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81.
Summary The reactions of aldehydic and ketonic Schiff bases derived from hydrazine-S-methyl dithiocarboxylate and thiosemicar-bazide with cobalt(II) acetate were investigated. Octahedral tris ligand cobalt(III) chelates were formed with aldehydic Schiff bases whereas tetrahedral bis ligand cobalt (II) chelates were isolated with ketonic Schiff bases.N-isopropylidene hydrazine-S-methyldithiocarboxylate, however, gave both octahedral tris cobalt(III) and tetrahedral bis cobalt(II) chelates. These results are interpreted in terms of the steric requirements of the Schiff base used. 相似文献
82.
M. N. Cheema M. Mufazzal Saeed Akbar Ali Munir Ahmed 《Journal of Radioanalytical and Nuclear Chemistry》1994,178(1):153-163
Extraction of Hg(II), Se(IV), Mn(II) and Co(II) has been carried out with 1-phenyl-3-methyl-4-trifluoroacetyl-2-pyrazolin-5-one (HPMTFP) and triphenylphosphine oxide (TPPO) into chloroform from pH 1–10. Quantitative extraction of Hg(II), Mn(II) and Co(II) at pH 4 with equimolar 0.05M (PMTFP+TPPO) in chloroform was observed. Se(IV) remains unextracted at this pH range. The stoichiometric composition of the extracted complexes M(PMTFP)2·nH2O (M=Mn, Hg), M(PMTFP)2·2TPPO (M=Mn and Co) and Co(PMTFP)2·TPPO·H2O at less than 0.1M TPPO has been established. The formation constantsK
m,0 andK
m,n and stability constants
m,n have been computed. The analytical method developed was applied to the IAEA standard reference material (SRM) potato fluor V-4 for the determination of these elements using NAA technique. 相似文献
83.
Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide
A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly‐5, 2′: 5′, 2″‐terthiophine‐3‐carboxylic acid), poly‐TTCA through the formation of amide bond between carboxylic acid groups of poly‐TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly‐TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X‐ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly‐TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73 s?1. The biosensor efficiently detected xanthine through oxidation at +0.35 V and reduction at ?0.25 V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10?6?1.0×10?4 M and 5.0×10?7 to 1.0×10?4 M, respectively. The detection limits were determined to be of 1.0×10?6 M and 9.0×10?8 M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. 相似文献
84.
Ramadan Ahmed Mekheimer Kamal Usef Sadek Hisham Ahmed Abd El‐Nabi Afaf Abd El‐Hameid Mohamed Ehab Anwer Ebraheem Michael B. Smith 《Journal of heterocyclic chemistry》2005,42(4):567-574
Ethyl 3‐amino‐4‐chlorothieno[3,2‐c]quinoline‐2‐carboxylate ( 4 ) is a versatile synthon, prepared by reacting an equimolar amount of 2,4‐dichloroquinoline‐3‐carbonitrile ( 1 ) with ethyl mercaptoacetate ( 2 ). Ethyl 5‐alkyl‐5H‐1‐thia‐3,5,6‐triazaaceanfhrylene‐2‐carboxylates 9a‐c , novel perianellated tetracyclic heteroaro‐matics, were prepared by refluxing 4 with excess of primary amines 7a‐c to yield the corresponding amino‐thieno[3,2‐c]quinolines 8a‐c . Subsequent reaction with an excess of triethyl orthoformate (TEO) furnished 9a‐c . Reaction of 4 with TEO in Ac2O at reflux, gave the simple acetylated compounds, thieno[3,2‐c]‐quinolines 12 and 13 . Refluxing 4 with benzylamine ( 7d ) gave 10 , and subsequent treatment with TEO gave the tetracyclic compound 11 . Refluxing 13 with an excess of alkylamines 7a‐d gave the fhieno[3,2‐c]quino‐lines 15 . Refluxing the aminothienoquinolines 8b with an excess of triethyl orthoacetate gave thieno[3,2‐c]quinoline 17 , while heating with Ac2O gave 18 and 19 , with small amounts of 16 . Reaction of 8a,b with ethyl chloroformate and phenylisothiocyanate generated the new 1‐thia‐3,5,6‐triazaaceanthrylenes 20a,b and 21a,b , respectively. Diazotization of 8a‐c afforded the novel tetracyclic ethyl 5‐alkyl‐5H‐1‐fhia‐3,4,5,6‐tetraazaaceanthrylene‐2‐carboxylates 22a‐c in good yields. 相似文献
85.
Highly sensitive catalytic determination of molybdenum 总被引:1,自引:0,他引:1
A novel, highly sensitive, selective, and simple kinetic method was developed for the determination of Mo(VI) based on its catalytic effect on the oxidation of 1-amino-2-naphthol-4-sulfonic acid (ANSA) with H2O2. The reaction was followed spectrophotometrically by tracing the oxidized product at 465 nm after 30 min of mixing the reagents. The optimum reaction conditions were: 10 mmol l−1 ANSA, 50 mmol l−1 H2O2, 100 mmol l−1 acetate buffer of pH 5.0 ± 0.05 and at 40 °C. Addition of 200 μg ml−1 diethylenetriaminepentaacetic acid (DTPA) conferred high selectivity for the proposed method. Following the recommended procedure, Mo(VI) could be determined with a linear calibration graph up to 2.5 ng ml−1 and a detection limit, based on the 3Sb-criterion, of 0.027 ng ml−1. The unique sensitivity and selectivity of the implemented method allowed its direct application to the determination of Mo(VI) in natural and industrial waste water. The method was validated by comparison with the standard ETAAS method. Moreover, published catalytic-spectrophotometric methods for the determination of molybdenum were reviewed. 相似文献
86.
