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51.
A technique for determination of enantiomeric excess of cathinone, 2-amino-1-phenyl-1-propanone, by use of the chiral lanthanide shift reagent (LSR), tris[3-(heptafluoropropylhydroxymethylene)-d-camphorato]europium (III), Eu (HFC)3, is described. The hydrochloride salt of the cathinone sample is first converted directly to the N-acetyl derivative without need for isolation of the potentially unstable cathinone free base. Addition of Eu (HFC)3 to the crude acetylated cathinone resulted in near-baseline resolution of the CH 3CO resonances of the enantiomers. Analytical utility and the sense of magnetic nonequivalence of this signal were demonstrated using “spiked” non-racemic samples. 相似文献
52.
H/D Isotope effects in fluorination of aromatic compounds with NF type reagents have been studied to reveal the reaction mechanism. The results obtained are consistent with a polar SEAr mechanism. Small deuterium isotope effects (kH/kD = 0.86-0.99) show that decomposition of a Wheland-type intermediate is not rate determining. The first example of a 1,2-hydrogen shift accompanying electrophilic fluorination of arenes has been observed in the fluorination of 1,3,5-trideuterobenzene. 相似文献
53.
Severino C.B. Oliveira Elaine C.S. Coelho Thiago M.G. Selva Francyana P. Santos Mrio C.U. Araújo Fabiane C. Abreu Valberes B. Nascimento 《Microchemical Journal》2006,82(2):220-225
A universal and easily ON–OFF time operated coulometric flow cell for generation of chemicals is proposed. The cell can be used for generation of reagents, titrants or standard solutions, and can be coupled to analytical equipments in combination with flow systems for generation of micro-quantity amounts of chemicals in a wide concentration range. Platinum wire electrodes and other common laboratory available materials were employed in the cell assembly. The application of the cell for analytical purposes was illustrated by employing it for generating triiodide ions as a carrier in a flow injection analysis system applied to the analysis of dipyrone in pharmaceuticals, and as a titrant in a flow-batch analysis system applied for analysis of ascorbic acid in natural orange juice samples. Preliminary studies demonstrate that such a flow cell is suitable to allow the use of unstable reagents in analytical chemistry, since they can be generated in a closed system and promptly used in subsequent reactions. In addition, it offers advantages of saving chemicals, time and specially the laborious calibrating standard solutions preparation task of routine laboratories. Taking in account its analytical performance, the proposed cell promises to be an important tool in analytical chemistry with a great competition potential as compared to the other ones proposed in the literature. 相似文献
54.
11NTRODUCTIoNThederivativesofdiazaphospholidinoneorthecorrespondingthionesareknowntopossessinterestingbiologicalproperties,suchasherbicidalactivity"'2i.Inrecentyears,itwasreportedthatthel,4,2-diazaphospholindine-5-thione-2havegoodselectiveherbicidalactivity"'41.Tolookformoreeffectiveherbicideswithlowtoxicity,aseriesofnovel1-(o-methylphenyl)-2-(p-methoxyphenyl)-phospholidin-4-thione-sulfideshavebeensynthesizedandtheirmolecularstructuresstudied.PreliminarybioassaysshowthatthesecomPoundshaveg… 相似文献
55.
The synthesis of three bipyridyl-tagged reagents and one scavenger is described. Of the three reagents, the carbodiimide derivative proved to be effective as a coupling reagent for amide formation and the removal of the coupling side product from the reaction mixture by complexation onto a Cu-derivatised resin has been successfully demonstrated. This purification process was thoroughly optimised using a DOE approach and the procedure subsequently applied to the use of a bipyridyl-tagged amine as an isocyanate scavenger. Preliminary results clearly demonstrate the potential of using chelation tags such as bipyridine units as a means for removing solution phase reagents and scavengers from reaction mixtures providing an attractive alternative to their resin-bound and fluorous-tagged counter-parts. 相似文献
56.
Jayanta Dey Nayan Banerjee Swikriti Daw Prof. Joyram Guin 《Angewandte Chemie (International ed. in English)》2023,62(44):e202312384
Utilization of oxime ethers as bifunctional reagents remains unknown. Herein, we present a mechanistically distinct strategy that enables oximesulfonylation of olefins using sulfonyl-oxime-ethers as bifunctional reagents under metal-free photochemical conditions. Via concomitant C−S and C−C bond formation, the process permits incorporation of oxime and sulfonyl groups into olefins in a complete atom-economic fashion, providing rapid access to multi-functionalized β-sulfonyl oxime ethers with good yields and stereoselectivity. The method is amenable to functionalization of complex bioactive molecules and is shown to be scalable. A radical chain mechanism initiated via photochemical Hydrogen Atom Transfer (HAT) mediated N−O bond cleavage is suggested for the process, based on our results on mechanistic investigations. 相似文献
57.
58.
An Jingru Lin Jinming 《高等学校化学研究》1991,7(1):32-36
The electrochemiluminescence (ECL) of a new reagent 6- (2-hydroxy- 4 diethy laminophenylazo)-2,3-dihydro-1 ,4-phthalazine-1,4-dione (HDEA) in a basic aqueous so lution was studied by using the apparatus designed by ourselves. Trace amounts of silver ( Ⅰ ) shows a significant effect on the efficiency of light emission of HDEA during a positive trigonometrical wave pulse was exerted on the solution. The linear relationship between the light intensity and the concentration of silver( Ⅰ ) occurs in the range of 5. 0×10-8 to 3. 0×10-8 mol/L Ag(Ⅰ ) in a medium of KOH-KCl-HDEA (pH= 12. 8). The detection limit of the method is 2. 0×10-8 mol/LAg( Ⅰ ), and the r. s. d. for 1.0×10-7 mo)/L Ag ( Ⅰ ) is 5%. Of 21 metal ions concerned, only nickel( Ⅱ ), cerium( Ⅳ ) and cobalt( Ⅱ ) interfere the silver detection seriously; Ⅰ and Br also have some interference. 相似文献
59.
一种新的褪色光度法测定Cr^3+的方法研究 总被引:5,自引:0,他引:5
提出了一种褪色光度法测定Cr~(3+)的新方法。新的叠氮试剂3-(苯偶氮苯)-1-三氮烯苯甲酸钠(PTBAS)在NaOH-Na_2B_4O_7缓冲液中,在表面活性剂OP的存在下,与Cd~(2+)反应后形成一种橙红色的络合物。测定Cd~(2+)时,当有微量Cr~(3+)共存时,络合物吸光度值明显降低,利用这种现象可以间接测定Cr~(3+)。测得Cr~(3+)的表观摩尔吸光系数ε=1.12×10~5,线性范围为0~0.4μg·ml~(-1)。方法选择性很高,很多常见离子不干扰测定,可直接用于水样中Cr~(3+)的测定。 相似文献
60.
For point‐of‐care examination, total CK (creatine kinase: adenosine‐5‐triphosphate‐creatine phosphotransferase, EC 2.7.3.2) biosensors were developed and optimized. The biosensors were fabricated with three‐Au‐electrode system modified with polyvinylpyridine‐osmium‐wired horseradish peroxidase (PVP‐Os‐HRP) redox polymer film. The reagents were separately immobilized on the single layer biosensor and double layer biosensor which contained lens paper layer and the surface layer of the working electrode. The mediator, the working potential, the structure of working electrode and the stabilizer agent were studied. The biosensor with double reagent layer showed good stability at room temperature (≥2 months) and the biosensor with single reagent layer had excellent response signal (a sensitivity of 11 nA L U?1 cm?2). 相似文献