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31.
Automated selective iodometric methods for the determination of chlorine and oxychlorine species have been developed for use in the drinking water industry. By utilising kinetic-based methods, linear ranges observed were: chlorine, 0.2–10 mg l?1; chlorine dioxide, 0.3–10 mg l?1; chlorite ion, 0.08–5 mg l?1; and chlorate ion, 0.08–5 mg l?1. 相似文献
32.
C. G. Overberger Gordon M. Parker 《Journal of polymer science. Part A, Polymer chemistry》1968,6(3):513-526
Three new, optically active, methyl-substituted 2-oxohexamethyleneimines were prepared by cyclization of the respective optically active C-methylated 6-aminohexanoic acids. The active forms of the amino acids used for the preparation of (?)-3-methyl-2-oxohexamethyleneimine and (?)-7-methyl-2-oxohexamethyleneimine were obtained by resolution of their diastereomeric quinine salts. s-(+)-5-methyl-2-oxohexamethyleneimine was synthesized without racemization from optically pure 2-isopropylidene-5-methyleyclohexanone (pulegone). 相似文献
33.
Enhanced fluorescence from arrays of nanoholes in a gold film 总被引:1,自引:0,他引:1
Brolo AG Kwok SC Moffitt MG Gordon R Riordon J Kavanagh KL 《Journal of the American Chemical Society》2005,127(42):14936-14941
Arrays of sub-wavelength holes (nanoholes) in gold films were used as a substrate for enhanced fluorescence spectroscopy. Seven arrays of nanoholes with distinct periodicities (distances between the holes) were fabricated. The arrays were then spin-coated with polystyrene films containing different concentrations of the fluorescent dye oxazine 720. The dye was excited via resonant extraordinary transmission of the laser source through the nanoholes. Enhanced fluorescence was observed when the geometric characteristics of the arrays allowed for an enhancement in the transmitted excitation. This enhancement occurred via surface plasmon excitation by the laser and a consequential increase in the local electromagnetic field in a sub-wavelength region at the metal-film interface. It was demonstrated that the sensitivity of the fluorescence measurement (change in signal vs change in dye concentration in the polymer film) is significantly larger at the surface plasmon resonance conditions than that obtained from equivalent films on glass substrates. Enhancement factors for the fluorescence emission were calculated for each array, with a maximum enhancement of close to 2 orders of magnitude as compared to the emission of films on glass. The results presented here indicate that arrays of nanoholes are interesting substrates for the development of fluorescence sensors based on surface plasmon resonance, as they provide a platform that allows both spatial confinement and enhancement of excitation light. Moreover, the collinear characteristics of the present optical setup, due to the resonant extraordinary transmission through the nanohole arrays, are more conducive to miniaturization and chip integration than more traditional experimental geometries. 相似文献
34.
Aristides Christofides Miguel Ciriano John L. Spencer F. Gordon A. Stone 《Journal of organometallic chemistry》1979,178(1):273-280
The compounds [Pt(C2H4)2(PR3)] [PR3 = P-tBu2Me, P(C6H11)3, PPh3] react dimethyldivinylsilane or dimethyldivinyltin to give chelate complexes [Pt{(CH2CH)2MMe2} (PR3)] (M = Si or Sn). allyltrimethyltin reacts with various diethylene (tertiary phosphine)platinum compounds with cleavage of the allyl group to afford complexes [Pt(SnMe3)(η3-C3H5)(PR2)]. The NMR spectra (13C, 1H and 31P) of the new compounds have been recorded, and the data are discussed in terms of the structures proposed. 相似文献
35.
D. H. Beebe C. E. Gordon R. N. Thudium M. C. Throckmorton T. L. Hanlon 《Journal of polymer science. Part A, Polymer chemistry》1978,16(9):2285-2301
A quantitative procedure has been developed for characterizing the complete microstructure of polymers of 1,3-pentadiene, including the tacticity of any crystalline component. This can be accomplished by a combination of infrared spectroscopy, X-ray crystallinity, and 300-MHz NMR spectroscopy. A series of high structural purity polymers were synthesized with a series of previously unreported mixed microstructures. These samples were characterized by using the three techniques mentioned, including the previously unreported 300-MHz NMR data. With those results a 60-MHz NMR/IR method of spectroscopy was developed to determine the composition of poly(1,3-pentadiene)s in terms of percent cis-1,2-, cis-1,4-, trans-1,4-, and 3,4-pentadiene units. 相似文献
36.
Hale KJ Frigerio M Manaviazar S Hummersone MG Fillingham IJ Barsukov IG Damblon CF Gescher A Roberts GC 《Organic letters》2003,5(4):499-502
[structure: see text] The synthesis of two truncated bryostatin analogues 2 and 3 is described. High-field NMR measurements on the C-ring analogue 3 in C(2)H(3)CN containing 25% (2)H(2)O have shown that it binds to the CRD2 of human PKC-alpha at virtually the same position as phorbol-13-acetate (PA) and bryostatin 1 (1). NMR titration studies have also revealed that 3 binds to the CRD2 with a potency similar in magnitude to PA but much less potently than 1. 相似文献
37.
