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51.
52.
Tran Quang Minh Léon Christiaens Pierre Grandclaudon Alain Lablache-Combier 《Tetrahedron》1977,33(17):2225-2229
Photoirradiated in presence of acetophenone, benzo[b]selenophene and its 3-methyl derivative add to dimethyl acetylenedicarboxylate. In each ease, the primary reaction product is unstable and has not been isolated. Photoexeited in its triplet state (the energy of which is in the neighbourhood of 69 ) benzo[b]selenophene and its 2- and 3-methyl, 2,3 dimethyl, 3 acetoxy and 2-methyl-3-acetoxy derivatives add to 1,2 dichloroethylene leading to cyclobutanes. Neither cyclo-addition occurs in absence of photosensitiser. Single-crystal X-ray analysis gave the structures of the two adducts of 3-acetoxybenzo[b]selenophene with trans-1,2-dichloroethylene. In both compounds the chlorine atoms are trans. 相似文献
53.
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57.
Jocelyn Jalbert Roland Gilbert Pierre Tétreault Brigitte Morin Denise Lessard-Déziel 《Cellulose (London, England)》2007,14(4):295-309
In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by
the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative
conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture
of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the
number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded
(TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper
constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the
system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial
moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular
chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing
transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of
equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and
TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential
over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with
2-furfuraldehyde, which is the current reference in the domain. 相似文献
58.
Fadila Balegroune Pierre Braunstein Laurent Douce Yves Dusausoy Daniel Grandjean Michael Knorr Martin Strampfer 《Journal of Cluster Science》1992,3(3):275-296
The reactions of K[Fe{Si(OMe)3}(CO)3(PY)][PY=Ph2PCH2C(O)Ph, Ph2PCH2C(O)[(-C5H4)FeCp] (Cp=5-C5H5), Ph2P(CH2)2CN] with CdCl2·2.5H2O, ZnX
2 (X=Cl, I) or InCl3 afforded Fe-Cd-Fe or Fe-M(-X)2
M-Fe (M=Cd, Zn, In;X=Cl, I) and Fe-InCl2 complexes. Some of them contain an unusual and labile -2-SiO alkoxysilyl bridge which may be associated with a bridging mode for the ketophosphine ligand (first such example structurally established), thus providing original results in bimetallic chemistry on the intramolecular coordination of oxygendonor functions ofchemically different hemilabile ligands firmly attached to a neighboring metal center. The structures of the trinuclear complex (3), of the chlorobenzene solvate of the tetranuclear complex (4a·C6H5Cl) and of [mer-(OC)3{(EtO)3Si} (4e) have been determined by X-ray diffraction. Crystals of 3 are orthorhombic, space groupPbcn, witha=19.010(4),b=11.766(5),c=26.998(7)Å, andZ=4. Crystals of4a·C6H5Cl are monoclinic, space groupC2/c witha=22.455(3),b=17.680(2),c=16.627(4)Å, =90.80(4)°, andZ=4. Crystals of4e are monoclinic, space groupC2/c witha=25.392(5),b=18.554(6),c=16.28(1)Å, =120.73(3)°, andZ=4. The structures were solved using direct methods and Fourier difference techniques and refined by blocked full-matrix least squares toR=0.035 (R
w
=0.049) for 2719 observed reflections, toR=0.042 (R
w
=0.056) for 3082 observed reflections, and toR=0.057 (R
w
=0.075) for 1850 observed reflections for3, 4a·C6H5Cl and4e, respectively. The Fe-Zn complexes (9a), (9b) and (9c) were prepared and characterized by spectroscopic methods.Part 21 in the Series: Complexes with Functional Phosphines. Part 20: P. Braunstein, S. Coco Cea, A. DeCian, and J. Fischer (1992).Inorg. Chem.
31, 4203. 相似文献
59.
Christian Bellec Marie-Claude Bellassoued-Fargeau Bernadette Graffe Marie-Claude Sacquet Pierre Maitte 《Journal of heterocyclic chemistry》1990,27(3):551-555
The chemical reduction of 5H-[1]benzopyranno[4,3-d]pyrimidines with lithium aluminum hydrrde leads to 3,4-dihydro derivations. The electro-chemical reducation in acidic medium shows two monoelectronic cathodic waves. In netural or basic medium, substituted compounds in 2 position show a single bielectronic wave while two bielectronic waves are observed for unsubstituted compounds In all cases, preparative electrolysis lead to a hydrodimer in the 4,4′-positiom. 相似文献
60.
Groothaert MH Smeets PJ Sels BF Jacobs PA Schoonheydt RA 《Journal of the American Chemical Society》2005,127(5):1394-1395
This work reports on the capability of the O2-activated Cu-ZSM-5 and Cu-MOR zeolites to selectively convert methane into methanol at a temperature of 398 K. A strong correlation between (i) the activity and (ii) the intensity of the 22 700 cm-1 UV-vis band, assigned to the bis(mu-oxo)dicopper core, is found (i) as a function of the reaction temperature, (ii) as a function of the Cu loading of the zeolite, and (iii) in comparison to other Cu materials. These three lines of evidence firmly support the key role of the bis(mu-oxo)dicopper core in this selective, low-temperature hydroxylation of methane. 相似文献