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91.
Various alcohols and phenols can be smoothly converted to the corresponding THP ethers using 20 mol % CuSO4·5H2O under mild reaction conditions at room temperature. Some of the major advantages of this procedure are nonaqueous work-up, very good yields, less expensive catalyst and compatibility with other protecting groups. 相似文献
92.
A review with 159 references is presented on the applications of adsorptive stripping voltammetry (AdSV) for determining
trace metal ions in different environmental samples (e.g. water, soil, plant, biological fluids). The analytical applications
of AdSV to biologically active organic compounds (e.g. pharmaceuticals, pesticides, biomolecules) are also discussed.
Received: 18 December 1995/Revised: 8 January 1997/Accepted: 12 January 1997 相似文献
93.
Hassan Sheibani 《Tetrahedron》2004,60(28):5931-5934
2-Pyrone derivatives were prepared in a one step procedure from readily available (chlorocarbonyl)phenyl ketene and 1,3-diketones such as 2,4-pentanedione, 1,3-diphenyl-1,3-propanedione, 1-phenyl-1,3-butanedione, 1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione, 1,3-dimethyl-pyrimidine-2,4,6-trione and ethyl 2,4-dioxopentanoate. A mechanism is presented to account for the formation of the products. This method provides an easy route to prepare 3,4,5,6-tetrasubstituted 2-pyrones in good to excellent yields and in a short experimental time. 相似文献
94.
M. S. K. Youssef Kh. M. Hassan F. M. Atta M. S. Abbady 《Journal of heterocyclic chemistry》1984,21(5):1565-1568
3-Hydrazino-7-methyl-5-phenyl-5H-pyrazolo[3,4-c]-as-triazine 1 underwent ring closure and/or condensation reaction with formic acid, acetic acid, acetic anhydride and benzoyl chloride to afford 1H-pyrazolo-[3,4-d]-s-triazolo[3,4-c]-as-triazines 2, 5 and 7a and/or N-acyl derivatives 3, 4 and 6 . N-Acyl derivatives 3 and 6 underwent cyclisation reaction on treatment with phosphoryl chloride to give 5 and 7a . 3-Methyl-1-phenyl-8-aryl-1H-pyrazolo[3,4-e]-s-triazolo[34,-c]-as-triazines 7 were also prepared by the reaction of the hydrazono derivatives 8 wit thionyl chloride. On treatment of 1 with nitrous acid gave the 8H-pyrazolo[3,4-e]tetrazolo-[5,1-c]-as-triazine 9 . Compound 1 underwent ring closure with carbon disulphide or ethyl chloroformate to 1,7-dihydro-8H-pyrazolo[3,4-e]-s-triazolo[3,4-c]-as-triazine derivatives 10 and 12 . Reaction of 1 with ethyl acetoacetate or acetylacetone gave 3-pyrazolo derivatives 13 and 14 . 相似文献
95.
A simple, rapid and sensitive spectrophotometric method is described for the quantitative determination ofN-substituted phenothiazines. The method depends on the formation of a stable phenothiazine free radical cation by the use ofN-bromophthalimide as oxidising agent in a strong acid medium (methanol/ sulphuric acid 1 1 v/v). The produced red or violet color possesses absorption maximum range from 500 to 530 nm. A linear relationship exists between the absorbance at (max) and concentration in the range 5 to 40 g ml–1 with apparent molar absorptivities range from 6 × 103 to 12 × 1031 mol–1 cm–1. The color is developed instantaneously for all the studied phenothiazines except for thioproperazine mesylate, trifluoperazine dihydrochloride and prochlorperazine mesylate that require 25, 15 and 25 min, respectively, for complete reaction. The developed colors are stable over 24 h. The average % recovery is 99.85±0.61 to 100.28±0.95. The method was applied successfully to the microdetermination of chlorpromazine HCl, promethazine HCl, pericyazine, thioproperazine mesylate, perphenazine, prochlorperazine mesylate, trimeprazine tartrate and trifluoperazine 2HCl either in pure form or incorporated in their pharmaceutical preparations. The results of analysis are in good agreement with those of the official B.P. 1988 and USP XXII. 相似文献
96.
M. Amin H. H. Hassan E. M. Abdel-Bary 《Journal of polymer science. Part A, Polymer chemistry》1974,12(11):2651-2657
Styrene–butadiene rubber (SBR) charged with 50 phr of HAF carbon black has been found to show a positive temperature coefficient of resistivity close to 0.07/°C at 27°C. Beyond a point (75°C) of minimum conductivity, however, it behaves as a normal noncrystalline semiconductor with a resistivity which decreases with rise of temperature with an activation energy of 0.56 eV. Blending the composition with poly(vinyl chloride) (PVC) shifts the minimum towards lower temperatures. The descending branch of the conductivity versus reciprocal absolute temperature characteristic is probably associated with thermal expansion of tunnelling paths separating the conducting carbon particles. 相似文献
97.
Refat M. Hassan 《Journal of polymer science. Part A, Polymer chemistry》1993,31(5):1147-1151
The kinetics of decomposition of [Alg · Mn VIO42?] intermediate complex have been investigated spectrophotometrically at a constant ionic strength of 0.5 mol dm?3. The decomposition reaction was found to be first-order in the intermediate concentration. The results showed that the rate of reaction was base-catalyzed. The kinetic parameters have been evaluated and found to be ΔS? = ?103.88±6.18 J mol?1 K?1, ΔH? = 51.61 ± 1.02 kJ mol?1, and ΔG? = 82.57 ± 2.86 kJ mol?1, respectively. A reaction mechanism consistent with the results is discussed. © 1993 John Wiley & Sons, Inc. 相似文献
98.
