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1.
利用各种芳基格氏试剂与四氟乙烯在四氢呋喃中的反应,合成了六个取代三氟苯乙烯,其中取代基分别为:p-CH_3O,p-CH_3,m-CH_3,p-Cl,m-Cl和m-CF_3,还合成了α-与β-三氟萘乙烯. 研究了在已合成的取代三氟苯乙烯化合物(1)中取代基的电子效应对~(19)F NMR参数的影响.建立了取代基的Hammett常数σ分别与下列~(19)F NMR参数间的线性相关关系;化学位移δ(F~1)-δ(F~2)、偶合常数J_12及化学位移之差Δδ_(3-1)=δ(F~3)-δ(F~1)(或者Δδ_(3-2),证实了过去的预计.建议以Δδ_(3-1)值作为衡量三氟乙烯类化合物中π键极化程度的尺度.并把这一定量的“歪电子云”概念与有关的化学事实联系起来. 相似文献
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对脂环化合物立体异构相关的4个问题进行了分析和归纳,包括手性碳的判断、是否存在对映异构体、手性碳R/S构型标记以及立体异构体数目的确定等。 相似文献
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含硅氧烷结构聚酰亚胺树脂的耐热稳定性及高温结构演变 总被引:1,自引:0,他引:1
基于含硅芳香二胺双(4-氨基苯氧基)二甲基硅烷(APDS)设计制备了系列苯乙炔基封端的含硅氧烷结构聚酰亚胺树脂预聚物(PEPA-PIS), 考察了硅氧烷含量对树脂固化物耐热稳定性的影响规律. 利用非反应性苯酐基团封端的模型预聚物(PA-PIS)证明了温度对于硅氧烷结构演变的影响. 通过对树脂固化物高温固化处理后耐热稳定性与微观结构和表面形貌的关系进行深入研究, 发现在高温下硅氧烷结构发生氧化交联反应, 并在树脂表面形成具有无机特性的二氧化硅结构, 这种有机/无机杂化特性可显著提高聚酰亚胺树脂的耐热稳定性. 相似文献
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长链全氟烷基化合物的~(19)F NMR化学位移已有很多报道,然而,文献报道的大多是CF_3-(CF_2)_n-X化合物,对于X-(CF_2)_n-Y化合物报道相对较少。长链全氟烷基化合物的~(19)F NMR谱的归属是较困难的,特别是对于X-(CF_2)_n-Y的化合物的谱,由于两端取代基的效应,图谱归属更困难。本文报道一些未报道过的长链全氟烷基化合物的~(19)F NMR化学位移的数据,并讨论它们的归属。 相似文献
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F. Crea R. Mostowicz F. Testa R. Aiello A. Nastro J. B. Nagy 《Journal of Thermal Analysis and Calorimetry》1992,38(4):693-700
By means of simultaneous DTA-, TG- and DTG-technique, the silicate gels and the MFI crystals obtained from these gels have been investigated. The gels have been prepared in presence and in absence of tetrapropylammonium cation (TPA+) and with Li+, Na+, NH
4
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and K+ fluorides. In absence of TPA+ no thermal effects have been observed in Li+- and Na+-gels. The effects observed in the NH
4
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-gel stem from a decomposition and release of inorganic phases: SiF4, NH4F, NH3. The DTA/DTG effects in the TPA+ containing gels and in the MFI crystals of monodisperse size are attributed to the decomposition of TPA+ cation. It can be concluded from these effects that the interaction between the gels and the TPA+ cation is rather weak. The interaction between TPA+ and MFI crystals obtained in fluoride medium is stronger than the interaction with crystals obtained from alkaline media. Similar thermal effects are obtained after grinding the long crystals to those having a large distribution of crystal sizes.
