裂解C_5馏份热二聚制双环戊二烯

采用分段管式反应器进行裂解Ｃ５馏份热二聚反应的研究。通过工艺条件试验，考查了Ｃ５原料中环戊二烯（ＣＰＤ）浓度、各段反应温度、停留时间等对ＣＰＤ转化率、双环戊二烯（ＤＣＰＤ）收率及选择性的影响。以试验数据为依据，建立了描述热二聚反应的数学模型，并对模型中若干参数进行了回归。应用数学模型对该过程的工艺条件进行优化。     

Tetrazine‐Responsive Self‐immolative Linkers

Molecules that undergo activation or modulation following the addition of benign external small‐molecule chemical stimuli have numerous applications. Here, we report the highly efficient “decaging” of a variety of moieties by activation of a “self‐immolative” linker, by application of water‐soluble and stable tetrazine, including the controlled delivery of doxorubicin in a cellular context.     

Preparation of meadowfoam dimer acids and dimer esters,and their use as lubricants

Meadowfoam dimer acids have been prepared in a thermal clay-catalyzed reaction. Reaction conditions have been optimized, and yields of 44% were obtained with 2% water and 6–8% of an acid-washed montmorillonite clay, based on the meadowfoam fatty acids. Purity of the distilled dimer acids was 79–89% with most of the remaining 11–22% being residual mono- and tribasic acids. Dimethyl, di-(2-ethylhexyl), and di-n-butyl meadowfoam dimer ester derivatives were also prepared. Color, viscosity, and wear-preventive characteristics of the meadowfoam dimer acids and dimer ester derivatives were compared to those of commercial dimer acids and dimer esters. The viscosity of the meadowfoam dimer acids is similar to that of Empol® 1010, which is also derived from a highly monounsaturated fatty acid source. Viscosities of the meadowfoam dimer esters were also comparable to those of commercial dimer esters. Wear prevention characteristics, as determined by the four-ball test method, of the meadowfoam dimer acids and dimer esters were similar to those of the commercial products. In one case, the di-n-butyl esters, the meadowfoam derivative showed a significantly smaller wear scar than that shown by the di-n-butyl derivative of Unidyme® 14.     

Removable foams based on an epoxy resin incorporating reversible Diels–Alder adducts

We have successfully incorporated Diels–Alder reversible chemistry into epoxy resins. The Diels–Alder chemistry goes in the forward direction at 60 °C and reverses at or above 90 °C. One resin was formulated with other commercial ingredients into foamed epoxy. The foam, shown to have mechanical properties similar to foams formed with conventional epoxy resins, is being utilized for electronic encapsulation. Because of the built‐in reversible chemistry, the foams can be easily removed by dissolution in 1‐butanol at 90 °C. Removal allows for the rework, upgrading, or dismantlement of the electronic components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1496–1502, 2002     

电子相互作用对纳米石墨带中二聚化的影响

对Peierls-extended Hubbard模型和Hartree-Fock模型进行近似分析，研究了纳米石墨带中电子相互作用对二聚化的影响．结果表明：在位电子相互作用几乎总是抑制二聚化，而适当大小的位间电子相互作用则有利于二聚化．由于电-声相互作用与电子相互作用之间的竞争，带宽越大的石墨带中越有可能出现更大的二聚化．     

Mechanism Controlling High-Temperature Degradation of Sunflower Oil Triacylglycerols in the Absence of Oxygen

