H<sub>2</sub>salen<sub>A</sub>)<sub>2</sub>Cl<sub>3</sub>·2C<sub>2</sub>-H<sub>7</sub>OH/Al(i-Bu)<sub>3</sub> (H<sub>2</sub>salen<sub>A</sub>= N,N′-disalicylideneethylene diamine) is a fairly high efficient catalyst for the polymerization of n-hexyl isocyanate (n-HexNCO) to prepare high molecular weight poly(n-hexyl isocyanate) (PHNCO) with narrower molecular weight distribution at room temperature. PHNCO could be prepared with yield of 74.0%, number-average molecular weight (M <sub>n</sub>) of 40.20×10<sup>4</sup> and MWD of 1.79 under the following optimum conditions: [Al]/[La] = 30 (molar ratio), [n-HexNCO]/[La] = 100 (molar ratio), [n-HexNCO] = 3.43 mol/L polymerization at 20°C for 12 h in toluene. In the same polymerization conditions, poly (n-octyl isocyanate) (PONCO) with yield of 67.3%, and poly(n-butyl isocyanate) (PBNCO) with yield of 45.5%, could be prepared respectively. The kinetics of the polymerization of n-HexNCO was also investigated and found to be first-order with respect to both monomer and catalyst concentrations.
基金the financial support from the National Natural Science Foundation of China–Academy of Engineering Physics(No.10976014)Natural Science Foundation of Jiangsu Province(No.BK2011697)
文摘A silica gel supported cobalt（lI） Schiff base complex was synthesized and used for the oxidation of alkyl aromatics using molecular oxygen as an oxidant under atmosphere pressure. The catalyst shows a high conversion of alkyl aromatics and selectivity to benzylic ketones, and could be reused at least 5 times without significant loss of catalytic activity.
