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Shailesh K. Goswami Lyall R. Hanton C. John McAdam Stephen C. Moratti Jim Simpson 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(4):407-411
The title compounds, C11H11BrO3, (I), and C11H11NO5, (II), respectively, are derivatives of 6‐hydroxy‐5,7,8‐trimethylchroman‐2‐one substituted at the 5‐position by a Br atom in (I) and by a nitro group in (II). The pyranone rings in both molecules adopt half‐chair conformations, and intramolecular O—H...Br [in (I)] and O—H...Onitro [in (II)] hydrogen bonds affect the dispositions of the hydroxy groups. Classical intermolecular O—H...O hydrogen bonds are found in both molecules but play quite dissimilar roles in the crystal structures. In (I), O—H...O hydrogen bonds form zigzag C(9) chains of molecules along the a axis. Because of the tetragonal symmetry, similar chains also form along b. In (II), however, similar contacts involving an O atom of the nitro group form inversion dimers and generate R22(12) rings. These also result in a close intermolecular O...O contact of 2.686 (4) Å. For (I), four additional C—H...O hydrogen bonds combine with π–π stacking interactions between the benzene rings to build an extensive three‐dimensional network with molecules stacked along the c axis. The packing in (II) is much simpler and centres on the inversion dimers formed through O—H...O contacts. These dimers are stacked through additional C—H...O hydrogen bonds, and further weak C—H...O interactions generate a three‐dimensional network of dimer stacks. 相似文献
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Macha SF Limbach PA Hanton SD Owens KG 《Journal of the American Society for Mass Spectrometry》2001,12(6):732-743
Potential difficulties associated with background silver salt clusters during matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of nonpolar polymers are reported. Silver salt cluster ions were observed from m/z 1500 to 7000 when acidic, polar matrices, such as 2,5-dihydroxybenzoic acid (DHB), all-trans-retinoic acid (RTA) or 2-(4-hydroxyphenylazo)benzoic acid (HABA), were used for the analysis of nonpolar polymers. These background signals could be greatly reduced or eliminated by the use of nonpolar matrices such as anthracene or pyrene. Representative examples of these background interferences are demonstrated during the analysis of low molecular weight nonpolar polymers including polybutadiene and polystyrene. Nonpolar polymers analyzed with acidic, polar matrices (e.g., RTA) and silver cationization reagents can yield lower quality mass spectral results when interferences due to silver clusters are present. Replacing the polar matrices with nonpolar matrices or the silver salts with copper salts substantially improved the quality of the analytical results. In addition, it was found that silver contamination cannot be completely removed from standard stainless steel sample plates, although the presence of silver contamination was greatly reduced after thorough cleaning of the sample plate with aluminum oxide grit. Carry-over silver may cationize polymer samples and complicate the interpretation of data obtained using nonpolar matrices in the absence of added cationization reagents. 相似文献
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Scott D. Hanton James R. Stets 《Journal of the American Society for Mass Spectrometry》2009,20(6):1115-1118
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is an important technique to characterize many different
materials, including synthetic polymers. MALDI mass spectral data is used to determine the polymer average molecular weights,
repeat units, and end groups. The development of the vortex method of solvent-free sample preparation showed that remarkably
short mixing times could prepare samples that yielded high quality MALDI mass spectra. In this paper, we use microscopy images
and MALDI mass spectra to evaluate the mixing time required by the vortex method to produce mass spectra for low molecular
mass polymer samples. Our results show that mixing times of as little as 10 s can generate homogeneous thin films that produce
high quality mass spectra with S/N ∼ 100. In addition, ultrashort mixing times of only 2 s still produce samples with mostly
smooth morphology and mass spectra with S/N ∼ 10. 相似文献
5.
Theresa Hague Andrea Petroczi Paul LR Andrews James Barker Declan P Naughton 《Chemistry Central journal》2010,4(1):2
This is a correction to the following paper: Hague T, Petroczi A, Andrews PR, Barker J, Naughton DP: Determination of metal
ion content of beverages and estimation of target hazard quotients: a comparative study. Chem Central J 2008, 2:13. 相似文献
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A tripodal sulfur ligand for the selective ruthenium-catalysed hydrogenation of dimethyl oxalate 总被引:1,自引:0,他引:1
Boardman B Hanton MJ van Rensburg H Tooze RP 《Chemical communications (Cambridge, England)》2006,(21):2289-2291
The first example of a catalyst utilising a sulfur-based ligand [MeC(CH2SBu)3] for the selective hydrogenation of dimethyl oxalate to methyl glycolate is reported. 相似文献
7.