Zusammenfassung Mittels simultaner DTA-, TG- und DTG-Techniken wurden Kieselgele und die MFI-Kristalle dieser Gele untersucht. Die Gele wurden in und ohne Gegenwart von Tetrapropylammoniumkationen (TPA+) und mit Li+-, Na+-, NH 4 – und Kaliumfluoriden hergestellt. Bei Abwesenheit von TPA+ werden für Li+- und Na+-Gele keine thermischen Effekte beobachtet. Der bei NH 4– -Gelen beobachtete Effekt ergibt sich aus der Zersetzung und Abspaltung von anorganischen Phasen: SiF4, NH4F, NH3. Die DTA/DTG-Effekte in TPA+-haltigen Gelen und in den MFI-Kristallen monodispersen Ausmaes werden der Zersetzung des TPA+-Kations zugeschrieben. Daraus kann man schlieen, da die Wechselwirkung zwischen den Gelen und dem TPA+-Kation eher schwach ist. Die Wechselwirkung zwischen TPA+ und MFI-Kristallen aus fluoridischen Medien ist strker als die Wechselwirkung mit Kristallen aus alkalischen Medien. Ähnliche thermische Effekts erhlt man, nachdem man die langen Kristalle zerkleinert und eine breite Kristallgrenverteilung erhlt.相似文献
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Yousuke Konno Hiroto Kudo Atsushi Kameyama Tadatomi Nishikubo 《Journal of polymer science. Part A, Polymer chemistry》2004,42(10):2543-2550
Fluorine‐containing polyethers with pendant hydroxyl groups were synthesized by the polyaddition of fluorine‐containing bis(epoxide)s with certain fluorine‐containing diols with quaternary onium salts as catalysts. When the polyaddition was performed with 2,2′,6,6′‐tetrafluoro‐4,4′‐biphenol diglycidiyl ether and 2,2′,6,6′‐tetrafluoro‐4,4′‐biphenol, the corresponding polyether with pendant hydroxyl groups was successfully obtained in good yield. The polyaddition of certain fluorine‐containing bis(epoxide)s with diols also proceeded in bulk to provide the corresponding fluorine‐containing polyethers with high molecular weights. These polyethers were highly transparent at 157 nm for 0.1 μm thickness, with their transmittance of 14–75% at 157 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2543–2550, 2004 相似文献
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用国标GB7483-87《水质氟化物的测定氟试剂分光光度法》不能准确测定氟碳铈矿中的氟量.原因在于该氟碳铈矿中的氟量比较高,一般达到9%~11%,易形成REF3沉淀,用一般的酸消解法很难将氟从矿样中全部蒸馏出来.本文采用加入Ca(OH)2,使氟转化CaF2,矿中的氟能完全被蒸出.并做了矿中氟测定的精密度实验,矿中的氟质量分数为9.02%,CV=0.4424.经加标矿中氟量的0.5、1和2倍等3个水平,其回收率在97.83%~99.44%范围,方法是对国标测氟法的重要补充. 相似文献
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General purpose poly(styrene) prepared by conventional radical techniques contains a head-to-head unit as a consequence of
polymerization termination by radical coupling. As has been previously demonstrated, thermal stress promotes homolysis of
the bond linking the head-to-head components. The macroradicals generated depolymerize rapidly to generate styrene monomer.
This decomposition during processing can lead to finished articles containing objectionable levels of styrene monomer, particularly
for food packaging applications in which even low levels of monomer can promote objectionable taste and aroma. Polymer containing
no head-to-head units should not be prone to this facile decomposition. In this instance, poly(styrene) has been prepared
by nitroxyl-mediated polymerization of styrene monomer followed by reductive removal of nitroxyl end groups. Polymer prepared
in this manner contains no head-to-head units and displays thermal stability much greater than that observed for conventional
poly(styrene). A direct comparison of the stability for the two polymers is readily available by thermogravimetric techniques.
A quantitative reflection of the difference in stability is available from the rate constants for the respective decomposition. 相似文献
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Jung S. Shim Joseph P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》2000,38(2):279-290
Novel thermoplastic elastomers (TPEs) consisting of poly(isobutylene‐b‐indene) (PIB‐b‐PInd) arms radiating from hexamethylcyclohexasiloxane (D) cores were prepared, characterized, and their properties investigated. The syntheses of these star‐blocks involved the linking by hydrosilation of PInd‐b‐PIB CH2 CHCH2 prearms to D. The prearms were obtained by initiating the living polymerization of Ind by the cumyl chloride (CumCl)/TiCl4 or cumyl methoxide (CumOMe)/TiCl4 systems, continuing by the sequential block copolymerization of IB, and concluding the synthesis by end quenching with allyltrimethylsilane (ATMS). Dedicated experiments were carried out to develop conditions for the various synthesis steps. Select mechanical, thermal, and rheological properties of TPE star‐blocks having 5–18 PInd‐b‐PIB arms have been investigated. Because of the high Tg of the glassy PInd segment (Tg,PInd = 170–220°C), these TPEs maintained their strength at higher temperatures than those of similar polystyrene‐based star blocks. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 279–290, 2000 相似文献
