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141.
E. Makrlík P. Vaňura P. Selucky Z. Spíchal 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(1):13-18
Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of 1,2-(diphenylphosphino)ethane dioxide (DPPEtDO, L) has been investigated. The equilibrium data have been
explained assuming that the species HL+, HL2
+, ML2
3+ and ML4
3+ (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated
with water have been determined. It was found that the stability constants of the corresponding complexes EuL
n
3+ and AmL
n
3+, where n = 2, 4 and L is DPPEtDO, in water-saturated nitrobenzene are comparable. 相似文献
142.
Stanis?aw Krompiec Mateusz Penkala Ewelina Kowalska Robert Penczek Piotr Bujak Witold Danikiewicz Grzegorz Spólnik Andrzej Kita Iwona Grudzka 《Monatshefte für Chemie / Chemical Monthly》2011,33(7):1241-1247
Abstract
Ru-catalyzed synthesis of mixed alkyl–alkyl acetals via addition of primary alcohols to allyl ethers has been extended to include long-chain and/or functionalized substrates. The catalytic systems for these reactions were generated from RuCl2(PPh3)3 and [RuCl2(1,5-COD)]x and phosphines [PPh3 or P(p-chlorophenyl)3] or SbPh3. Of particular importance is the almost quantitative elimination of transacetalization. The addition proceeds through allyl complexes, not via isomerization of allyl ethers––subsequent addition of ROH to vinyl ethers. 相似文献143.
Ottosson N Børve KJ Spångberg D Bergersen H Sæthre LJ Faubel M Pokapanich W Öhrwall G Björneholm O Winter B 《Journal of the American Chemical Society》2011,133(9):3120-3130
The local electronic structure of glycine in neutral, basic, and acidic aqueous solution is studied experimentally by X-ray photoelectron spectroscopy and theoretically by molecular dynamics simulations accompanied by first-principle electronic structure and spectrum calculations. Measured and computed nitrogen and carbon 1s binding energies are assigned to different local atomic environments, which are shown to be sensitive to the protonation/deprotonation of the amino and carboxyl functional groups at different pH values. We report the first accurate computation of core-level chemical shifts of an aqueous solute in various protonation states and explicitly show how the distributions of photoelectron binding energies (core-level peak widths) are related to the details of the hydrogen bond configurations, i.e. the geometries of the water solvation shell and the associated electronic screening. The comparison between the experiments and calculations further enables the separation of protonation-induced (covalent) and solvent-induced (electrostatic) screening contributions to the chemical shifts in the aqueous phase. The present core-level line shape analysis facilitates an accurate interpretation of photoelectron spectra from larger biomolecular solutes than glycine. 相似文献
144.
Structures of tert-butylcarbamate ions in the gas-phase and methanol solution were studied for simple secondary and tertiary carbamates as well as for carbamate-containing products and internal standards for lysosomal enzyme assays used in newborn screening of a α-galactosidase A deficiency (Fabry disease), mucopolysaccharidosis I (Hurler disease), and mucopolysaccharidosis II (Hunter disease). The protonation of simple t-butylcarbamates can occur at the carbonyl group, which is the preferred site in the gas phase. Protonation in methanol solution is more favorable if occurring at the carbamate nitrogen atom. The protonation of more complex t-butylcarbamates occurs at amide and carbamate carbonyl groups, and the ions are stabilized by intramolecular hydrogen bonding, which is affected by solvation. Tertiary carbamates containing aminophenol amide groups were calculated to have substantially greater gas-phase basicities than secondary carbamates containing coumarin amide groups. The main diagnostically important ion dissociation by elimination of 2-methylpropene (isobutylene, i-C(4)H(8)) and carbon dioxide is shown by experiment and theory to proceed in two steps. Energy-resolved collision-induced dissociation of the Hurler's disease enzymatic product ion, which is a coumarin-diamine linker-t-butylcarbamate conjugate (3a(+)), indicated separate energy thresholds for the loss of i-C(4)H(8) and CO(2). Computational investigation of the potential energy surface along two presumed reaction pathways indicated kinetic preference for the migration of a t-butyl hydrogen atom to the carbamate carbonyl resulting in the isobutylene loss. The consequent loss of CO(2) required further proton migrations that had to overcome energy barriers. 相似文献
145.
146.
Aurel Sp?taru 《Statistics & probability letters》2011,81(10):1547-1551
Let X,X1,X2,… be i.i.d. random variables, and set Sn=X1+?+Xn. We prove that for three important distributions of X, namely normal, exponential and geometric, series of the type ∑n≥1anP(|Sn|≥xbn) or ∑n≥1anP(Sn≥xbn) behave like their first term as x→∞. 相似文献
147.
Zapadlo M Krupčík J Kovalczuk T Májek P Spánik I Armstrong DW Sandra P 《Journal of chromatography. A》2011,1218(5):746-751
A total of 196 out of 209 polychlorobiphenyl (PCB) congeners were resolved using GC×GC-TOFMS with a non-polar/ionic liquid column series consisting of poly(50%-n-octyl-50%-methyl)siloxane and (1,12-di(tripropylphosphonium)dodecane bis(trifluoromethansulfonyl)amide) in the first and second dimension, respectively. It has been found that 13 PCB congeners overlap in five doublets (CB12+CB13, CB62+CB75, CB70+CB76, CB97+CB125 and CB153+CB168) and one triplet (CB90+CB101+CB113). All toxic, "dioxin like" congeners were separated with no interferences from any PCB congener. The 109 PCBs present in Aroclor 1242 and the 82 PCBs present in Aroclor 1260 were resolved GC×GC-TOFMS analysis on this column set. 相似文献
148.
Kwon TH Armel V Nattestad A Macfarlane DR Bach U Lind SJ Gordon KC Tang W Jones DJ Holmes AB 《The Journal of organic chemistry》2011,76(10):4088-4093
A one-pot synthesis of 2,6-dibromodithieno[3,2-b;2',3'-d]thiophene (dibromo-DTT, 4) was developed. A key step was bromodecarboxylation of DTT-2,6-dicarboxylic acid, obtained by saponification of the diester 1. The donor-acceptor dye DAHTDTT (13), based on a central 2,6-bis[2'-(3'-hexylthienyl)]dithieno[3,2-b;2',3'-d]thiophene core (9), was prepared and incorporated in a dye-sensitized solar cell (DSC), which exhibited an energy conversion efficiency of 7.3% with V(oc) of 697 mV, J(sc) of 14.4 mA/cm(2), and ff of 0.73 at 1 sun. 相似文献
149.
150.