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991.
Dae Woo Ihm Soo Young Park Cheol Gyu Chang Yoon Sung Kim Hwan Kwang Lee 《Journal of polymer science. Part A, Polymer chemistry》1996,34(14):2841-2850
The effects of transesterification on the miscibility of poly(ethylene terephthalate)/poly(ethylene 2,6-naphthalate) were studied. Blends were obtained by solution precipitation at room temperature to avoid transesterification during blend preparation. The physical blends and transesterified products were analyzed by wide-angle x-ray scattering, differential scanning calorimetry, and nuclear magnetic resonance spectroscopy. It was found that the physical blends are immiscible and when the extent of transesterification reaches 50% of the completely randomized state, independent of blend composition, the blends are not crystallizable and show a single glass transition temperature between those of starting polymers. The interchange reactions were significantly influenced by annealing temperature and time but negligibly by blend composition. © 1996 John Wiley & Sons, Inc. 相似文献
992.
异核双金属有机化合物的合成方法与反应性能研究 总被引:1,自引:0,他引:1
本文对近年来异核双金属有机化学的发展作了简要的介绍和回顾, 文中对含金属-金属键和不含金属-金属键的d/d和d/f异核双金属有机化合物的合成方法及反应性能作了归纳。 相似文献
993.
Hao-Ming Jeng Chung-Zen Tsai Tsu-Yen Chang 《Fresenius' Journal of Analytical Chemistry》1990,338(8):902-904
Summary The composition and stability of copper(I) complexes with thioacetamide (TAA) have been evaluated with the help of square-wave voltammetry using the fast pulse technique. Two species, namely Cu(I) (TAA) and Cu(I) (TAA)2, have been identified having the formation constants log 1=16.85; log 2=18.03. The complex is stable in highly acidic medium (pH1). The application for the determination of copper is pointed out. 相似文献
994.
Based on the “2-phenyinaphthalene-type” structural pattern hypothesis, a number of heterocycle-fused anthraquinones were designed by taking morindaparvin-A ( 2a ) as the lead structure. The compounds we synthesized and tested for antineoplastic activity include 1,2-alkylenedioxyanthraquinone, naphtho [2,3-f]-quinoxaline-7,12-dione, anthra[1,2-d]imidazole-6,11-dione and naphtho[2,3-f]quinoxaline-7,12-dione derivatives. Most of the synthesized anthraquinones possessed various degrees of anticancer activity. One of these compounds, 2-chloromethyl-1H-anthra[1,2-d]imidazole-6,11-dione ( 4b ), exhibited cytotoxic activity against all tested human carcinoma cell lines. 相似文献
995.
A seven-membered ketolactone, tanshinketolactone (1), was isolated from the root of Salvia miltiorrhiza. Its structure was established by spectroscopic analysis. 相似文献
996.
A new N-fatty acyl tryptamine, cheritamine ( 30 ), along with thirty-two compounds including nineteen benzenoids, p-hydroxybenzadehyde ( 1 ), p-hydroxybenzoic acid ( 2 ), methylparabene ( 3 ), 3-chlorobenzoic acid ( 4 ), vanillin ( 5 ), isovanillin ( 6 ), vanillic acid ( 7 ), isovanillic acid ( 8 ), methyl vanillate ( 9 ), methyl isovanillate ( 10 ), syringaldehyde ( 11 ), syringic acid ( 12 ), 3,4,5-trimethoxybenzoic acid ( 13 ), trans-methyl p-coumarate ( 14 ), ferulic acid ( 15 ), p-dihydrocoumaric acid ( 16 ), 3-(4-hydroxy-3,5-dimethoxyphenyl)-1,2-propanediol ( 17 ), 3,4,5 -trimethoxyphenyl-β-D-glucopyranoside ( 18 ) and thalictoside ( 19 ); one p-quinone, 2,6-dimethoxy-p-quinone ( 20 ); one purine, uridine ( 21 ); eight alkaloids, nicotinic acid ( 22 ), thalifoline ( 23 ), doryphornine ( 24 ), (–)-norstephalagine ( 25 ), (-)-romucosine ( 26 ), (+)-pronuciferine ( 27 ), (+)-norisocorydine ( 28 ) and oxoasimilobine (29) and three steroids, β-sitosterol-D-glucoside ( 31 ), stigmasterol-D-glucoside ( 32 ) and 6′-(β-sitosteryl-3-O-β-glucopyranosidyl)hexadecanoate ( 33 ), are isolated from the stems of Annona cherimola. These compounds were characterized and identified by physical and spectral evidence. 相似文献
997.