Kamel Guedri Tahmoor Bashir A. Abbasi Waseh Farooq Sami Ullah Khan M. Ijaz Khan Mohammed Jameel Ahmed M. Galal 《印度化学会志》2022,99(9):100614
The electroosmotic peristaltic flow of modified hybrid nanofluid in presence of entropy generation has been presented in this thermal model. The Hall impact and thermal radiation with help of nonlinear relations has also been used to modify the analysis. The assumed flow is considered due to a non-uniform trapped channel. The properties of modified hybrid nanofluid model are focused with interaction of three distinct types of nanoparticles namely copper (, silver () and aluminum oxide ( The mathematical modeling and significances of entropy generation and Bejan number are identified. With certain flow assumptions, the governing equations are attained for optimized peristaltic electroosmotic problem. Widely used assumptions of long wave length and low Reynolds number reduced the governing equations in ordinary differential equations. The ND solver is flowed for the solution process. The physical significant of results is observed by assigning the numerical values to parameters. 相似文献
87.
Ahmed R. Hassan Khadiga F. Amer Sayed A. El-Toumy John Nielsen 《Natural product research》2019,33(8):1135-1139
Isolation of flavonoids from the aerial parts of Taverniera aegyptiaca Bioss. (Fabaceae) led to identification of one new flavonol glycoside, isorhamnetin-3-O-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranoside (1), along with eleven compounds, which previously have not been isolated from this plant quercetin-3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside] (2), isorhamnetin-3-O-α-l-arabinopyranoside (3), quercetin-3-O-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside (4), isorhamnetin-3-O-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside (7), isorhamnetin 3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside] (8), isorhamnetin 3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside] (9), kaempferol 3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside] (10), isorhamnetin (11), 4,4′-dihydroxy-2′-methoxychalcone (12), formononetin (13) and calycosin (15)] and some compounds already known from this plant [quercetin-3-O-robinobioside (5), isorhamnetin-3-O-robinobioside (6), afrormosin (14) and odoratin (16)]. 相似文献
88.
Abdel-Magid AF Carson KG Harris BD Maryanoff CA Shah RD 《The Journal of organic chemistry》1996,61(11):3849-3862
Sodium triacetoxyborohydride is presented as a general reducing agent for the reductive amination of aldehydes and ketones. Procedures for using this mild and selective reagent have been developed for a wide variety of substrates. The scope of the reaction includes aliphatic acyclic and cyclic ketones, aliphatic and aromatic aldehydes, and primary and secondary amines including a variety of weakly basic and nonbasic amines. Limitations include reactions with aromatic and unsaturated ketones and some sterically hindered ketones and amines. 1,2-Dichloroethane (DCE) is the preferred reaction solvent, but reactions can also be carried out in tetrahydrofuran (THF) and occasionally in acetonitrile. Acetic acid may be used as catalyst with ketone reactions, but it is generally not needed with aldehydes. The procedure is carried out effectively in the presence of acid sensitive functional groups such as acetals and ketals; it can also be carried out in the presence of reducible functional groups such as C-C multiple bonds and cyano and nitro groups. Reactions are generally faster in DCE than in THF, and in both solvents, reactions are faster in the presence of AcOH. In comparison with other reductive amination procedures such as NaBH(3)CN/MeOH, borane-pyridine, and catalytic hydrogenation, NaBH(OAc)(3) gave consistently higher yields and fewer side products. In the reductive amination of some aldehydes with primary amines where dialkylation is a problem we adopted a stepwise procedure involving imine formation in MeOH followed by reduction with NaBH(4). 相似文献
89.
Two-dimensional capillary electrophoresis was used for the separation of proteins and biogenic amines from the mouse AtT-20 cell line. The first-dimension capillary contained a TRIS–CHES–SDS–dextran buffer to perform capillary sieving electrophoresis, which is based on molecular weight of proteins. The second-dimension capillary contained a TRIS–CHES–SDS buffer for micellar electrokinetic capillary chromatography. After a 61-s preliminary separation, fractions from the first-dimension capillary were successively transferred to the second-dimension capillary, where they further separated by MECC. The two-dimensional separation required 60 min. 相似文献
90.
Mamdouh Ahmed Mohamed Taha 《中国化学会会志》2005,52(1):137-140
Reaction of 6‐mercapto‐7H‐1,2,4‐triazolo[1,5‐d]tetrazole ( 1 ) wtih 1,2‐phenylenediamine afforded N‐{7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,2‐phenylenediamine which was cyclized to benzimidazolyl‐1,2,4‐triazolo[1,5‐d]tetrazoles using various one‐carbon cyclizing agents. Also, the treatment of 1 with maleic anhydride or phthalic anhydride gave the corresponding thio derivatives followed by hydrazinolysis to afford the thio heterobicyclic systems. Former structures of the products have been established upon elemental and spectral analyses. 相似文献