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Reaction of the isodicyclopentadienide anion and its dehydro congener with Fe(II) leads to a stereochemically homogeneous ferrocene derivative in each instance. Through chemical correlation and X-ray analysis, above-plane complexation is established for both halves within the two sandwich compounds. 相似文献
23.
[reaction: see text] A zirconocene-mediated ring contraction of 4-vinylfuranosides generated either from d-arabinose or d-glucose is followed by sequential oxidation to the ketone and alkynyl Grignard addition. The resulting cis-cyclobutanediols are subjected in turn to thermal rearrangement and intramolecular oxymercuration-demercuration. The regiochemistry of the final ring closure is controlled by the nature of R. 相似文献
24.
Carbonnelle S Loco JV Overmeire IV Windal I Wouwe NV Leeuwen SV Goeyens L 《Talanta》2004,63(5):1255-1259
Differences between chemical activated luciferase gene expression (CALUX) bioassay and chemoanalyses results are observed.This paper shows that calculations of the TEQ values using REP values instead of WHO TEF values give different results. The REP values do affect the results obtained by the CALUX technique. These differences are more marked for the dioxin like PCB compounds (CALUX TEQ values are lower than WHO TEQ values) than for the dioxin compounds (CALUX TEQ values are higher than WHO TEQ values).The CALUX results were compared with the concentrations of the congeners’ spiked into the oil. 相似文献
25.
Nineteen sulphonated 2-hydroxybenzophenones and three sulphonated 2,2′-dihydroxybenzophenones have been prepared and compared with a commercially available member of each class of uv absorber as photo-protective agents for wool. Treated fabrics were exposed to Philips ML G/74 lamps and the extent of photo-tendering was assessed by measuring breaking loads and tear strengths. In general, 2-hydroxybenzophenones with 3-alkyl substituents provide better protection against photo-tendering than absorbers lacking 3-alkyl substituents. 2,2′-Dihydroxybenzophenones are more effective than 2-hydroxybenzophenones.
On the basis of effectiveness and ease of synthesis, 2,2′-dihydroxy-4,4′-bis-w-sulphobutyloxybenzophenone (VIIb) shows most promise as a photo-protective agent. At the 5% level of application it trebles the lifetime of wool fabric during exposure to sunlight through window glass. It also retards the photo-tendering and fading of wool fabrics containing either a red or a blue milling acid dye. 相似文献
26.
The conductances of aqueous CaCl2, Ca(CH3COO)2, and Ca(CH3COO)2.nCH3COOH were measured from 348 to 523 K at pressures near 10 MPa using a flow conductometric technique. The first association constant for calcium chloride and the first and second association constants for calcium acetate in water, were derived from a least-squares fit of the measurements to a conductance model in which activity coefficients were calculated using the mean spherical approximation (MSA) and the conductance was modeled by the Turq, Blum, Bernard, and Kunz (TBBK) equation, plus a mixture model. 相似文献
27.
An activated D-residue of a protected dipeptide when coupled racemizes twice as much as an activated L-residue, which is contrary to the case for couplings of acylamino acids. 相似文献
28.
The mass spectra of several dibenzo (d.f)-1,3,2,-dioxaphosphorepines of the type where X=0, S, Se and R=2,2′-biphenylylene, have been studied. Dibenzochalcogen ions [RX]+˙ stemming directly from [M]+˙ were observed with high intensities, indicating specific migration of X from phosphorus to carbon with simultaneous destruction of the dioxaphosphorepine ring. Simple cleavage of P? Y as usually observed in similar organophosphorus compounds is not a common process here. 相似文献
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