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《Tetrahedron letters》1987,28(45):5551-5554
The direct metalation of several p-hydroxybenzylmethyl ethers has been studied. Those substrates possesing an electron-withdrawing group in a 1,3 relationship with the coordinating (-CH2OMe) group underwent regioselective metalation by the action of n-BuLi/THF. Highly substituted phenols can thus be readly prepared. 相似文献
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M. Skowrońska-Ptasińska K.B. Starowieyski S. Pasynkiewicz M. Carewska 《Journal of organometallic chemistry》1978,160(2):403-409
Reactions of Me3Al, i-Bu3Al, Me2AlCl and Me2AlCCMe with 2,6-di-t-butyl-4-methylphenol have been studied at different molar ratios of the reactants.It is found that in the reaction with the phenol, trimethylaluminium forms monomeric methylaluminium diphenoxide; triisobutylaluminium gives both monomeric mono- and di-phenoxyaluminium (depending on molar ratios of the reactants) and dimethylchloroaluminium forms dimeric methylphenoxyaluminium chloride.It is found that methylpropynylaluminium phenoxide is unstable and disproportionates in hydrocarbon solutions.The mechanisms of some of these reactions are suggested. 相似文献
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The present paper is complementary to the foregoing reviews and describes some additional methods of the derivatization of particular functional groups mainly to enhance the structural information content of electron ionization and chemical ionization mass spectra. Derivatization approaches for the modification of unsaturated compounds, alcoholic, carboxylic, carbonyl, amine and other functional groups, are discussed. Derivatization for separation and quantitative determination of chiral enantiomeric compounds is also considered. Preliminary chemical and physicalchemical degradation for structure elucidation of high molecular weight compounds (biopolymers, synthetic polymers) is mentioned. Chemical aspects of derivatizations and characteristic mass spectral features of derivatives are described briefly. Some particular applications of chemical modification, in conjunction with mass spectral measurements for the analysis of various important bioorganic compounds and compounds in biological fluids, air, environmental etc., are considered. 相似文献
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The results of heats of mixing experiments on a series of ortho-substituted phenols with an amide or an ester are described. Substituents were chosen to span a wide range of electronic and steric character. Enthalpy of mixing results do not correlate solely with the acid strength of the phenol, or with a Hammett linear free-energy analysis. Rather, interactions are favored by the presence of groups with the ability to weaken the base strength of the proton donor while simultaneously increasing its acid strength. Such groups share a combination of electron-withdrawing ability and/or steric bulk that causes an effective decrease in the electron density about the phenolic oxygen. Trifluoromethyl and tert-butyl, and to a lesser extent halogen and hydroxy substituents ortho to the phenolic OH, give the highest exothermic enthalpies of mixing and are thus the most effective at promoting intermolecular interactions with weak bases such as amides and esters. These results should be useful in designing miscible or compatible polymer blends in which specific interactions such as hydrogen bonding are important. © 1995 John Wiley & Sons, Inc. 相似文献
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T. I. Davidenko Yu. E. Shapiro I. A. Kravchenko O. V. Sevast'yanov V. Ya. Gorbatyuk S. P. Krasnoshchekaya 《Russian Chemical Bulletin》1996,45(9):2136-2140
Intercalation compounds of phenols and poly-N-vinylcaprolactam (PVC) form when their aqueous solutions are mixed. Using13C NMR and IR spectroscopy complexation was shown to proceed through the formation of hydrogen bonds between the carbonyl groups of the caprolactam moieties and phenolic hydroxyls as well as through displacement of water from the polymer structure and its compaction. The processes of the formation of intercalation compounds of PVC with phenol andtert-butyl alcohol were compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2251–2255, September, 1996. 相似文献
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The following compounds of methanesulfonic acid, CH3SO3H, have been prepared: Cu(CH3SO3)2 · 4 H2O; Zn(CH3SO3)2 · 4 H2O; Mn(CH3SO3)2 · 2 H2O; Cd(CH3SO3)2 · 2 H2O and Ag(CH3SO3). Their thermal behavior has been studied using TG and DTA, together with X-ray analysis of the solid products formed during the heating. The water of hydration is evolved in one step (Mn, Cd) or in two step (Cu, Zn). The intermediate hydrates and the anhydrous salts are crystallized. The anhydrous Zn, Ag and Cd compounds melt, the anhydrous Cd salt undergoing a polymorphic transition before melting. They then begin to decompose in the temperature range 325–440°C. Under an inert atmosphere, the decomposition yields well-crystallized residues of various composition: Cu + Cu2S; Ag + Ag2S (the sulfides being in very minute amounts); MnS; CdS; ZnO + ZnS. 相似文献
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Recent developments in the understanding of the biosynthesis of the active site of the nitrogenase enzyme, the structure of the iron centre of [Fe]-hydrogenase and the structure and biomimetic chemistry of the [FeFe] hydrogenase H-cluster as deduced by application of X-ray spectroscopy are reviewed. The techniques central to this work include X-ray absorption spectroscopy either in the form of extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES) and nuclear resonant vibrational spectroscopy (NRVS). Examples of the advances in the understanding of the chemistry of the system through integration of a range of spectroscopic and computational techniques with X-ray spectroscopy are highlighted. The critical role played by ab initio calculation of structural and spectroscopic properties of transition-metal compounds using density functional theory (DFT) is illustrated both by the calculation of nuclear resonance vibrational spectroscopy (NRVS) spectra and the structures and spectra of intermediates through the catalytic reactions of hydrogenase model compounds. 相似文献
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