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891.
E. M. Afsah M. M. Abou-Elzahab M. T. Zimaity G. R. Proctor 《Monatshefte für Chemie / Chemical Monthly》1984,115(8-9):1065-1070
When -keto-ester1 a was reacted with dimethyl acetylenedicarboxylate ring expansion occurred to give substituted cyclooctadienones.Michael reactions of the title compounds1 with unsaturated ketones gave adducts, some of which underwent further cyclization reactions. A new route to -tetralone ring system10 via cyclization of the intermediateMichael adduct9 is described.
Michael- und Ringerweiterungsreaktionen von 6-Carboethoxy-3,5-diaryl-2-cyclohexen-1-onen
Zusammenfassung Bei der Reaktion von -Keto-ester1 a mit Dimethyl-acetylendicarboxylat wurden unter Ringerweiterung substituierte Cyclooctadienone erhalten. DieMichael-Reaktion der Titelverbindung1 mit ungesättigten Ketonen ergab Addukte, von denen einige weitere Cyclisierungsreaktionen eingingen. Es wird ein neuer Weg zum -Tetralonsystem10 über die Cyclisierung des intermediärenMichael-Addukts9 beschrieben.相似文献
892.
Mohammad R.?SaidiEmail author Mohammad?Nazari 《Monatshefte für Chemie / Chemical Monthly》2004,135(3):309-312
Summary. The solid LiClO4-mediated one-pot reaction of aldehydes with secondary amines and C nucleophiles afforded the corresponding aminoalkylation products in high yields. Unlike the previous reported procedure, the aminoalkylation of aldehyde was achieved in the presence of only 0.5 equivalents of solid lithium perchlorate in dichloromethane as the solvent with good to high yields at room temperature. 相似文献
893.
Bredikhina Z. A. Pashagin A. V. Savel"ev D. V. Bredikhin A. A. 《Russian Chemical Bulletin》2001,50(3):436-439
Nonracemic -blockers, viz., (S)-propranolol and (S)-timolol, were prepared from (S)-glycidol in three steps consisting in the reaction with SOCl2 followed by the reaction of the resulting (4S)-4-chloromethyl-2-oxo-1,3,2-dioxathiolanes with the corresponding phenol and the final cleavage of (4R)-aryloxymethyl sulfites under the action of amines in DMF. 相似文献
894.
Maria do Carmo B. Pimentel Eduardo Henrique M. Melo José Luiz Lima Filho William M. Ledingham Nelson Durán 《Applied biochemistry and biotechnology》1997,66(2):185-195
This work is a study of lipase production by a Brazilian strain ofPenicillium citrinum using an inexpensive and simple medium without organic nitrogen sources and of some important industrial properties, including
thermostability in relation to ionic strength. The maximal lipase activity (1585 U/L) was obtained whenPenicillium citrinum was cultured on 0.75% ammonium sulfate complemented with minerals salts instead of yeast extract. Although this activity
was about 55% lower than that produced in medium with yeast extract (2850 U/L), the specific activity (7.8 U/mg proteins)
was higher than that obtained with the yeast extract (4.9 U/mg proteins). The morphology of fungus changed totally, with yeast
extract there are smooth, solid, and spherical pellets whereas on ammonium sulfate there are small “hairy” pellets uniformly
suspended in the medium. The effect of ferrous (Fe++) ions was carried out using medium MA with and without Fe++ ions. Lipase production byPenicillium citrinum in medium MA requires Fe++ ions, the absence of which caused a decreased of about 50% in the specific activity (3.5 U/mg proteins). The utilization
of commercial, locally available oils as carbon sources, such as soybean oil (236 U/L) and corn oil (74 U/L) resulted in lower
activity compared to olive oil, showing that lipase production byPenicillium citrinum is specifically induced by olive oil. Potassium concentration in the medium can effects the production of lipase (1 mM (1585
U/L), 10 mM (1290 U/L), and 30 mM (1238 U/L), 50 mM (195 U/L), and 100 mM (2 U/L). The crude culture filtered was susceptable
to thermal deactivation. It was stable at pH 6.0, but was not stable at the optimum pH (8.0-8.5) at 50 mM. At the low ionic
concentration (1-25 mM) this lipase was stable at low pH (3.5-4.0). The activation energy was 22.4 ±2.2 Kcal. mol 1. 相似文献
895.
