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151.
ExtensivestudiesofradiationorchemicalinjuryofbiologicaltargetmoleculesdemonstratethatOHradical,themostreactiveoxygenspecies,reactswithbiologicalmacromolecules,suchasDNA,inducingbasealterations,basicsites,andstrandbreaks,resultedinvariouspathogenesis,such… 相似文献
152.
The Pd(0)-catalyzed coupling reaction of electron-deficient alkenyl halides with the organozinc formed by the subsequent treatment of 1-phenylalk-1-yne with n-BuLi and ZnBr2 with or without a catalytic amount of HgCl2 was studied. Both the allene-formation- and the alkyne-formation-type coupling reactions were observed with high regio- and stereoselectivity: the reaction of 1-phenylprop-1-yne afforded 6-phenylhex-5-yn-2(or 3)-enoates and -enitriles, while the reaction of 1-phenylhex-1-yne formed 4-phenyl-6-substituted-hexa-2,4,5-trienoates. A plausible explanation for the regioselectivity was discussed. The double bonds in 6-phenylhex-5-yn- 2-enoates were prone to migrate to the position conjugated with the carbon-carbon triple bonds to form 6-phenylhex-5-yn-3-enoates at higher temperature. The migration did not occur in absence of an excess amount of allenic/propargylic zinc reagent or at low temperature. 相似文献
153.
Summary A colorimetric method for the determination of phenolic compounds containing the nitro function is described. It is based on the production of a yellow color when nitrophenols are treated with iminobispropylamine in monochlorobenzene solution. There is no interference due to the presence of carbonyl and carboxyl groups in the molecule. Relationship between absorbance and concentration is linear in the range of 1 to 20g/ml for most nitrophenols. Isomeric compounds can be distinguished by the absorption spectra of their respective colored complexes.
For Part I of this series, see ref. 7. 相似文献
Zusammenfassung Ein kolorimetrisches Verfahren zur Bestimmung phenolischer Nitroverbindungen wurde beschrieben. Es beruht auf der gelben Farbreaktion der Nitrophenole mit Imino-bis-propylamin in monochlorbenzolischer Lösung. Carbonyl-und Carboxylgruppen stören nicht. Absorption und Konzentration verhalten sieh bei den meisten Nitrophenolen zwischen 1 und 20g/ml linear. Isomere Verbindungen können an dem Absorptionsspektrum ihrer gefärbten Komplexverbindungen unterschieden werden.
Résumé On décrit une méthode colorimétrique pour le dosage des composés phénoliques contenant la fonction nitro. Elle est fondée sur la formation d'une coloration jaune quand les nitrophénols sont traités par l'imino-bispropylamine en solution dans le monochlorobenzene. Il n'y a pas d'interférence due à la présence de groupes carbonyles et carboxyles dans la molécule. La relation entre la densité optique et la concentration est linéaire dans le domaine de 1 à 20g/ml pour la plupart des nitrophénols. On peut distinguer les composés isomères par les spectres d'absorption de leurs complexes colorés respectifs.
For Part I of this series, see ref. 7. 相似文献
154.
Xuchu Ma Xuebing Li Yi Du Fen Xu Yitai Qian 《Journal of solid state chemistry》2004,177(10):3824-3829
The micro-sized Sb2O3 octahedra can be synthesized on a large scale via a simple PEG-1000 polymer-assisted hydrothermal route (PAHR) in the temperature range of 160-180 °C for 10-14 h. The structures, compositions, and morphologies of the as-synthesized products are derived from X-ray power diffraction pattern, X-ray photoelectron spectra, and field emission scanning electronic microscope. Meanwhile, the optical properties of the micro-sized Sb2O3 octahedra are studied by their photoluminescene spectroscopy and Raman spectrum. Furthermore, the possible growth mechanism of the micro-metered Sb2O3 octahedra is discussed on the basis of a series of supplementary experiments. And it has been found that PEG-1000, sodium tartrate, the reaction temperature, and the reaction time have considerable effects on the final morphology of Sb2O3, while the pH value has an influence on the formation of the Sb2O3 crystals. 相似文献
155.
