A Kinetic Evidence for the Nitroxyl Radicals Recycling Mechanism in the Photostabilizing Process of HALS

The photoinduced bulk polymerization of a reactive-hindered amine fight stabilizers(r-HALS), 4-acryloyl-2, 2, 6, 6-tetramethylpiperidinyl (ATMP), was performed at 80℃ by using a DPC technique. An unique periodic exponential attenuation-type oscillating curve was found when the polymerization was carried out in air, but this phenomenon was not found in nitrogen.It is supposed that this unique kinetic performance may be attributed to nitroxyl radicals that are produced in situ from the oxidation of ATMP. ATMP polymer with narrow polydispersity (d =1.03) can be obtained by photoinduced solution polymerization of ATMP. The signal detected in ESR may be assigned to the nitroxyl radicals in the matrix of ATMP polymer. Since this kind of recycling of nitroxyl radicals is well documented for the photostabilizing mechanism of HALS, the present results may serve as a kinetic evidence for this mechanism.     

ATOMIC FORCE MICROSCOPY STUDIES OF POLYCAPROLACTONE RINGED SPHERULITES*

The surface morphology of free-surface PCL ringed spherulites was investigated by using atomic forcemicroscopy. The spherulites were obtained by crystallization of PCL/PVC blends of different compositions. It was found thatthe ringed spherulite exhibited regularly fluctuating rings on its surface. Compared with the bright-dark ring pattern of thespherulite under a polarizing microscope, it was proved that the optical characteristics of the ringed spherulite underpolarizing microscope coincided with its surface characteristics. The bright rings in polarizing micrographs of the spherulite coincided with the convex rings on its surface, while the dark rings coincided with the concave rings.     

A novel trilinear decomposition algorithm： Three-dimension non-negative matrix factorization

Non-negative matrix factorization(NMF)is a technique for dimensionality reduction by placing non-negativity constraints onthe matrix.Based on the PARAFAC model,NMF was extended for three-dimension data decomposition.The three-dimension non-negative matrix factorization(NMF3)algorithm,which was concise and easy to implement,was given in this paper.The NMF3algorithm implementation was based on elements but not on vectors.It could decompose a data array directly without unfolding,which was not similar to that the traditional algorithms do.It has been applied to the simulated data array decomposition andobtained reasonable results.It showed that NMF3 could be introduced for curve resolution in chemometrics.     

Prediction of retention indexes. I. Structure-retention index relationship on apolar columns

A simple method is reported for predicting the retention index (RI) of a chemical compound from the number of carbon and carbon equivalent atoms in the molecule, the RI increment for atom addition and the group retention factors (GRFs) for substituents and functional groups. Atoms other than carbon such as oxygen, nitrogen, sulfur, chlorine, bromine and iodine are assigned carbon atom equivalency of approximately 1, 1, 2, 2, 3 and 4, respectively and are counted for their contribution towards RI prediction. The GRFs of substituents and functional groups are derived from the RIs of reference compounds and series of homologues. Ring structures, ring fusion, ring connection, iso- and neo-carbons, chain branching and unsaturation are also assigned GRFs. The predicted RIs of a number of alicyclic, aliphatic and aromatic hydrocarbons, primary, secondary and tertiary alcohols, phenols, aliphatic amines, aromatic amines, heterocyclics, carboxylic acids, acid esters, aldehydes, ketones, and halogenated compounds, are found to be within +/- 3% of the observed values. The structure-retention index relationship thus developed is extremely useful in the tentative identification of radioactive side products formed in tritium labeling by radiation-induced methods.     

