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91.
Acecyclone and related cyclopentadienones 11 react with dimethyl tricyclo[4.2.0.02,5]deca-3,7,9-triene-7, 8-dicarboxylate 1 in refluxing xylene to afford the cyclo-octatetraenes 12, via a sequence involving [4+2]π-cycloaddition, cheletropic loss of carbon monoxide, extrusion of dimethyl phthalate by [4+2]π-cycloreversion, and finally valence isomerisation by retro-6π electrocyclisation. NMR evidence indicates that the products 12 contain rigid, bond-fixed, non-planar cyclo-octatetraene rings. 相似文献
92.
Miroslawa El Fray Agnieszka Pilaszkiewicz Krzysztof J. Kurzydlowski 《European Polymer Journal》2007,43(5):2035-2040
The morphology of hydrogels based on poly(vinyl alcohol) (PVA) in their frozen hydrated state, modified with biologically active di- and multifunctional molecules was studied by scanning electron microscopy (SEM) with cryo-attachment. The porosity of samples was found to be more regular and ordered in the case of samples containing difunctional, and especially multifunctional carboxylic acids as compared to the neat PVA hydrogel. The morphology is dependent not only from the hydrogel composition but also the number of freezing-thawing cycles. Resulted highly porous and oriented structure has significant influence on materials properties, such as compressive stress and crosslinking density. 相似文献
93.
David J. Augeri Andrew H. Fray Edward F. Kleinman 《Journal of heterocyclic chemistry》1990,27(5):1509-1511
The 2,3-dehydro analog 2 of the potent quinolone antibacterial agent ofloxacin ( 1 ) was synthesized by an efficient six step route beginning with ethyl 2,3,4,5-tetrafluorobenzoylacetate. Formation of the oxazine ring of 2 was accomplished by ozonolysis of 1-(1-buten-3-yl)quinolone 5 to the corresponding aldehyde, which cyclized upon treatment with base via intramolecular displacement of the C-8 fluorine to afford tricyclic ester 6 . The antibacterial activities of 2,3-dehydroofloxacin ( 2 ) and ofloxacin ( 1 ) are compared. 相似文献
94.
95.
Syntheses of the two stereoisomeric 10-hydroxydec-2-enoic acids are described. The trans-isomer is identical with the main fatty acid isolated from royal jelly of honeybees.
Some compounds closely related to this trans-acid have also been prepared.
A convenient process for the preparation of 10-acetoxy-decanoic acid from castor oil has been developed. 相似文献
96.
A novel humidity sensor operating at T<580K using Yb-doped SrCeO3 ionic conductor with a Au-Pd chemical filter has been developed. In this unique design, both the electrodes are exposed to
the same test gas and therefore do not require separation of working and reference compartments. A thin layer of impervious
Au-Pd alloy on one surface of the perovskite electrolyte allows selective access to oxygen gas, while the other surface coated
with porous Pt is exposed to both H2O and oxygen. Sensor emfs are found to be directly proportional to log pH2O and independent of pO2. The design aspects of the sensor, the experimental set-up, some typical results and a postulated mechanism of sensor operation
are described in this paper.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
97.
G. I. Fray 《Tetrahedron》1961,14(3-4):161-163
The original observation that 3(or 5)-methylcyclopent-2-en-2-ol-1-one (I) was formed (in low yield) by the treatment of glycidaldehyde with acetone in the presence of aqueous alkali, and speculations concerning the reaction mechanism, led to the realization that the reaction could also be carried out with glyceraldehyde. This suggested an explanation for the previously known formation of I by drastic alkali-treatment of carbohydrates. 相似文献
98.
99.
Sodium metal is an excellent reductant and can be used to reduce most metallic chlorides and many oxides. However, sodium
is relatively expensive and is hazardous to store so that it is only used to reduce titanium tetrachloride to titanium. In-situ
electrolytic preparation of sodium from sodium chloride in a reactor is difficult due to the evolution of chlorine, another
hazardous substance.
A novel cell is described where the sodium salt is separated from the salt to be reduced by a sodium beta alumina membrane.
The anode is in the sodium salt and the cathode is in the metallic salt and, on the application of current, it has been found
that the metal ions are reduced to the metal and the anion in the sodium salt is oxidised. By using sodium hydroxide or sodium
carbonate as the sodium salt, the anodic products are oxygen and water vapour or oxygen and carbon dioxide.
Examples are given of electrolytic cells incorporating beta alumina membranes for the production of magnesium and zirconium
from the chlorides where the metal is produced and the anodic gases are not toxic. Overall these cells are very efficient
as the anodic and cathodic products are separated by the beta alumina membrane and compared with existing cells some of the
electrical energy requirement is replaced by chemical energy. The environmental benefits of these cells are very attractive
for the production of reactive metals on a small scale.
Paper presented at the 4th Euroconference on Solid State Ionics, Connemara, Galway, Ireland, Sept. 13–19, 1997 相似文献
100.