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71.
Two new macrocyclic Schiff bases (II) and (III) containing nitrogen ‐ oxygen donor atoms were synthesized by reaction between diethylene triamine or 2,2′‐(ethylenedioxy)bis(ethylamine) and the intermediate compound: 1,4‐bis(6‐methoxy‐2‐formylphenyl)‐1,4‐dioxabutane (I). Identification of these macrocyclic Schiff bases: 1,12, 15,18, 29,32 ‐ hexaaza ‐ [3,4;8,9;20,21;26,27‐tetra‐(6′‐methoxyphenyl)]‐5,8,22,25‐tetraoxa cyclo tetratriacosine‐1,11,18,28‐tetraene. (II) 1,12,21,32‐tetraaza‐[3,4;9,10;23,24;29, 30‐tetra‐(6′‐methoxyphenyl)]‐5,8,15,18,25,28,35,38‐octaoxa cyclo ‐ tetracontane‐1,11,21,31‐tetraene. (III) were determined by elemental analysis (LC‐MS), (IR) and (1H and 13C‐NMR) spectroscopy. The liquid‐liquid extraction of metal picrates such as Ag+ and Cu2+ from aqueous phase to organic phase was carried out using these ligands. The effect of chloroform and dichloromethane as organic solvents over the metal picrate extractions were investigated at 25 ± 0.1 °C by using atomic absorption spectrometer. 相似文献
72.
A new thiahexahelicene bearing a methoxy group, at a selected position on the terminal aromatic ring, was prepared in a good yield through Heck coupling and photocyclization reactions. The X-ray crystal structure of the product indicates that its conformation closely resembles that of the unsubstituted hexahelicene, whose idealized symmetry is C2. Both enantiomers of the new helically chiral hexacyclic system have been successfully separated using (R)-2-phthalimidopropanoic acid chloride as a chiral resolving agent. 相似文献
73.
Djamel Tahtat Mohamed Mahlous Samah Benamer Assia Nacer Khodja Souad Larbi Youcef 《Radiation Physics and Chemistry》2012,81(6):659-665
Chitosan A1, A2 and A3 with molecular weight of 471, 207 and 100 kDa respectively, produced from squid pen chitin was degraded by gamma rays in the solid state and in aqueous solution with various doses in air at ambient temperature. Effect of molecular weight on radiation chemical degradation yield of chain scission and degradation rate constants of γ-irradiated chitosan in solid state and in aqueous solution was investigated. The radiation chemical degradation yield G(s) and degradation rate values were calculated. The molecular weight changes were monitored by capillary viscometry method and the chemical structure changes were followed by UV analysis. The results showed that, the degradation of chitosan was faster in solution, than in solid state. The values of G(s) in solid state and in aqueous solution were respectively 1.1×10?8 mol/J and 0.074×10?7 mol/J for A1, 4.42×10?8 mol/J and 0.28×10?7 mol/J for A2 and 6.08×10?8 mol/J and 0.38×10?7 mol/J for A3. Degradation rate constants values ranged from 0.41×10?5 to 2.1×10?5 kGy?1 in solid state, whereas in solution they ranged from 13×10?5 to 68×10?5 kGy?1. The chitosan A3 was more sensitive to radiolysis than A1 and A2. The chain scission yield, G(s) and degradation rate constants seems to be greatly influenced by the initial molecular weight of the chitosan. Structural changes in irradiated chitosan are revealed by the apparition of absorption peaks at 261 and 295 nm, which could be attributed to the formation of carbonyl groups. In both conditions the peak intensity was higher in chitosan A3 than in A1 and A2, the oxidative products decreased with increasing molecular weight of chitosan. 相似文献
74.
Bassioni G Pillay AE El Kadi M Fegali F Fok SC Stephen S 《European journal of mass spectrometry (Chichester, England)》2010,16(6):679-692
Transition metals can have a significant impact in research related to the dosage optimization of superplasticizers. It is known that the presence of transition metals can influence such doses, and the application of a contemporary instrumental method to obtain the profiles of subsisting transition elements in concrete mixtures would be useful. In this work, inductively-coupled plasma mass spectrometry (ICP-MS) is investigated as a possible tool to track traces of transition metals in concrete mixtures. Depth profiling using ICP-MS on proofed and unproofed concrete shows the presence of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn at trace intensities in the bulk of the samples under investigation. The study demonstrates that the transition metals present in the concrete sample are largely a part of the cement composition and, to a minor degree, a result of exposure to the seawater after curing. The coated concrete samples have a metal distribution pattern similar to the uncoated samples, but slight differences in intensity bear testimony to the very low levels that originate from the exposure to seawater. While X-ray diffraction fails to detect these traces of metals, ICP-MS is successful in detecting ultra-trace intensities to parts per trillion. This method is not only a useful application to track traces of transition metals in concrete, but also provides information to estimate the pore size distribution in a given sample by very simple means. 相似文献
75.