研究了利用源内碰撞诱导解离(in-source collision—induced dissociation)的高效液相色谱-大气压化学电离质谱(HPLC—APCI/MS)获取人参和西洋参的化学标志物——人参皂甙Rf和拟人参皂甙F11的特征结构信息及鉴别人参和西洋参的方法。在乙腈-水梯度洗脱反相液相色谱及源内碰撞诱导解离条件下,能获得人参皂甙Rf和拟人参皂甙F11的母核离子及去糖基离子的源内碰撞诱导解离谱,从其差别能清楚区分这对同分异构体。本方法对人参皂甙Rf和拟人参皂甙F11的检出限能达到10^-7g柱上样量,简单、快速,单次质谱实验就能鉴别人参和西洋参。 相似文献
156.
Use of synchronous first-derivative fluorimetry for determination of gentamycin is described. Gentamycin reacts with acetylacetone and formaldehyde in pH 5.6 HOAc/NaOAc buffer solution to form N-gentamyl-2,6-dimethyl-3,5-diacethyl-1,4-dihydropyridine[I] which is a fluorescent substance. Spectra of [I] and the reagent blank can be separated with synchronous derivative fluorimetry, and gentamycin can be determined directly. The synchronous spectral peaks of [I] and the reagent blank are at 434 and 411 nm, respectively. The first-derivative peak of [I] is at 425 nm. Effects of pH, foreign ions, buffer system, and heating time on the determination of gentamycin have been examined. The linear regression equation of the calibration graph is C=0.0513H-0.0416, with a correlation coefficient of linear regression of 0.9978. C means total potency of gentamycin: U ml(-1); H means peak height in the linear regression equation calibration graph. The linear range for the determination of gentamycin is from 0.00 to 3.00 U ml(-1). Recovery is from 95.06 to 112.0%, R.S.D. of 3.8%. The results determined by the fluorimetric method agreed roughly with those by the microbiological method. The method is simple and has low detection limit. 相似文献
157.
Mingzhu Liu Rongshi Cheng Jingjia Wu Cheng Ma 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3181-3186
A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO3) (1.08, 5.0 × 10?3, and 0.081 mol/L, respectively). The reaction temperature is ca. 50°C and the reaction time is 2 h. The molecular weight of grafted poly(methylacrylate) has been determined. On the basis of experimental results, the mechanism of grafting has been explored, a new kinetic equation of the graft copolymerization is established: Rp = Kkd [STOH] [Ce4+] + Kkpkd/kt[STOH][M], where K, kd, kp, and kt are constants. The equation fits the results of experiments. © 1993 John Wiley & Sons, Inc. 相似文献
158.
铑-铱分离-向被认为是最困难的课题之一,即使文献曾报道Rh-Ir的分离,但实际Rh并未与萃取剂或吸附剂反应,而是与非贵金属离子一同留在溶液中。我们曾用光谱半定量方法研究了AP树脂对Rh、Ir的吸附行为,结果是Rh不被吸附而Ir能被吸附。本文通过改变Rh的离子状态,使之能被AP树脂吸附完全,而与留在溶液中的非贵金属分离,然后在柱上用不同淋洗液再使Rh-Ir分离。 相似文献
159.
Spin preference and S-T gaps of localized 1,3-diradicals were studied by an orbital phase theory and theoretical calculations. The orbital phase theory was applied to rationalize thermodynamic and kinetic stabilities of diradicals. We theoretically designed some singlet localized 1,3-diradicals, substituted trimethylenes, which are more stable than the lowest triplets. Some diradicals with the four-membered rings, 2,4-disilacyclobutane-1,3-diyls, were designed and shown to have singlet ground states and to be more stable than the sigma-bonded isomers, 2,4-disilabicyclo[1.1.0]butanes. The ab initio calculations supported predictions of the stable carbon-centered localized singlet 1,3-diradicals. 相似文献
160.
A novel lignan: sphaerophyside SC was isolated from ethanolic extract of the seeds of Sphaerophysa salsula (Pall.) DC. The structure of the compound was elucidated mainly on the basis of the 1D NMR and 2D NMR data. 相似文献