Theoretical studies of mechanisms of cycloaddition reaction between difluoromethylene carbene and acetone

Mechanisms of the cycloaddition reaction between singlet difluoromethylene carbene and acetone have been investigated with the second‐order Møller–Plesset (MP2)/6‐31G* method, including geometry optimization and vibrational analysis. Energies for the involved stationary points on the potential energy surface (PES) are corrected by zero‐point energy (ZPE) and CCSD(T)/6‐31G* single‐point calculations. From the PES obtained with the CCSD(T)//MP2/6‐31G* method for the cycloaddition reaction between singlet difluoromethylene carbene and acetone, it can be predicted that path B of reactions 2 and 3 should be two competitive leading channels of the cycloaddition reaction between difluoromethylene carbene and acetone. The former consists of two steps: (i) the two reactants first form a four‐membered ring intermediate, INT2, which is a barrier‐free exothermic reaction of 97.8 kJ/mol; (ii) the intermediate INT2 isomerizes to a four‐membered product P_2b via a transition state TS2b with an energy barrier of 24.9 kJ/mol, which results from the methyl group transfer. The latter proceeds in three steps: (i) the two reactants first form an intermediate, INT1c, through a barrier‐free exothermic reaction of 199.4 kJ/mol; (ii) the intermediate INT1c further reacts with acetone to form a polycyclic intermediate, INT3, which is also a barrier‐free exothermic reaction of 27.4 kJ/mol; and (iii) INT3 isomerizes to a polycyclic product P₃ via a transition state TS3 with an energy barrier of 25.8 kJ/mol. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

羟基铝溶液及铝交联蒙脱土的研究

本文用(27)~Al NMR法和8-羟基喹啉萃取法分别研究了羟基铝溶液中十三聚铝含量的变化规律,还用X-射线衍射法研究了铝交联蒙脱土d_(001)的变化。研究结果表明,铝离子的聚合情况主要由羟铝比决定,而浓度影响不大。随着羟铝比的增加,溶液中单核铝离子含量减少,十三聚铝离子相对含量增加,所得铝交联蒙脱土的d_(001)也随之增大。参照这些变化规律、控制羟基铝溶液的组成,可以制备各种层柱状铝交联蒙脱土复合物。     

二碘化钐作用下缺电子烯烃的还原偶联反应

室温下SmI2-HMPA-t-BuOH-THF体系能顺利地将丁烯二酸二酯还原偶联为1, 2, 3, 4-四烷氧基羰基丁烷, 同样条件下, 亚苄基氰乙酸乙酯,α-乙氧羰基肉桂酸乙酯, α-乙酰基肉桂酸乙酯和亚苄基丙二酸亚异丙酯等化合物也发生还原偶联反应得到相应的二聚体。     

新型手性Salen双核锌配合物的分子识别研究

合成了新型手性Salen配体（H3L）及新型手性Salen双核锌配合物（主体）.通过研究主体对咪唑类客体及氨基酸酯类客体的分子识别行为,测定了这些配位反应的缔合常数.主体对咪唑类客体分子识别的缔合常数顺序为:K(Im) >K(2-MeIm) >K(2-Et-4-MeIm).主体对氨基酸酯类客体分子识别的缔合常数顺序为:K(LeuOCH3) >K(ValOCH3) >K(AlaOCH3) >K(SerOCH3),配位数均为2.主体与D、 L型氨基酸酯分子识别反应在不同温度下的缔合常数结果表明,随着温度的升高,对映选择性下降.实验发现反应体系中存在焓熵补偿关系. CD光谱的研究结果也反映了主体对不同客体识别能力的差异.     

不对称Salen-Mn(Ⅲ)配合物催化PNPP水解的动力学研究

用分光光度法研究了两种不对称Salen-Mn(Ⅲ)配合物催化α-吡啶甲酸对硝基苯酚酯(PNPP)的水解动力学.提出了相应的PNPP催化水解机理,讨论了底物浓度、体系的酸碱度、温度以及配合物结构对PNPP催化水解反应的影响.结果表明:此两种Schiff碱锰(Ⅲ)配合物在催化PNPP水解中均表现出较好的催化活性,PNPP水解速率随着底物浓度、体系pH值的增大而增大;在15～55℃温度范围内,未观察到催化剂失活现象;其中,带有苯并氮杂-15-冠-5侧基的不对称Salen-Mn(Ⅲ)配合物比带有吗啉基的另一配合物拥有更高的催化活性,这可能主要由这两种模拟水解酶之间较大的疏水微环境差异所引起.