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This review covers our extensive research activities in the area of fluorine containing phospha- and arsaalkenes as well as selenocarbonyls, which differ considerably in their properties and reactivities from their alkyl and aryl counterparts and thus contribute in a gratifying manner to the still growing field of unsaturated element-carbon compounds of 3rd and 4th row main group elements E. Of particular interest is the influence of the fluorine substituents and other small groups (OR, NR2) with either inductive and/or mesomeric effects on the polarity and reactivity of the EC bond. Addition reactions of proton acidic and hydridic polar HX reactants as well as [2+2], [3+2] and [4+2] cycloadditions have been thoroughly studied. The results obtained allow a classification of the EC systems within five different types, A to E, and prove a change from “normal” to “inverse” heteroalkenes in this sequence. The ligand properties of some derivatives have also been investigated in some detail. 相似文献
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Tengjiao Hu Chengqing Wang Fuming Li Frank W. Harris Stephen Z. D. Cheng Chi Wu 《Journal of Polymer Science.Polymer Physics》2000,38(16):2077-2080
Eight 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride‐4,4′‐diamino‐3,3′‐dimethylbiphenyl (6FDA‐OTOL) fractions and seven 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy) phenyl] propane dianhydride‐4,4′‐diamino‐3,3′‐dimethylbiphenyl (BISADA‐OTOL) fractions in cyclopentanone at 30 °C were characterized by a combination of viscometry and static and dynamic laser light scattering (LLS). In static LLS, the angular dependence of the absolute scattered intensity led to the weight‐average molar mass (Mw), the z‐average root mean square radius of gyration, and the second virial coefficient. In dynamic LLS, the Laplace inversion of each measured intensity–intensity time correlation function resulted in a corresponding translational diffusion coefficient distribution [G(D)]. The scalings of 〈D〉 (cm2/s) = 8.13 × 10−5 Mw−0.47 and [η] (dL/g) = 2.36 × 10−3 Mw0.54 for 6FDA‐OTOL and 〈D〉 (cm2/s) = 3.02 × 10−4 Mw−0.60 and [η] (dL/g) = 2.32 × 10−3 Mw0.53 for BISADA‐OTOL were established. With these scalings, we successfully converted each G(D) value into a corresponding molar mass distribution. At 30 °C, cyclopentanone is a good solvent for BISADA‐OTOL but a poor solvent for 6FDA‐OTOL; this can be attributed to an ether linkage in BISADA‐OTOL. Therefore, BISADA‐OTOL has a more extended chain conformation than 6FDA‐OTOL in cyclopentanone. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2077–2080, 2000 相似文献
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Synthesis of fluorine containing glycolurils and oxazolines from oxides of internal perfluoroolefins
Lyudmila V. Saloutina Aleksandr Ya. Zapevalov Victor I. Saloutin Pavel A. Slepukhin Mikhail I. Kodess Oleg N. Chupakhin 《Journal of fluorine chemistry》2009,130(10):853-860
The reaction of oxides of internal perfluoroolefins 1-3 with urea gave two kinds of novel fluorine containing N-heterocyclic compounds depending on the solvent nature: 1,5-bis(perfluoroalkyl)tetraazabicyclo[3.3.0]octane-3,7-diones 4a-c and 2-amino-5-fluoro-4,5-bis(perfluoroalkyl)-4,5-dihydrooxazol-4-ols 7a-d. Use of polar dimethylsulfoxide, N,N-dimethylacetamide and acetonitrile afforded glycolurils 4a-c in moderate yields. In dioxane, unexpected cyclization occurred resulting in oxazolines 7a-d in high yields. A similar reaction of oxiranes 2, 3 with urea in aqueous dioxane gave mixtures of 4,5-dihydroxy-4,5-bis(perfluoroalkyl)imidazolidine-2-ones 9b, c, glycolurils 4b, c and oxazolines 7b-d. The molecular structure of trans-isomers of oxazoline 7b and imidazolidine 9b has been established by X-ray crystallography. 相似文献
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The novel cationic polyacrylate latex containing fluorine silicon was successfully prepared via soap-free emulsion polymerization of butyl acrylate, methyl methacrylate, vinyltriethoxysilane and hexafluorobutylmethacrylate in water phase, which were initiated with water soluble azo initiator and emulsified with the mixed surfactants polymerizable emulsifier and OP-10. The films of the resultant latex were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA) determinator, respectively. In comparison with the conventional polyacrylate latex, the thermal stability and water resistance of novel latex film are improved. The conditions of preparing the novel cationic acrylate latexes were optimized. The optimum conditions of preparing the novel latex are as follows: the amount of emulsifiers and the initiator are 6.0% and0.3%, respectively; both the amount of VETS and amount of HFMA are 6.0%. In this case, the conversion is high and the polymerization stability is good. 相似文献