The aim of the present study is to describe the mechanism controlling heat-induced formation of sunflower oil triacylglycerol and fatty acid methyl ester oligomers. The unique combination of high-performance size-exclusion chromatography with hyphenated electrospray ionization mass spectrometry (MS), atmospheric pressure chemical ionization-MS, and high-temperature gas chromatography-MS techniques allows differentiating between radical coupling species and Diels–Alder cycloadducts. Targeted analysis of thermally degraded sunflower oils confirms the exact structures of various acyclic oligomers accompanied by less-abundant products of pericyclic transformations. A series of model experiments simulate the impact of dienophile nature on the course of Diels–Alder reactions. Thus, α-tocopherylquinone, δ-tocopherylquinone, and methyl-(E)-11-oxoundec-9-enoate are synthesized as naturally occurring dienophiles bearing electron-withdrawing groups. The geometry of poor dienophiles does not affect concerted cyclization, while the structure of electron deficient dienophiles can overcome low reactivity. Practical Application: In the absence of oxygen, heat-induced degradation of polyunsaturated triacylglycerols proceed predominantly via a radical pathway, whereas concerted reactions represent minor mechanisms. Sunflower oil triacylglycerol molecules in the system without propagation stage can be effectively protected by natural and/or synthetic antioxidants. Application of chelates is also recommended. However, antioxidant-derived quinones, such as α-tocopherylquinone, can enter the Diels–Alder reaction even more easily than dienophiles without electron-withdrawing groups. Unsaturated core aldehydes possess the same reactivity. Examination of the mechanism controlling high-temperature degradation of triacylglycerols is especially important for processing engineers in edible oil refineries and food technologists. New perspective may help them to minimize undesirable changes in polyunsaturated species.     

Chiral Synthesis on Catalysts Immobilized in Microporous and Mesoporous Materials

Abstract

This paper reviews the recent progress made in the asymmetric synthesis on chiral catalysts in porous materials and discusses the effects of surface and pores on enantioselectivity (confinement effect). This paper also summarizes various approaches of immobilization of the chiral catalysts onto surfaces and into pores of solid inorganic supports such as microporous and mesoporous materials. The most important reactions surveyed for the chiral synthesis in porous materials include epoxidation, hydrogenation, hydroformylation, Aldol and Diels‐Alder reactions, etc. The confinement effect originated from the surfaces and the pores turns out to be a general phenomenon, which may make the enantioselectivity increase (positive effect) or decrease (negative effect). The confinement effect becomes more pronounced particularly when the bonding between the catalyst and the surface is more rigid and the pore size is tuned to a suitable range. It is proposed that the confinement in chiral synthesis is essentially a consequence of subtle change in transition states induced by weak interaction in pores or on surfaces. It is also anticipated that the enantioselectivity could be improved by tuning the confinement effect based on the molecular designing of the pore/surface and the immobilized catalysts according to the requirements of chiral reactions.     

Asymmetric membranes by wet phase inversion of phenylated polyphenylene

Asymmetric membranes of phenylated polyphenylene were prepared by wet phase inversion. The polyphenylene (M_n = 62 kDa, PD = 2.3) was prepared by Diels–Alder polymerization of 1,4‐bis(tetraphenylcyclopentadienonyl)benzene with 1,4‐diethynylbenzene at 180°C. Solvents and non‐solvents were experimentally identified and solvent : non‐solvent systems were evaluated by the quality of the resulting membranes. Cyclohexanone/n‐butanol (88 : 12) as solvent and n‐butanol as the non‐solvent were found to afford the best asymmetric membranes with minimal defects. Membranes (20–30 µm thick) from coagulating 11.5 wt % polyphenylene from cyclohexanone/n‐butanol in n‐butanol baths exhibited 250–300 nm, non‐porous skins overlaying 20–30 µm of open‐celled, spongiform structure. Due to a relatively high glass transition temperature of 370°C, the phenylated polyphenylene membranes retained their porosity to 200°C higher than polysulfone asymmetric membranes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biosynthetic Pathways of Dimeric Natural Products Containing Bisanthraquinone and Related Xanthones

Many dimeric natural products containing bisanthraquinone and related xanthones with diverse structures and versatile bioactivities have been isolated over the years. However, the complicated biosynthetic pathways of such natural products, which have remained elusive until recently, negatively impact their mass bioproduction and biosynthetic structural modification for drug discovery. In this concept, we summarize the recent progress in gene cluster mining and biosynthetic pathway elucidation of natural products containing bisanthraquinone and related xanthones. These pioneering works may pave the way for further biosynthetic pathway elucidation and structure modification of dimeric natural products through gene and protein engineering.