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1.
Michael P. Hartshorn Richard G. Jensen A. Grant Waller Graeme J. Wright 《Tetrahedron letters》1987,28(52):6701-6704
Reaction of the 15N-4-nitrodienone (1) with excess nitrogen dioxide in benzene for 16 h gives the 4,5,6-trinitro ketone (2), labelled (15NO2) at C6 but not at C4, and recovered 4-nitrodienone (1) in which extensive loss of 15NO2 has occurred. The mechanistic implications of these and related results are discussed. 相似文献
2.
The determination of seven saponins in crude plant extracts by electrospray ionization mass spectrometry (ESI-MS) and fast atom bombardment mass spectrometry (FAB-MS) is described. Distinct protonated and natriated (Na-adduct) molecular ions in ESI-MS spectra readily provide molecular weight information, which can be further verified using clusters of molecular ions. Saponin mixtures can be analyzed by ESIMS on varying the potential difference between the capillary and skimmer in the ESI source to decompose impurities. ESI-MS uses less amount of sample than that required by FAB-MS. ESI-MS does not produce structural information, however. The FAB-MS spectra consist mainly of protonated and deprotonated molecular ions with limited structural information. (-)-FAB-MS is more suitable for analyzing saponin samples than the (+)-FAB-MS. 相似文献
3.
Mark P. Waller Thomas Dresselhaus Jack Yang 《Journal of computational chemistry》2013,34(16):1420-1428
Here, we present just a collection of beans (JACOB): an integrated batch‐based framework designed for the rapid development of computational chemistry applications. The framework expedites developer productivity by handling the generic infrastructure tier, and can be easily extended by user‐specific scientific code. Paradigms from enterprise software engineering were rigorously applied to create a scalable, testable, secure, and robust framework. A centralized web application is used to configure and control the operation of the framework. The application‐programming interface provides a set of generic tools for processing large‐scale noninteractive jobs (e.g., systematic studies), or for coordinating systems integration (e.g., complex workflows). The code for the JACOB framework is open sourced and is available at: www.wallerlab.org/jacob . © 2013 Wiley Periodicals, Inc. 相似文献
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Mass spectral analysis of carbohydrates has become an important tool for the biological chemist1–3 and the use of mass spectrometers interfaced with gas-liquid chromatographs has provided a convenient method of study for volatile derivatives of carbohydrates. Several groups4–7 have accomplished separations of the various isomeric trimethylsilyl (TMSi) esters and ethers of the glucuronic acids. The present work utilizes a gas-liquid chromatograph-mass spectrometer to examine the previously unreported mass spectra of pertrimethylsilylated glucuronic acids and these spectra are compared to the previously reported8 spectra of the pemethylated glucuronic acids. 相似文献
6.
Arlanda Huffer Ben Jeffery Benjamin J. Waller Andreas A. Danopoulos 《Comptes Rendus Chimie》2013,16(6):557-565
A method for the synthesis and isolation of 1,1′-methylene-bis-(3-aryl-imidazol-2-ylidene) ligands, aryl = 2,6-diisopropyl-phenyl (DiPP), LDiPP, mesityl (mes), Lmes, is reported, which provides synthetically useful quantities of high purity. Derivatisation of LDiPP with chalcogenides gave the adducts LDiPPE2, E = S, Se, Te. Reaction of LDiPP with [Pd(tmeda)Me2], [Pt(μ-SMe2)Me2]2, [Ir(1,5-COD)(μ-Cl)]2/KPF6 and [NiBr2(dme)] gave [Pd(LDiPP)Me2] (1), [Pt(LDiPP)Me2] (2), [Ir(LDiPP)(1,5-COD)](PF6) (3) and [Ni(LDiPP)Br2] (4), respectively. The latter was reduced in the presence of CO to [Ni(LDiPP)(CO)2] (5). The structures of Lmes, LDiPPTe2, and 1–5 are also reported. 相似文献
7.
Waller MP Howard ST Platts JA Piltz RO Willock DJ Hibbs DE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(29):7603-7614
The charge distribution of taurine (2-aminoethane-sulfonic acid) is revisited by using an orbital-based method that describes the density in a fixed molecular orbital basis with variable orbital occupation numbers. A new neutron data set is also employed to explore whether this improves the deconvolution of thermal motion and charge density. A range of molecular properties that are novel for experimentally determined charge densities are computed, including Weinhold population analysis, Mayer bond orders, and local kinetic energy densities, in addition to charge topological analysis and quantum theory of atoms-in-molecules (QTAIM) integrated properties. The ease with which a distributed multipole analysis can be performed on the fitted density matrix makes it straightforward to compute molecular moments, the lattice energy, and the electrostatic interaction energies of molecules removed from the crystal. Results are compared with high-level (QCISD) gas-phase calculations and band structure calculations employing density functional theory. Finally, the avenues available for extending the range of molecular properties that can be calculated from experimental charge densities still further using this approach are discussed. 相似文献
8.
The metal content of a series of contaminated sediments has been determined by equilibrating ion-exchange resins of different types (held in porous cages) with aqueous suspensions of the sediments. H(+)-form exchangers took up high proportions of the Cu, Pb, Zn and Cd contents with recoveries depending on whether the acid functional groups were strong. Na(+)-form exchangers took up a smaller, loosely bound, labile fraction. The metal ions held on the exchangers were back-extracted into 0.05M EDTA and determined by flame AAS. Dissolution of sediment components led to the exchangers also taking up large amounts of Ca, Mg, Fe and Al. The exchange-resin technique provides an alternative means of subdividing the metal content of sediments into different "labile" or "available" fractions. Possible advantages include minimal re-adsorption of released metal ions by the sediment phases, retention of only "labile" species (ions or complexes), and a transfer mechanism which may resemble the action of plant roots more closely than chemical extractant processes do. 相似文献
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John?Bartley Thomas?Soltau Hereward?Wimborne Sunjun?Kim Angeline?Martin-Studdard David?Hess William?Hill Jennifer?Waller James?CarrollEmail author 《BMC neuroscience》2005,6(1):15