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81.
Jarroux N Keller P Mingotaud AF Mingotaud C Sykes C 《Journal of the American Chemical Society》2004,126(49):15958-15959
A new inisurf (acting as surfactant and initiator) molecule for ring-opening metathesis polymerization (ROMP) was synthesized and used in aqueous solution in order to control the size and shape of polymer nodules grown from liposomes. Nodules were observed to grow in size with conversion of monomer, and depending on the monomer used, they adopted either a spherical or comet-like shape. Here, we investigate polymer production from a liposome surface. We use a hydrophobic derivative of the Grubbs catalyst positioned at the liposome surface to allow for ROMP of monomers dissolved in the aqueous outer phase. We obtain nodules of polymer that can grow up to tens of micrometers, unveiling new efficient possibilities of polymerization from a membrane in an aqueous solution. 相似文献
82.
Cheeseman M Feuillet FJ Johnson AL Bull SD 《Chemical communications (Cambridge, England)》2005,(18):2372-2374
A new way of combining chiral auxiliaries and substrate-directable reactions for asymmetric synthesis is described that employs a three-step sequence of aldol-cyclopropanation-retro-aldol reactions for the stereoselective synthesis of enantiopure cyclopropane carboxaldehydes. 相似文献
83.
In solution, the [(tim)Co](2+) complex (tim = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) reacts only slowly with O(2), but upon adsorption on graphite electrodes, it becomes an active catalyst for the reduction of O(2) to H(2)O(2). The electroreduction of O(2) proceeds in a single voltammetric step at close to the diffusion-controlled rate at a relatively positive potential (0.25 V vs SCE). The remarkable enhancement in catalytic activity is attributed to a higher affinity for O(2) of the adsorbed complex as a result of its interactions with functional groups on the surface of roughened or oxidized graphite. A possible mechanism for the catalytic reduction of O(2) is proposed. It differs from the one employed by the analogous [(hmc)Co](2+) complex (hmc = C-meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) which operates at less positive potentials and exhibits two separated voltammetric steps in the reduction of O(2), via [(hmc)CoOOH](2+), to H(2)O(2). 相似文献
84.
Fernandes SA Nachtigall FF Lazzarotto M Fujiwara FY Marsaioli AJ 《Magnetic resonance in chemistry : MRC》2005,43(5):398-404
'Non-covalent synthesis' of novel chiral hosts (calix[6]arene-chiral amine complexes) and its application to enantiomeric discrimination was investigated by (1)H NMR spectroscopy. The topology of a ternary complex was proposed for the calix[6]arene-amine-sulfoxide to rationalize the chiral recognition. 相似文献
85.
Gerhard Holxe Titus A. Jenny Petr Nesvadba Albert Gossauer Ludger Ernst Walter Keller Christoph Kratky 《Helvetica chimica acta》1991,74(6):1287-1295
On treatment with H2SO4/MeOH, epimerization of hexamethyl cis-5,6-dihydroxycobyrinate c,8-lactam ( 3 ) takes place quantitatively at C(6), yielding the corresponding trans-diol 4 . The corresponding lactone 7 , whose structure has been established by X-ray analysis, is obtained from xanthocorrinoids 5 and 6 under similar conditions. 相似文献
86.
M. J. Folkes A. Keller J. Stejny P. L. Goggin G. V. Fraser P. J. Hendra 《Colloid and polymer science》1975,253(5):354-361
The recently observed very low-frequencyRaman bands in polyethylene open up the possibility of determining the straight-chain stem lengths within the crystal as opposed to the full periodicity constituted by crystal core plus amorphous surface layer given by lowangle X-ray diffraction. Past works (6–10) have established the correlation with lamellar thickness but leave doubts about the possibility of making the distinction just indicated. The first objective of the present work was to examine this point on crystals where the chains are inclined to different extents with respect to the lamellar surface. The samples include single-crystals grown from solution at different temperatures and oriented bulk polyethylenes. It is concluded that the low-frequencyRaman peaks correspond to the inclined chain length as opposed to the layer thickness, hence providing a measure of a chain as opposed to a platelet property. TheRaman based length figures are only slightly below those of the appropriately inclined straight traverses across the full lamellae, hence on the basis of existing understanding non-trans chain sequences are confined to a surface region which must be much narrower than required by the usually envisaged amorphous crystalline two-phase structure. Similar studies were carried out also on single crystals of the linear polyester poly(decamethylene sebacate). These demonstrate in the first place that polymers other than polyethylene can also be amenable to suchRaman studies and secondly that in this particular instance, changes in the relative thicknesses of crystal core and surface layer could be registered. The two studies in conjunction affirm the potential of the low-frequencyRaman technique for the study of polymer crystal morphology. 相似文献
87.
Beltrami I Bylsma BG DeBonte R Gan KK Koltick D Loeffler FJ Low EH McIlwain RL Miller DH Ng CR Ong PP Rangan LK Shibata EI Wilson RJ Derrick M Fernandez E Fries R Hyman L Kooijman P Loos JS Musgrave B Price LE Schlereth J Sugano K Weiss JM Wood DE Baranko G Baringer P Blockus D Brabson B Forden GE Gray SW Jung C Neal H Ogren H Rust DR Valdata-Nappi M Akerlof C Bonvicini G Chapman J Errede D Harnew N Kesten P Kooijman S Meyer DI Nitz D Rubin D Seidl AA Thun R Trinko T Willutzky W Cork B Keller L 《Physical review letters》1985,54(16):1775-1778
88.
G. Münzenberg S. Hofmann H. Folger F. P. Heßberger J. Keller K. Poppensieker B. Quint W. Reisdorf K. H. Schmidt H. J. Schött P. Armbruster M. E. Leino R. Hingmann 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(2):227-235
In irradiations of207Pb and208Pb, respectively, with54Cr theα-decay of the isotopes259106,260106, and261106 could be observed for the first time. For260106 a spontaneous fission branch of (50 ?20 +30 )% was observed. The isotopes were identified by genetic relationships of α-decay after separation in-flight with the velocity filter SHIP and implantation into a position-sensitive silicon surface-barrier detector. The measured partial fission halflife of the doubly even isotope260106 of (7.2 ?2.7 +4.8 )ms exceeds the predicted values by at least a factor of 40. This result could be explained by the high shell corrections of the ground state mass, derived from the measured α-decay energies. The experimental results show evidence for an island of purely shell stabilized nuclei in the region of deformed isotopes beyond the actinides. 相似文献
89.
90.
α-(α'-Bromobenzyl)chalcone ( 3 ) reacts with primary amines (t-butyl, isopropyl,cyclohexyl) to give α-(α'-alkylaminobenzyl)chalcones ( 4, 5 and 6 ). When these allylic amines are treated with hydrogen bromide followed by reaction with base, they produce l-alkyl-2,4-diphenyl-3-benzoyl-azetidines ( 7,8 and 9 ). These azetidines were readily converted to their 3-deuterio derivatives ( 10 , 11 and 12 ) by treatment with sodium methoxide in deuteriomethanol. The configurations were assigned primarily by pmr spectra and mass spectra in reference to analogous compounds. 相似文献