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621.
G. v. Hevesv R. Hobbie L. C. Hurd F. Reynolds L. Losana M. Jarach G. Dotreppe M. L. Holt N. S. Ssingalowski und P. M. Porchunow 《Fresenius' Journal of Analytical Chemistry》1935,101(5-6):195-199
Ohne Zusammenfassung 相似文献
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Treatment of alpha,alpha-dichloroaldehydes with various phenols in the presence of chiral triazolium salt catalysts and excess base results in the synthesis of alpha-chloro aryl esters in good yield and enantioselectivity. The reaction is tolerant of various functionality on the aldehyde as well as several electronically diverse phenols. The product chloroesters were further transformed into chloroacid, chlorohydrin, and azidoesters with nearly complete retention of enantioselectivity. 相似文献
625.
Cary DR Zaitseva NP Gray K O'Day KE Darrow CB Lane SM Peyser TA Satcher JH Van Antwerp WP Nelson AJ Reynolds JG 《Inorganic chemistry》2002,41(6):1662-1669
Bipyridine ligands containing pendant methyl, amino, and amino-boronic acid groups were synthesized. Coordination complexes of these ligands with rhenium were prepared straightforwardly and in good yield. The fluorescence behavior of the Re complexes was studied as a function of pH and exposure to various concentrations of glucose. The methyl bipyridine complex showed no change in fluorescence with pH, the amino derivative showed a rapid decrease from low pH to neutral, and the amino-boronate derivative showed little change from pH 4 to 10. Fluorescence quenching was observed at high pH as expected on the basis of a photoinduced electron transfer (PET) signaling mechanism. This behavior can be explained on the basis of the first oxidation and reduction potentials of these complexes. Glucose testing showed a significant dependence on the solvent system used. In pure methanol, the rhenium boronate complex exhibited a 55% fluorescence intensity increase upon increasing glucose concentration from 0 to 400 mg/dL. However, in 50 vol % methanol/phosphate buffered saline, none of the complexes showed significant response in the glucose range of physiological interest. 相似文献
626.
Reconstructions of a three-dimensional absorber embedded in a scattering medium by use of frequency domain measurements of the transmitted light in a single source-detector plane are presented. The reconstruction algorithm uses Bayesian regularization and iterative coordinate descent optimization, and it incorporates estimation of the detector noise level, the source-detector coupling coefficient, and the background diffusion coefficient in addition to the absorption image. The use of multiple modulation frequencies is also investigated. The results demonstrate the utility of this algorithm, the importance of a three-dimensional model, and that out-of-plane scattering permits recovery of three-dimensional features from measurements in a single plane. 相似文献
627.
13C T1 relaxation times have been determined for n-butanol in C6D12 in the concentration range 0.001 ? x ? 1 (using 13C labelled alcohol) and for t-butanol in the range 0.01 ? x ? 1. In the former case, this has allowed us to probe molecular mobility down to the region of monomeric alcohols. Comparison with previous results from measurements of 1H chemical shifts, dielectric relaxation, and the picosecond dynamics of electron solvation allows us to build up a detailed picture of molecular clustering and liquid structure in alkane—alcohol mixtures. For n-butanol, the local liquid structure is established by x = 0.2 while t-butanol does not appear to form aggregates larger than trimers until x = 0.5. 相似文献
628.
The rate constants for the replacement of water from the inner-coordination shell of Co(NH3)5OH23+, I, by dimethyl sulfoxide (DMSO) as DMSO gradually replaced water in the solvation shell of I were found to approach, and finally equal, the water-exchange rate constant of I in aqueous media in accordance with expectation for a dissociative mechanism. Also the rate constants for the replacement of DMSO from the innercoordination shell of Co(NH3)5DMSO3+, II, by water as water replaced DMSO in the solvation shell of II were found to approach, and approximately equal, the DMSO-exchange rate constant for II in liquid DMSO in accordance with expectation for a dissociative mechanism. The DMSO-exchange rate constant for II in liquid DMSO was determined and found to be equal to (3.6 ± 0.8) × 10?4 sec?1 at 45°C. The dissociation quotient, [II] [NO3?]/[Co(NH3)5NO32+], was found to be equal to 0.28 ± 0.11 M at 45°C by NMR methods. The pseudo first-order rate constants for anation of II by NO3? and the solvation of Co(NH3)5NO3 2+ by DMSO were determined at various temperatures. 相似文献
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