IMPROVED PROPERTIES OF METALLOCENE-CATALYZED LINEAR LOW-DENSITY POLYETHYLENE/POLYPROPYLENE BLENDS DURING ULTRASONIC EXTRUSION 总被引:1,自引:0,他引:1
Hong Wu Shao-yun Guo 《高分子科学》2007,(4):357-364
Metallocene-catalyzed linear low-density polyethylene/polypropylene (mLLDPE/PP) blends were prepared by ultrasonic extrusion in this work. Their extrusion processing behaviors were estimated by online measured data, such as the die pressure and flow rate. Crystallization and mechanical properties of the blends were also investigated. The results show that the addition of PP improves the processing behaviors of mLLDPE, but has little effect on its mechanical properties. On the other hand, the addition of mLLDPE improves the impact strength of PP, but has little effect on its processing behavior. The processing behaviors and mechanical properties of mLLDPE/PP blends get further improved due to the presence of ultrasonic oscillation during extrusion. Compared with PP-rich blends, the apparent viscosity drop of mLLDPE-rich blends is more sensitive to ultrasonic oscillation. The ultrasonic oscillation affects the crystal nucleation, while barely the other crystalline behaviors of the blends. 相似文献
896.
Summary. Phenoxyacetic acid distribution in two-phase systems n-aliphatic hydrocarbon (C5–C8) – water and its dimerization in organic phase were investigated. The values of distribution coefficient (D
HR), distribution constant (K
D), and dimerization constant (K
dim) of acid were obtained. The empirical correlations of these quantities with Hildebrand solubility parameter of organic solvents were established. The influence of pH of the aqueous phase as well as the polarity of the applied organic solvents on phenoxyacetic acid physical chemistry in
the two-phase systems was described. 相似文献
897.
MingZhuLIU ShengYiZHANG YuHuaSHEN MingLiangZHANG 《中国化学快报》2004,15(10):1249-1252
Selenium nanoparticles were prepared by a reverse microemulsion system. Sodium selenosulfate was used as selenium source. The results showed that hydrochloric acid concentration and reaction temperature had great influence on the morphology of products. The crystalline selenium nanowires and amorphous selenium nanorods were obtained in given condition. 相似文献
898.
Hiromu Hayashi 《Catalysis Surveys from Japan》1999,3(1):43-52
Additive telluromolybdates, MoO3·2TeO2 and MIIO·TeO2·MoO3 (MIITeMoO6; MII = Co, Mn, Zn), converted ethyl lactate selectively to pyruvate in a vaporphase fixedbed flow system at 250–300 °C. A synergy in activity was observed for binary TeO2–MoO3, and crystalline Te2MoO7 was suggested as the active species. The Rietveld analysis of powder XRD patterns of ternary CoTeMoO6 revealed the layer structure quite different from that of the reference Te2MoO7, but tellurium was again located adjacent to molybdenum linked through lattice oxygen. 相似文献
899.
The possibility of humic acids acting as micellar phase in micellar electrokinetic chromatography was evaluated. We investigated the separation of naphthalene in capillary electrophoresis using various samples of humic acids as micellar phase under different pH conditions, concentrations of humic acid, and temperature. The humic acid samples studied were from different origins including peat, vermicompost and a commercial sample acquired from Aldrich. Methanol was used as a marker for the electroosmotic flow. The results indicate that the formation of micelle depends on the number and nature of the hydrophobic association sites in an aqueous humic acid solution and on the origin and concentration of the humic acid at a defined pH. At lower pH values, the possibility of the humic acid molecule forming pseudomicelles increases due to a combination of neutralized and dissociated charged sites. 相似文献
900.
The rectifying junction characteristics of the organic compound pyronine-B film on a p-type Si substrate has been studied. The pyronine-B has been sublimed on the top of p-Si surface. The barrier height and ideality factor values of 0.79±0.04 and 1.13±0.06 eV for this structure have been obtained from the forward bias current-voltage (I-V) characteristics. From the low capacitance-frequency (C-f) characteristics as well as conductance-frequency (G-f) characteristics, the energy distribution of the interface states and their relaxation time have been determined in the energy range of (0.53−Ev)-(0.79−Ev) eV taking into account the forward bias I-V data. The interface state density Nss ranges from 4.93×1010 cm−2 eV−1 in (0.79−Ev) eV to 3.67×1013 cm−2 eV−1 in (0.53−Ev) eV. Furthermore, the relaxation ranges from 3.80×10−3 s in (0.53−Ev) eV to 4.21×10−4 s in (0.79−Ev) eV. It has been seen that the interface state density has an exponential rise with bias from the midgap towards the top of the valence band. The relaxation time shows a slow exponential rise with bias from the top of the valence band towards the midgap. 相似文献