Garth R. Giesbrecht Gavin E. Collis John C. Gordon David L. Clark Brian L. Scott Ned J. Hardman 《Journal of organometallic chemistry》2004,689(13):2177-2185
Use of the bulky cyclopentadienyl ligand [η5-C5H2(SiMe3)3-1,2,4]− (Cp?) allows for the isolation of monomeric, mono-ring lanthanide species. As previously reported, (Cp?)K reacts with LaI3(THF)4 (THF=tetrahydrofuran) in THF/pyridine to form the mono-ring complex (Cp?)LaI2(py)3 (1) (py=pyridine); a minor product of this reaction is the bis-ring species (Cp?)2LaI(py) (2). The solid state structure of 2 reveals a monomeric compound containing a pseudo-tetrahedral metal center exhibiting no unusual intramolecular contacts. Addition of one equiv of KNHAr (Ar=2,6-iPr2C6H3) to complex 1 in THF generates the mono-anilido compound (Cp?)LaI(NHAr)(THF)2 (3), which may be converted to the more stable pyridine adduct (Cp?)LaI(NHAr)(py)2 (4) by the addition of pyridine to 3. An X-ray crystal structure of 3 indicated a trigonal bipyramidal metal center with the anilido group oriented trans to the iodide atom (N1-La1-I1=123.1(3)°). A structural study on the bis-pyridine adduct 4 revealed a similar Cs-symmetric structure with a slightly increased Nanilido-La-I angle of 132.1(2)°. Addition of KNHAr to the di-iodo bipyridine adduct (Cp?)LaI2(bipy)(py) (5), in which the two iodide atoms are cis-disposed, yields the mono-anilido complex (Cp?)LaI(NHAr)(bipy)(py) (6) (bipy=2,2′-bipyridine); this compound may also be prepared by the addition of bipy to (Cp?)LaI(NHAr)(py)2 (4). An X-ray diffraction study shows that the lanthanum center in 6 is octahedrally coordinated by a Cp? ring, an iodide, an anilido group, a pyridine molecule and two nitrogens of a bipy molecule. In this case, the anilido moiety and the iodide ligand are arranged in a cis fashion (Nanilido-La-I=111.2(2)°), resulting in a complex with C1 symmetry. Both (Cp?)LaI(NHAr)(py)2 (4) and (Cp?)LaI(NHAr)(bipy)(py) (6) are inactive as catalysts for the hydroamination/cyclization of 2-amino-hex-5-ene. 相似文献
38.
A simple relationship is derived which expresses the change in oscillation frequency of a quartz crystal in contact with a fluid in terms of material parameters of the fluid and the quartz. The relationship is Δf = ?f0(ηL?L/πμQ?Q), where f0 is the oscillation frequency of the free (dry) crystal, ηL and ?L are the absolute viscosity and density of the liquid, respectively, and μQ and ?Q are the elastic modulus and density of the quartz. This relation is obtained from a simple physical model which couples the shear wave in the quartz to a damped shear wave in the fluid. Quantitative comparisons with two test cases, aqueous solutions of glucose and ethanol at various concentrations, demonstrate the accuracy of this model. 相似文献
39.
Magnetically recoverable chiral catalysts immobilized on magnetite nanoparticles for asymmetric hydrogenation of aromatic ketones 总被引:1,自引:0,他引:1
Novel heterogenized asymmetric catalysts were synthesized by immobilizing preformed Ru catalysts on magnetite nanoparticles via the phosphonate functionality and were characterized by a variety of techniques, including TEM, magnetization, and XRD. These nanoparticle-supported chiral catalysts were used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with very high enantiomeric excess values of up to 98.0%. The immobilized catalysts were easily recycled by magnetic decantation and reused for up to 14 times without loss of activity and enantioselectivity. Orthogonal nature of the present catalyst immobilization approach should allow the design of other superparamagnetic nanoparticle-supported asymmetric catalysts for a wide range of organic transformations. 相似文献
40.
Summary Pentacoordinated molecules are thought to undergo intramolecular isomerization by the widely accepted Berry pseudorotation mechanism. Through our investigations, we have found that the actual pseudorotation for the PH4F system is more complex than that envisioned by Berry. The potential energy surface of PH4F is mapped out at the RHF/6-311G(d, p) level. According to the Berry mechanism, this system is expected to have two minima and two maxima; however, the system actually has two transition states and one global minimum. The minimum energy path from the highest transition state is followed to the second transition state, which in turn has a minimum energy path leading to the global minimum. Along the path between the two transition states there is a branching region. This portion of the potential energy surface is probed extensively.Dedicated to Prof. Klaus Ruedenberg 相似文献