金刚石(111)氢化表面脱氢势垒的量子化学研究

采用MNDO(UHF)方法,计算金刚石(111)面的脱氢势垒。在与气相有机分子脱氢活化能实验值系统比较的基础上,在一组尺度不同的金刚石表面团簇模型上进行了计算,结果收敛于42±4kJ/mol.并与MNDO(RHF)和AM1(UHF、RHF)方法给出的相应结果进行了比较。     

氯化聚乙烯对甲基丙烯酸甲酯／苯乙烯共聚动力学的影响

将甲基丙烯酸甲酯（ＭＭＡ）／苯乙烯（Ｓ）在氯化聚乙烯（ＣＰＥ）存在下进行悬浮溶胀接枝共聚，考察了ＣＰＥ对ＭＭＡ／Ｓ共聚动力学行为的影响．ＣＰＥ提高了聚合体系的粘度，使自动加速提前，扩散因素增加，对共聚有阻滞作用．ＣＰＥ是链转移剂，使ＭＭＡ／Ｓ共聚物分子量降低．ＣＰＥ对ＭＭＡ的吸附渗透优于对Ｓ的吸附，造成接技部分与非接技部分组成的差异．ＣＰＥ含量、溶胀时间、转化率、硫酸用量对共聚组成均有影响。     

引发甲基丙烯酸甲酯聚合的聚丙烯酰胺－氯化铜配合物膜催化剂表征

考察甲基丙烯酸甲酯在室温Ｎａ２ＳＯ３水溶液的聚合能力，发现在该溶液添加聚丙烯酰胺（ＰＡＡｍ）－氯化铜（ＣｕＣｌ２）配合物膜以组成ＰＡＡｍ－ＣｕＣｌ２膜／Ｎａ２ＳＯ３催化引发体系是必不可少的．采用ＥＳＲ、ＩＲ、ＸＰＳ和电导率等手段研究该体系催化剂的表面结构．结果表明，膜的单位面积平均含铜量在一定范围内和配位体种类等对催化活性有显著影响，即催化性能与催化剂的表面结构紧密相关．     

合成方法对MCM-22分子筛的结构、性质及催化性能的影响

在水热条件下分别以动态法和静态法合成了高纯度和高结晶度的MCM-22分子筛.采用N2吸附、XRD、TEM和FTIR等方法研究了制备方法对分子筛的结构及性质的影响.结果表明,动态法合成的MCM-22比静态法合成的分子筛的晶粒小,酸量低.在丙酮一步法合成甲基异丁基酮反应中,静态条件下合成的MCM-22为载体的催化剂的丙酮转化率较高,这是由于该分子筛的酸量较高所致.而MIBK的选择性则呈相反趋势,这可能与动态条件下合成的分子筛粒径小、孔道短有关.     

庚酸甲酯高温燃烧化学动力学机理的系统简化和分析

采用详细化学反应动力学机理的系统简化方法, 对庚酸甲酯高温燃烧化学动力学机理进行了系统简化. 首先采用两步直接关系图法(Directed relation graph method, DRG)和主成分分析(Principle component analysis, PCA)方法对由1087个物种、4592步可逆反应组成的庚酸甲酯燃烧的详细机理进行框架简化, 得到了包含108个物种, 547步基元反应的框架机理. 在此框架机理基础上, 进一步采用计算奇异值摄动法(Computational singular perturbation, CSP)对框架机理进行时间尺度分析, 再选取30个准稳态物种, 采用准稳态近似(Quasi steady state approximation, QSSA)方法构建了包含78个物种、74步总包反应的全局简化机理. 模拟结果表明, 在较宽的参数范围内, 框架机理和全局简化机理均能重现庚酸甲酯高温燃烧时的点火延迟、物种浓度分布和熄火等燃烧特性. 此外, 基于框架机理阐明了庚酸甲酯高温燃烧的反应路径和对点火有重要影响的基元反应. 与详细机理相比, 框架机理保留了良好的精确性和全局性, 可以很好地反映庚酸甲酯的燃烧特性, 有助于对生物柴油的燃烧过程的理解.     