CuCrO2 single crystal, elaborated by the flux method, is a narrow-band-gap semiconductor crystallizing in the delafossite structure
with an indirect optical transition at 2.12 eV. The relatively longer Cu–Cu is consistent with the semi-conducting behavior.
The conductivity in the (001) plans is thermally activated and occurs predominantly by small polaron hopping through mixed-valence
states Cu+/2+ in conformity with a classical dielectric behavior. The activation energy (0.05 eV) gave an effective mass of 9 m
o, indicating that the levels in the vicinity of the Fermi level E
f are strongly localized. The oxide shows an excellent chemical stability over the whole pH range; the semi-logarithmic plot
gave an exchange current density of 0.7 mA cm−2 and a corrosion potential of 0.18 V/SCE in KOH (0.5 M) electrolyte. The electrochemical study is confined in (001) plans, and reversible oxygen intercalation is
evidenced from the cyclic voltammetry. The Mott–Schottky plot (C−2-V) is characteristic of p type conduction and exhibits a linear plot from which a flat band potential of +0.21 V/SCE and a holes density N
A
of 5.06 × 1014 cm−3 were obtained. The photocurrent is due to Cu+: d → d transition and the valence band is positioned at 5.34 eV below vacuum. 相似文献
76.
77.
Souad Dali Herv Lefebvre Rachid El Gharbi Alain Fradet 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):3025-3035
The synthesis of poly(glycolic acid) (PGA) by polyesterification of glycolic acid was studied using ionic liquids, mainly 1,3‐dialkylimidazolium salts, as reaction media. The 1H NMR spectra of PGA oligomers were assigned and end‐group signals were used to follow the reaction. Low PGA yields were obtained by the direct polyesterification of glycolic acid at 200–240 °C, because of monomer evaporation during the reaction. On the other hand, PGAs of DP n up to 45 were obtained by the postpolycondensation of a preformed oligomer in 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIm+Tf2N?). The precipitation of PGA in reaction medium at long reaction times limited the achievable molar mass. Rate constants were determined for catalyzed and noncatalyzed reactions, assuming a second‐order reaction mechanism. The efficiency of esterification catalysts such as Zn(OAc)2 was low in these media, as only about twofold increases in reaction rate were observed. This was assigned to the preferential interaction of Zn2+ with ionic liquid anion instead of the polymer carboxylic acid end‐groups. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3025–3035, 2006 相似文献
78.
Mohsen K.A. Regal Safa S. Shaban Souad A. El-Metwally 《Journal of heterocyclic chemistry》2020,57(3):1368-1378
PTC reaction of coumarin derivative 1 with alkyl halides afforded C4 oxygen alkylation products 2a-d in appreciative yield, whereas with phenyl isothiocyanate gives the C3 addition product 4 ; also, one-pot three-component PTC reaction was investigated. Treatment of coumarin 1 with aromatic aldehydes in different molar ratios gives 3-arylidene derivatives 7a,b and the dicoumarol derivatives 8a,b . Pyrano chromene 9 and pyrano pyridine 10 were obtained by reaction of arylidene 7a with ethyl acetoacetate through Michael cycloaddition reaction. The stability of pyrone ring in 3-arylidene 7 and dicoumarol 8 towards different nucleophilic reagents under reflux and/or fusion conditions has been studied by the action of hydrazine hydrate, ammonium acetate, methyl amine, and p-toluidine afforded compounds 11 and 13a-c . The antimicrobial activity of some synthesized compounds has been investigated. 相似文献
79.
The synthesis and structural characterization of a new hexahelicene derivative is reported. This compound features a new type of structure bearing a bromine atom. Suitable crystals of the latter indicate that its conformation closely resembles that of the unsubstituted [6]helicene, whose idealized symmetry is C2. The optoelectronic properties of this helical hexacyclic system were determined and exhibit a very interesting behavior. 相似文献
80.
Aboul-Fadl T Abdel-Aziz HA Kadi A Ahmad P Elsaman T Attwa MW Darwish IA 《Molecules (Basel, Switzerland)》2011,16(6):5194-5206
A combinatorial library composed of eleven hydrazides A-K and eleven indolin-1,2-dione derivatives 1-11 has been designed to formally generate sublibraries of 22 mixtures, M(1)-M(22) comprising of 121 Schiff bases, A-K(1-11). The designed library has been synthesized by the solution-phase method and microwave-assisted synthetic techniques. The formation of individual compounds of each mixture was confirmed by Direct Analysis in Real Time (DART) as ionization technique connected to an Ion Trap as a mass detector. The synthesized mixtures were evaluated for their antimycobacterial activity against four Mycobacterium strains; M. intercellulari, M. xenopi, M. cheleneoi and M. smegmatis. Variable antimycobacterial activity was revealed with the investigated mixtures and maximum activity was shown by M(8), M(10), M(11), and M(15) with MIC values of 1.5, 3.1, 6.2 and 0.09 μg/mL, respectively. Application of the indexed method of analysis on these active mixtures revealed that compounds D(8), D(10) and D(11) may contribute to the activity of the tested mixtures. 相似文献