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841.
1-(偶氮苯基)-3-(3,5-二溴-2-吡啶)-三氮烯的合成及其与镉的显色反应 总被引:10,自引:0,他引:10
报道了 1 (偶氮苯基 ) 3 ( 3,5 二溴 2 吡啶 ) 三氮烯的合成及其与镉的显色反应。在TritonX 1 0 0存在下 ,于pH 1 0 .9的Na2 B4O7 NaOH缓冲介质中 ,镉与ABDBPDT形成摩尔比 1∶3型红色配合物。试剂及配合物的最大吸收波长分别为 430nm和 5 30nm。表观摩尔吸光系数为 1 .75× 1 0 5L·mol- 1 ·cm- 1 。镉含量在 0 μg/2 5mL~ 1 2 μg/2 5mL范围内符合比耳定律 相似文献
842.
Kedong Xia Junpo Guo Cuijuan Xuan Ting Huang Zhiping Deng Lingxuan Chen Deli Wang 《中国化学快报》2019,30(1):192-196
Nitrogen doped carbon nanosheets supported molybdenum carbides nanoparticles (MoxC/NCS) have been synthesized by tuning the mass ratio of melamine and ammonia molybdate. The Mo2C/NCS-10 exhibits superior electrocatalytic performance and stability for HER, which was attributed to N-doped carbon nanosheets, small particle size, mesoporous structure, and large electrochemical active surface area. 相似文献
843.
Kazuo Mukai Kanae Nagai Aya Ouchi Tomomi Suzuki Katsuhiro Izumisawa Shin-Ichi Nagaoka 《国际化学动力学杂志》2019,51(9):643-656
Measurements of aroxyl radical (ArO•)-scavenging rate constants () of antioxidants (AOHs) (α-tocopherol (α-TocH) and three catechins (CatHs) (ie, epicatechin (EC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG)) were performed in ethanol solution, using stopped-flow spectrophotometry. values were measured not only for each AOH, but also for the mixtures of two AOHs (α-TocH and CatH). A notable synergistic effect that the value of α-TocH increases 1.29, 1.84, and 1.65 times under the coexistence of constant concentrations of EC, EGC, and EGCG, respectively, was observed for the solutions including α-TocH and CatH. Similarly, values of CatHs (EC, EGC, and EGCG) increased 1.72, 2.25, and 2.34 times under the coexistence of constant concentrations of α-TocH, respectively. UV-Vis absorption of α-tocopheroxyl radical (α-Toc•) (λmax = 428 nm), which had been produced by reaction of α-TocH with ArO•, decreased remarkably under the coexistence of α-TocH and CatHs due to the fast α-TocH-regeneration reaction by CatHs. The result suggests that the prooxidant reaction due to α-Toc• is suppressed by the coexistence of CatHs. By analyzing the formation and decay curves of α-Toc•, it has been ascertained that one molecule of EGCG having three OH groups at B-ring may rapidly regenerate three molecules of α-Toc• to α-TocH. 相似文献
844.
845.
Ketones react with an array of aldehydes in dioxane at 80 °C in the presence of a catalytic amount of RuCl2(PPh3)3 along with KOH to give the corresponding α-alkylated ketones in moderate to good yields. A reaction pathway involving base-catalyzed cross-aldol reaction between ketones and aldehydes to form α,β-unsaturated ketones and regioselective reduction of carbon-carbon double bond of α,β-unsaturated ketones is proposed for this catalytic process. 相似文献
846.
Din-Goa Liu Jyh-Fu Lee Mau-Tsu Tang 《Journal of molecular catalysis. A, Chemical》2005,240(1-2):197-206
X-ray absorption spectroscopy (XAS) was employed to characterize carbon black supported Pt-Ru catalysts, which are commercially available to be utilized as the anode of polymeric-electrolyte-membrane fuel cells. Both Pt and Ru were found partially oxidized in the as-received form. Upon exposure to hydrogen at room temperature, the catalysts were completely reduced to the metallic state. The bimetallic nanoparticles on the Pt-Ru/C catalysts possess an inner core enriched in Pt, which is surrounded by a Ru-rich outer shell. Such a core–shell structure retained even at an elevated reduction temperature of 623 K. Temperature-programmed surface reaction (TPSR) was carried out to explore the reactivity of adsorbed CO toward hydrogen on various catalysts. Both the peak temperature of the TPSR profile and the amount of methane generated during the course of TPSR were sensitive to the surface composition of Pt–Ru nanoparticles. In combination of XAS and TPSR results, a slight difference in the nanostructure between two Pt-Ru/C catalysts was manifested. 相似文献
847.
Assessing the non-specific hydroxyl radical scavenging properties of melanoidins in a Fenton-type reaction system 总被引:1,自引:0,他引:1
Francisco J. Morales 《Analytica chimica acta》2005,534(1):171-176
Soluble high molecular weight fraction (>10 kDa, named melanoidins) was isolated from Maillard reaction model systems, coffee, beer and sweet wine by ultrafiltration. Deoxyribose method was adjusted for measuring the hydroxyl radical scavenging properties of melanoidins. The presence of competitive melanoidins with deoxyribose for OH decrease the rate of deoxyribose degradation. Possible interferences to the deoxyribose method have been evaluated. Most of isolated melanoidins exhibited a variable and measurable non-site-specific hydroxyl scavenging activity in a Fenton-type reaction system. The iron reducing properties of melanoidins at the reaction conditions were evaluated with ferrozine. It has established a kinetic approach to assess the second rate constants of hydroxyl radical scavenging reactions of melanoidins. This approach may be a valuable tool for addressing the structure-activity relationships of melanoidins in a future. There is no correlation between browning (absorbance at 420 nm) and efficiency for scavenging hydroxyl radicals in solution. 相似文献
848.
Mecheril V. Nandakumar 《Tetrahedron》2005,61(41):9775-9782
A Pd2dba3/P(i-BuNCH2CH2)3N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners. 相似文献
849.
A convenient one-pot synthesis of α-fluoro-α,β-unsaturated esters from ethoxy- and tert-butoxycarbonylmethyltriphenylphosphonium bromide was developed. The fluorinated phosphoranes, generated in situ from alkoxycarbonylmethyltriphenylphosphonium bromides and 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor®), undergo a Wittig reaction with aldehydes to yield α-fluoro-α,β-unsaturated esters with (Z)-selectivity. 相似文献
850.
Shuji YasuikeSatoru Okajima Kentaro YamaguchiHiroko Seki Jyoji Kurita 《Tetrahedron》2003,59(27):4959-4966
Racemic 2,2′-bis[diarylstibano]-1,1′-binaphthyls [(±)-BINASbs] and 2,2′-bis[di(p-tolyl)bismuthano]-1,1′-binaphthyl [(±)-BINABi], which are the antimony and bismuth congeners of BINAP, have been prepared from 2,2′-dibromo-1,1′-binaphthyl (DBBN) via 2,2′-dilithio-1,1′-binaphthyl intermediate by treatment with the appropriate metal halides [(p-Tol)2SbBr, Ph2SbBr and (p-Tol)2BiCl]. The optical resolution of the (±)-BINASbs could be achieved via the separation of a mixture of the diastereomeric Pd-complexes derived from the reaction of (±)-BINASbs with di-μ-chlorobis{(S)-2-[1-(dimethylamino)-ethyl]phenyl-C1,N}dipalladium(II). Optically active (R)-BINASb and (R)-BINABi could be also obtained from optically active (R)-DBBN by the same procedure. The enantiopure BINASbs have been shown to be effective chiral ligands for the rhodium-catalyzed asymmetric hydrosilylation of ketones. 相似文献