Jyh-Horng Sheu Kuie-Chi Chang Ping-Jyun Sung Chang-Yih Duh Ya-Ching Shen 《中国化学会会志》1999,46(2):253-257
A new marine sterol 7β-hydroperoxy-24-methylenecholesterol ( 1 ) along with five known compounds sarcophytol A ( 2 ), (Z)-N-[2-(4-hydroxyphenyl)ethyl]-3-methyldodec-2-enamide ( 3 ), 5α,7αH-eduesm-11(13)en-4α-ol ( 4 ), 24-methylenecholesterol ( 5 ) and 1β-hydroxy-α-cyperone ( 6 ) have been isolated from a Formosan soft coral Sinularia sp. The structures of the above compounds were determined by spectral analyses. Cytotoxicity of compounds 1–6 toward various cancer cell lines also is reported. 相似文献
998.
Shih‐Jieh Sun Gert Schwarz Hans R. Kricheldorf Teh‐Chou Chang 《Journal of polymer science. Part A, Polymer chemistry》1999,37(8):1125-1133
Several binary copolycarbonates were prepared by polycondensation of 2,5‐bis(4‐hydroxybenzylidene)cyclopentanone, BHBC, with methylhydroquinone, MHQ, hydroquinone 4‐hydroxybenzoate, HQHB, or isosorbide. Furthermore, five ternary copolycarbonates were prepared based on the aforementioned monomers. All polycondensations were conducted in pyridine with trichloromethyl chloroformate as condensing agent. All polycarbonates were characterized by elemental analyses, viscosity and DSC measurements, IR and 1H‐ and 13C‐NMR spectroscopy, optical microscopy, and the WAXS powder pattern. All isosorbides containing binary and ternary copolycarbonates were found to form a cholesteric melt, but only three of them were capable to form a stable Grandjean texture upon shearing. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1125–1133, 1999 相似文献
999.
Ansa‐zirconocene diamide complex rac‐(EBI)Zr(NMe2)2 [rac‐1, EBI = ethylene‐1,2‐bis(1‐indenyl)] reacted with AlR3 (R = Me, Et, iBu) or Al(iBu2)H and then with [CPh3][B(C6F5)4] (2) in toluene in order to perform propylene polymerization by cationic alkylzirconium species, which are in situ generated during polymerization. Through the sequential NMR‐scale reactions of rac‐1 with AlR3 or Al(iBu2)H and then with 2, rac‐1 was demonstrated to be transformed to the active alkyzirconium cations via alkylated intermediates of rac‐1. The cationic species generated by using AlMe3, AlEt3, and Al(iBu2)H as alkylating reagents tend to become heterodinuclear complex; however, those by using bulky Al(iBu)3 become base‐free [rac‐(EBI)Zr(iBu)]+ cations. The activity of propylene polymerization by rac‐1/AlR3/2 catalyst was deeply influenced by various parameters such as the amount and the type of AlR3, metallocene concentration, [Al]/[2] ratio, and polymerization temperature. Generally the catalytic systems using bulky alkylaluminum like Al(iBu)3 and Al(iBu)2H show higher activity but lower stereoregularity than those using less bulky AlMe3 and AlEt3. The alkylating reagent Al(iBu)3 is not a transfer agent as good as AlMe3 or AlEt3. The polymerization activities show maximum around [Al]/[2] ratio of 1.0 and increase monotonously with polymerization temperature. The overall activation energy of both rac‐1/Al(iBu)3/2 and rac‐1/Al(iBu)2H catalysts is 6.0 kcal/mol. As the polymerization temperature increases, the stereoregularity of the resulting polymer decreases markedly, which is demonstrated by the decrease of [mmmm] pentad value and by the increase of the amount of polymer soluble in low boiling solvent. The physical properties of polymers produced in this study were investigated by using 13C‐NMR, differential scanning calorimetry (DSC), viscometry, and gel permeation chromatography (GPC). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1523–1539, 1999 相似文献
1000.
Lee Soon Park Tae Hyung Lee Soo Chang Lee 《Journal of polymer science. Part A, Polymer chemistry》1999,37(14):2311-2317
Copolymerizations of p-dichlorobenzene (DCB)/4-bromophenyl ether (BPE), DCB/4,4′-dibromobiphenyl (DBB), and DBB/BPE pairs with sodium sulfide under high temperature (270–290°C) utilizing N-methyl-2-pyrrolidinone (NMP) as solvent were carried out to give C(DCB/BPE), C(DCB/DBB), and C(DBB/BPE) copolymers, respectively. The reactivity of dihaloaromatic monomers toward thiolate anion in the polycondensation reaction followed the order DBB > DCB > BPE. The reactivity gap between DBB and DCB toward thiolate anion seemed to be smaller than that between BPE and DCB, resulting in both high yield and high molecular weight in the C(DCB/DBB) copolymers compared to C(DCB/BPE) copolymers. The copolymerization of DBB/BPE pair with sodium sulfide, which has larger reactivity gap than the DCB/DBB or DCB/BPE pair, gave mixtures of PBS and PPSE homopolymers especially in the range of 50–80 mol % BPE in the feed. The C(DCB/DBB) and C(DCB/BPE) copolymers, however, exhibited random copolymer character in all comonomer ratios in the feed as evidenced by copolymer composition and DSC data. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2311–2317, 1999 相似文献