GRAFT COPOLYMERIZATION OF METHYL ACRYLATE ONTO CHITOSAN INITIATED BY POTASSIUM DIPERIODATONICKELATE (IV)

ABSTRACT

A novel redox system, potassium diperiodatonickelate [Ni (IV)]‐chitosan, was employed to initiate the graft copolymerization of methyl acrylate (MA) onto chitosan in alkali aqueous solution. The effects of reaction variables such as monomer concentration, initiator concentration, reaction time, pH and temperature were determined. By means of a series of copolymerization, the grafting conditions were optimized. The maximum grafting percentage obtained was 404.1% when 0.3 g chitosan was copolymerized with 1.8 mL monomer at 35°C for 5 hours with [Ni (IV)]=9.4×10^?4 M and the total volume was 20 mL. Ni (IV)-chitosan system is found to be an efficient redox initiator for this graft copolymerization. A single electron transfer mechanism is proposed to explain the formation of radicals and the initiation. The grafted copolymers were characterized by IR and X-ray diffraction diagrams. The thermal stability of chitosan and chitosan-g-PMA was studied by thermogravimetric analysis (TGA).     

Benzyl Bromide Functionalized Poly(Phenyleneethynylene)s as Macroinitiators in the Atom Transfer Radical Polymerization of Methyl Methacrylate

Abstract

The behavior of benzyl bromide functionalized poly(phenyleneethynylene)s as macroinitiators in the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was investigated. The ¹H NMR observation of the ATRP using the exclusively para‐linked poly(phenyleneethynylene) macroinitiator PPE1A, and the low molecular weight initiator R‐BzBr, respectively, revealed lower reactivity for the macroinitiator. Comparison of graft copolymers, which were obtained from ATRP of MMA with PPE1A and the partially meta‐linked poly(phenyleneethynylene) PPE1B, showed higher reactivity in the case of PPE1B, expressed by a larger degree of polymerization in the PMMA side chains, as well as higher initiatior efficiency. This might be caused by better solubility of the less symmetric PPE1B. Investigation of the graft copolymers PPE2A and PPE2B was carried out by means of ¹H NMR spectroscopy, gel permeation chromatography (GPC) as well as UV/vis spectroscopy. Impairment of the delocalized π‐electron system of the conjugated polymers during the ATRP was not detectable.     

Influence of Host's Substitution on the Orientation of the Guest: Pseudo-rotaxanes of Charged Cyclodextrins with Methyl Orange in Solution

Methyl Orange (MO), an azo-dye molecule with an inherent dipole moment, has been used as a probe to explore the influence of anionic or cationic substituents of cyclodextrins (CDs) on the mode of insertion to form pseudorotaxanes, using NMR spectroscopy. MO is oriented in a single mode inside the βCD cavity, with the dimethylamino group localized at the secondary side. This orientation is completely reversed when MO enters the anionic sodium heptakis[6-deoxy-6-(3-thiopropionate)]-βCD (βpsp) cavity, whereas inside the cationic heptakis(6-deoxy-6-amino)-βCD hydrochloride, MO flips once more, to adopt the same orientation as in βCD. In the latter case the water solubility of MO is significantly lowered. The disposition of the guest in βCD and in each βCD derivative in a single mode was attributed principally to anti-parallel dipole-dipole stabilization. In the wider γCD, the availability of more cavity space leads to 1:2 and 2:2 host/guest stoichiometries and the effect of dipoles is of secondary significance. In the anionic sodium octakis[6-deoxy-6-(3-thiopropionate)]-γCD, MO is positioned as in βpsp, but a 1:2 adduct is also detected. Finally, MO does not dissolve in octakis(6-deoxy-6-amino)-γCD hydrochloride solution.     

First total synthesis of isoquinolinone alkaloid marinamide and its methyl ester

The first total synthesis of isoquinolinone alkaloid marinamide 1 and its methyl ester 2 was described. The key steps involved a regioselective Frieclel-Crafts reaction of 1-benzyl-1H-pyrrole to form the intermediate 8.     

Synthesis of Methyl N‐Aryl Oxamate Using Soluble Polymer Support

A variety of methyl N‐aryl oxamates were synthesized using poly(ethylene glycol) (PEG) as a soluble polymer support and a monoproctection group with excellent yields.