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101.
Edward E. Flagg Donald L. Schmidt 《Journal of polymer science. Part A, Polymer chemistry》1970,8(1):1-14
Poly[tris(diorganophosphinato)alanes], [Al(OPRR′O)3]n, were synthesized in which the organic moieties (R,R′) contained from one to eighteen carbon atoms. Polymeric properties depended upon the organic moieties; polymers were fusible, tractable, and flexible when the organic moieties contained six or more carbon atoms. Soluble polymers were prepared by using mixtures of symmetrical and unsymmetrical phosphinates. One polymer, poly{bis[n-butyl(benzyl)phosphinato]di-n-octylphosphinatoalane}, exhibited a degree of polymerization greater than 1000 and an exceptionally high intrinsic viscosity of 37 dl/g. The properties of the different polymers are discussed, and feasible structures are proposed. 相似文献
102.
103.
Funyu S Isobe T Takagi S Tryk DA Inoue H 《Journal of the American Chemical Society》2003,125(19):5734-5740
Visible light irradiation of a reaction mixture of carbonyl-coordinated tetra(2,4,6-trimethyl)phenylporphyrinatoruthenium(II) (Ru(II)TMP(CO)) as a photosensitizer, hexachloroplatinate(IV) as an electron acceptor, and an alkene in alkaline aqueous acetonitrile induces selective epoxidation of the alkene with high quantum yield (Phi = 0.6, selectivity = 94.4% for cyclohexene and Phi = 0.4, selectivity = 99.7% for norbornene) under degassed conditions. The oxygen atom of the epoxide was confirmed to come from a water molecule by an experiment with H(2)(18)O. cis-Stilbene was converted into its epoxide, cis-stilbeneoxide, without forming trans-stilbeneoxide. trans-Stilbene, however, did not exhibit any reactivity. Under neutral conditions, an efficient buildup of the cation radical of Ru(II)TMP(CO) was observed at the early stage of the photoreaction, while an addition of hydroxide ion caused a rapid reaction with the cation radical to promote the reaction with reversion to the starting Ru(II)TMP(CO). A possible involvement of a higher oxidized state of Ru such as Ru(IV), Ru(V), Ru(VI) through a dismutation of the Ru(III) species was excluded by an experiment with Ru(VI)TMP(O)(2). Decarbonylation of the Ru complex was also proven to be invalid. A reaction mechanism involving an electron transfer from the excited triplet state of Ru(II)TMP(CO) to hexachloroplatinate(IV) and subsequent formation of OH(-)-coordinated Ru(III) species, leading to an oxo-ruthenium complex as the key intermediate of the photochemical epoxidation, was postulated. 相似文献
104.
Our recently proposed scheme for including aqueous solvation free energies in parameterized NDDO SCF models is extended to the Parameterized Model 3 semiempirical Hamiltonian. The solvation model takes accurate account of the hydrophobic effect for hydrocarbons, as well as electric polarization of the solvent, the free energy of cavitation, and dispersion interactions. Eight heteroatoms are included (along with H and C), and the new model is parameterized accurately for the water molecule itself, which allows meaningful treatments of specifically hydrogen bonded water molecules. The unphysical partial charges on nitrogen atoms predicted by the Parameterized Model 3 Hamiltonian limit the accuracy of the predicted solvation energies for some compounds containing nitrogen, but the model may be very useful for other systems, especially those for which PM3 is preferred over AM1 for the solute properties of the particular system under study. © 1992 by John Wiley & Sons, Inc. 相似文献
105.
106.
A method for the simultaneous determination of trace concentrations of saturated and α,β-unsaturated carbonyl compounds in complex systems is presented. Carbonyl as the alkaline 2,4-dinitrophenylhydrazone is determined spectrophotometrically at 2 selected wavelengths of 480 and 426 nm. The apparent total carbonyl concentration is obtained from prepared calibration curves at the selected wavelengths based on known concentrations of n-heptaldehyde. From the observed relative response of known concentrations of n-heptaldehyde and 2-ethyl-2-hexenal, the true concentration for saturated and α,β-unsaturated carbonyl is obtained by a simple calculation. The method has been used extensively for alcohol systems ranging up to tetracontanol but is equally useful for hydrocarbons, aromatic oxygenates and hydrocarbons, petroleum distillates and kerosenes, organic acids and esters, and some ethers. 相似文献
107.
Donald I. Hoke Donald L. Surbey William R. Oviatt 《Journal of polymer science. Part A, Polymer chemistry》1972,10(2):595-604
A series of N-(dialkylaminoalkyl)acrylamides was synthesized by reductive amination of N-(1,1-dimethyl-3-oxobutyl)acrylamide (diacetone acrylamide) and by the reaction of either an alkenylamine or an amino alcohol with acrylonitrile. These monomers homopolymerize and copolymerize readily to form high molecular weight products. The solubility of the monomers and their homopolymers in water ranges from soluble to insoluble at room temperature. The insoluble materials can be quaternized readily to produce water-soluble products. The solubility of the homopolymers in water decreases with increasing temperature. Glass transition and decomposition temperatures of the homopolymers are reported. 相似文献
108.
Ultrafiltration fractionation and liquid chromatography (LC) have been applied to the study of the binding and hydrolysis of the polar herbicide atrazine on a stoichiometrically well characterized fulvic acid. Binding requires extensive carboxylate site protonation but the binding sites represent a very small fraction of total carboxylate. The data show that binding of atrazine is not competitive with binding of the hydrolytic product hydroxyatrazine. However, smaller molecular weight fractions of the fulvic acid mixture compete with atrazine for sites on the larger molecular weight fraction. Binding equilibrium is not rapid. A model of binding involving hydrogen bonding and/or charge-transfer complexing to specific sites created dynamically by the conformational equilibria of the higher molecular weight polymeric fulvic acid fractions is proposed as the best accommodation of the variety of observed facts. 相似文献
109.
Kenneth K. Chan Donald D. Giannini Anne H. Cain John D. Roberts William Porter William F. Trager 《Tetrahedron》1977,33(8):899-906
Fourier-transform 13C NMR spectra of nine coumarinoid compounds of medicinal interest are reported. All of the carbon resonances are assigned with the aid of various spectral techniques and stable isotopic labeling. The substituent effects on the chemical shifts in several systems are also discussed. 相似文献
110.
Lonnon DG Craig DC Colbran SB Bernhardt PV 《Dalton transactions (Cambridge, England : 2003)》2004,(5):778-787
Copper(II) bromide and chloride complexes of the new heptadentate ligand 2,6-bis(bis(2-pyridylmethyl)amino)methylpyridine (L) have been prepared. For the bromide complexes, chains of novel, approximately C2-symmetric, chiral [Cu2(L)Br2]2+ 'wedge-shaped' tectons are found. The links between the dicopper tectons and the overall chirality and packing of the chains are dictated by the bromide ion content, not the counter anion. In contrast, the chloride complexes exhibit linked asymmetric [Cu2(L)Cl3]+ tectons with distinct N3CuCl2 and N4CuCl2 centres in the solid. The overall structures of the dicopper bromide and chloride units persist in solution irrespective of the halide. The redox chemistry of the various species is also described. 相似文献