Kristian Lappalainen Katariina Yliheikkil Adnan S. Abu‐Surrah Mika Polamo Markku Leskel Timo Repo 《无机化学与普通化学杂志》2005,631(4):763-768
Iron(II) and cobalt(II) complexes ( 7 ‐ 15 ) based on new aldimine 2, 6‐bis[(imino)methyl]pyridine ( 1 , 2 , 4 , 6 ) and ketimine (2, 6‐bis[(imino)ethyl]pyridine ( 3 , 5 ) ligands with bulky chiral aliphatic or aromatic terminal groups have been prepared and characterized by 1H NMR, 13C NMR, IR‐, mass spectroscopy (EI), and elemental analysis. The complex [CoCl2(BBoMP)]·1/2 CHCl3 ( 13 ) (BBoMP: 2, 6‐bis{(R‐(+)‐(bornylimino)‐methyl}pyridine) crystallizes in monoclinic space group P21 with cell dimensions: a = 7.6603(11) Å, b = 28.3153(14) Å, c = 13.537(2) Å, V = 2908.1(6) Å3, Z = 4. The coordination sphere around Co is distorted trigonal bipyramidal. 相似文献
99.
H. A. Azab A. M. El-Nady A. Hassan R. S. A. Azkal 《Monatshefte für Chemie / Chemical Monthly》1994,125(10):1059-1066
Summary Potentiometric equilibrium measurements have been made for the interaction of adenosine-5-mono-,-di-, and -triphosphate, and Co(II) with biologically important secondary ligands (malic, maleic, succinic, tartaric, citric, and oxalic acid). The formation of various 1:1:1 mixed ligand complexes inferred from the potentiometric titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP and the secondary ligand acids have been refined with a computer program. In some systems, the ternary complexes are found to be more stable than the corresponding binary ones. In some ternary systems studied, interligand interactions or some cooperativity between the coordinate ligands, possibly H bond formation, have been found to be most effective in deciding the stability of the complexes formed in solution. Stabilities of mixed ligand complexes increase in the orderAMP <ADP <ATP. With respect to the secondary ligands, the formation constants of the mixed ligand complexes decrease in the following order: succinic > maleic > tartaric > malic > citric > oxalic acid.
Potentiometrische Untersuchung der Bildungsgleichgewichte von binären und ternären Komplexen von Kobalt(II) mit Adenosin-5-mono-, -di- und -triphosphat und einigen biologisch bedeutenden polybasischen Sauerstoffsäuren
Zusammenfassung Die Wechselwirkung vonAMP,ADP undATP mit Co(II) und einigen biologisch interessanten Sekundärliganden (Bernsteinsäure, Hydroxybernsteinsäure, Maleinsäure, Weinsäure, Zitronensäure und Oxalsäure) wurde bei 25°C und einer lonenstärke von 0.1M KNO3 potentiometrisch untersucht. Die Titrationskurven zeigen das Vorliegen von Species der Zusammensetzung 1:1:1 an. Die geschätzten Bildungskonstanten der Komplexe und die Dissoziationskonstanten der Liganden wurden mittels eines Computerprogramms optimiert. In einigen der untersuchten Systeme sind die ternären Komplexe stabiler als die sekundären. Die Stabilität der Verbindungen hängt im wesentlichen von Interligandwechselwirkungen — möglicherweise der Ausbildung von Wasserstoffbrückenbindungen — ab. Die Stabilität der Komplexe mit gemischten Liganden steigt in der ReihenfolgeAMP <ADP <ATP und fällt entsprechend der Serie Bernsteinsäure > Maleinsäure > Weinsäure > Hydroxybernsteinsäure > Zitronensäure > Oxalsäure.相似文献
100.
Ali Z. Abu Zuhri 《Monatshefte für Chemie / Chemical Monthly》1987,118(6-7):749-757
The polarographic behaviour of 1,3-bis[(2-pyridyl)methyleneamino]thiourea (PMAT) in solutions of varyingpH has been studied both in the absence and presence of Triton X-100 (T.X-100). The mechanism for the reduction process is discussed. The adsorption effect of electrochemically inactive T.X-100 on the polarographic waves ofPMAT has been investigated. The values of the kinetic parameters for the electrode reaction at differentpH values have been computed. The applicability of the polarographic method for determination ofPMAT is also discussed.
Das polarographische Verhalten von 1,3-Bis[(2-pyridyl)methylenamino]-thioharnstoff (PMAT) in Anwesenheit und Abwesenheit von Triton X-100. Die polarographische Bestimmung vonPMAT
Zusammenfassung Es wurde das polarographische Verhalten vonPMAT in Lösungen mit verschiedenempH sowohl in Gegenwart als auch ohne Triton X-100 (T.X-100) untersucht. Es wird ein Mechanismus für den Reduktionsprozeß diskutiert. Der Adsorptionseffekt des elektrochemisch inaktiven T.X-100 wurde hinsichtlich der polarographischen Wellen vonPMAT untersucht. Die kinetischen Parameter der Elektrodenreaktion wurden für verschiedenepH-Werte ermittelt. Ebenso wird die Anwendbarkeit der polarographischen Methode für die Bestimmung vonPMAT diskutiert.相似文献