Hanton SD McEvoy TM Stets JR 《Journal of the American Society for Mass Spectrometry》2008,19(6):874-881
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is an important technique to characterize many different materials, including synthetic polymers. MALDI mass spectral data can be used to determine the polymer average molecular weights, repeat units, and end groups. The development of solvent-free sample preparation methods has enabled MALDI to analyze insoluble materials and, interestingly, can provide higher-quality mass spectral data. Although the utility of solvent-free sample preparation for MALDI has been demonstrated, the reasons for its success are only now being discovered. In this study, we use microscopy tools to image samples prepared using solvent-free methods to examine the morphology of these samples. The samples are prepared using a simple vortex method. Our results show that the average particle size of typical MALDI matrices is reduced from their original tens to hundreds of micrometers to hundreds of nanometers. This size reduction of the matrix occurs in one minute using the vortex method. We also observe remarkably smooth and homogeneous sample morphologies for the laser to interrogate, especially considering the relatively crude methods used to prepare our samples. 相似文献
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A one pot, multi-component CuAAC reaction has been developed for the generation of alkyl, benzyl or aryl substituted bi and tridentate pyridyl-1,2,3-triazole ligands from their corresponding halides, sodium azide and alkynes in excellent yields. The ligands have been fully characterized by elemental analysis, HR-ESMS, IR, 1H and 13C NMR and in the ferrocenyl substituted cases the structures were confirmed by X-ray crystallography. Additionally, we have examined the coordination chemistry of these ligands and found that a variety of geometrically diverse Cu(II) and Ag(I) complexes, including interesting tri and tetrasilver complexes, can be formed. 相似文献
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M. Barth C. De Clercq E. De Wolf J. J. Dumont D. P. Johnson J. Lemonne P. Peeters R. Contri H. Drevermann L. Gerdyukov Y. Goldschmidt-Clermont G. Harigel J. Joensuu C. Milstene J. P. Porte R. T. Ross M. Spyropoulou-Stassinaki C. Caso F. Fontanelli R. Monge S. Squarcia U. Trevisan J. F. Baland J. Beaufays F. Grard J. Hanton P. A. Van der Poel L. Gatignon W. Kittel W. J. Metzger D. J. Schotanus A. Stergiou R. T. Van de Walle Y. Belokopitov V. Brizgalov P. Chliapnikov A. Fenuyk V. Kubic E. Krytchenko S. Lugovsky V. Nikolaenko J. Petrovikh V. Ronjin O. Tchikilev V. Yarba V. Zjigunov 《Zeitschrift fur Physik C Particles and Fields》1981,7(2):89-96
The inclusive inelastic processesK + p→pX + andK + p→Δ ++ X 0 are studied at an incident momentum of 70 GeV/c. The data comes from the Big European Bubble Chamber BEBC filled with hydrogen, exposed to an rf reparatedK + beam at the CERN SPS accelerator. The inclusive cross section for protons with laboratory momentump LAB≦1.2 GeV/c is equal to (6.1±0.1) mb. InclusiveΔ ++-production is studied for |t p, Δ|<1.0(GeV/c)2. Comparisons are made with otherK + p data and withpp data at 69 GeV/c. Evidence is found for Pomeron exchange at the beam vertex both for slow proton andΔ ++-production as well as for absorptive pion exchange at the (p,Δ ++) vertex. 相似文献
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I. V. Ajinenko Y. A. Belokopitov P. V. Chliapnikov V. P. Falaleev A. B. Fenyuk L. N. Gerdyukov A. I. Kurnosenko A. M. Rybin E. A. De Wolf J. J. Dumont M. Gysen M. Van Immerseel F. Grard J. Hanton J. Laberrigue H. K. Nguyen C. Cochet M. L. Faccini-Turluer L. Mosca France-Soviet Union Collaboration CERN-Soviet Union Collaboration 《Zeitschrift fur Physik C Particles and Fields》1980,4(3):181-199
Final data on topological cross sections are presented. Inclusive single particle distributions for the reactionsK + p→ π± X at 32 GeV/c are discussed and compared with data at lower energies. Early scaling in the fragmentation regions is confirmed, while cross sections in th central region continue to rise with energy even faster than inpp interactions. Thex-andp T -dependence of the π+/π? ratio inK + p interactions is discussed and a comparison of reactionsK + p→ π± X andK ? p→ π± X at 32 GeV/c is made in the context of constituent models. We also present transverse momentum distributions, show prominent seagull effects and study how they are influenced by resonance production. 相似文献