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141.
Getzler YD Mahadevan V Lobkovsky EB Coates GW 《Journal of the American Chemical Society》2002,124(7):1174-1175
A new highly active and selective catalyst for the synthesis of beta-lactones from CO and epoxides is reported. The catalyst, [(N,N'-bis(3,5-di-tert-butylsalicylidene) phenylenediamino)Al(THF)2][Co(CO)4] ([(salph)Al(THF)2][Co(CO)4]) is easily prepared from the corresponding (salph)AlCl and NaCo(CO)4. At 50 degrees C and 880 psi of CO, the catalyst (1 mol %) carbonylates epoxides such as propylene oxide, 1-butene oxide, epichlorohydrin, and isobutylene oxide to the lactones beta-butyrolactone, beta-valerolactone, gamma-chloro-beta-butyrolactone, and beta-methyl-beta-butyrolactone in high yield. (R)-Propylene oxide was carbonylated to (R)-beta-butyrolactone with retention of stereochemistry. 相似文献
142.
Erioglaucine A, Eriogreen B, Patent Blue and Xylene Cyanol FF work satisfactorily for the titration of Sb(III) with Ce(IV) in 1-2N sulphuric acid medium with iodine as catalyst. In hydrochloric acid medium the colour of the oxidized dye is very evanescent but is very much improved in intensity and stability by the addition of manganese(II) sulphate; no catalyst is needed. 相似文献
143.
144.
Vinod Viswanath Vincent Vineeth Leo S. Sabna Prabha C. Prabhakumari M.S. Jisha 《Natural product research》2016,30(2):223-227
The chemical nature of the polyphenols of cashew kernel testa has been determined. Testa contains tannins, which present large molecular complexity and has an ancient use as tanning agents. The use of tannins extracted from cashew testa, considered in many places as a waste, grants an extra value to the cashew. In this work we have analysed through high performance liquid chromatography, infrared spectroscopy (FT-IR) and thermo gravimetric analysis the average molecular weight, main functional groups and thermal properties of tannins extracted from Anacardium occidentale L. The results of these analyses are compared with the commercial grade tannic acid. The FT-IR spectra showed bands characteristic of C = C, C–C and OH bonds. This important bioactive compound present in the cashew nut kernel testa was suggested as an interesting economical source of antioxidants for use in the food and nutraceutical industry. 相似文献
145.
J. Thimmasetty C. V. S. Subrahmanyam P. R. Sathesh Babu M. A. Maulik B. A. Viswanath 《Journal of solution chemistry》2008,37(10):1365-1378
The solubility behavior of pimozide in individual solvents ranging from nonpolar to highly polar was studied. For understanding
the solute-solvent interactions, the partial solubility parameters concept was utilized. Solutions containing excess drug
were shaken in a water bath for 72 hours at 25 °C. After the solutions attained equilibrium, they were filtered and analyzed
for drug content. A multiple regression method, using extended Hansen’s partial solubility parameters, was applied to verify
the solubilities of pimozide in pure polar and nonpolar solvents and to predict its solubility in untested solvents. The three-parameter
approach and the Flory-Huggins size correction term ‘B’ give predictions of solubilities with correlations up to 97%. The four-parameter approach involving proton-donor and proton-acceptor
parameters was also used in fitting the solubility data. The correlations are appreciable (94%). Further, the ‘B’ term coupled with four-parameter approach was examined in order to improve the data representation, and resulted in a 1%
improvement (98%) in the correlation when compared to the Flory-Huggins size-correction method. The solubility parameter obtained
by this method is 10.43 H which is closer to the values obtained by theoretical methods, such as Fedors’ and Hoy’s. The resulting
partial solubility parameters are δ
2d
=8.85 H, δ
2p
=2.17 H, δ
2a
=3.15 H, and δ
2b
=4.08 H, which give insights into the interaction capability of pimozide and are consistent with its chemical structure. Pimozide
is a Lewis base as its δ
2b
>δ
2a
. The total solubility parameter of pimozide is assigned at 10.43 H. This work demonstrates for the first time the validity
of the four-parameter approach coupled with the Flory-Huggins size-correction term and therefore the result is interesting. 相似文献
146.
Analytical instruments that can measure small amounts of chemicals in complicated biological samples are often useful as diagnostic tools. However, it can be challenging to optimize these sensors using actual clinical samples, given the heterogeneous background and composition of the test materials. Here we use gas chromatography-differential mobility spectrometry (GC/DMS) to analyze the chemical content of human exhaled breath condensate (EBC). Ultimately, this system can be used for non-invasive disease diagnostics. Many parameters can be adjusted within this instrument system, and we implemented a factorial design-of-experiments to systematically test several combinations of parameter settings while concurrently analyzing effects and interactions.We examined four parameters that affect sensitivity and detection for our instrument, requiring a 24 factorial design. We optimized sensor function using EBC samples spiked with acetone, a known clinical biomarker in breath. Two outputs were recorded for each experiment combination: number of chemicals detected, and the amplitude of acetone signal. Our goal is to find the best parameter combination that yields the highest acetone peak while also preserving the largest number of other chemical peaks in the spectra. By optimizing the system, we can conduct further clinical experiments with our sensor more efficiently and accurately. 相似文献
147.
148.
Trupti A. Chavan Nicy Ajith Remya Devi Periyamana Sankaran nampoothiri Kallola Kumar Swain 《X射线光谱测定》2019,48(3):208-217
The various factors affecting energy dispersive X-ray fluorescence determination of iron in solid powder samples were evaluated, to improve the quality of these measurements. Influence of samples/standards preparation and instrumental parameters such as applied voltage to the X-ray tube, tube output current, and duration of acquisition were assessed, and the optimized instrumental parameters were 12 kV, 200 μA, and 200 s, respectively. Linear dynamic range of the spectrometer was found to be 0.0052 to 5.042 g kg−1. Detection limits of iron in various organic/inorganic samples were found to be 2.5 to 21.9 mg kg−1. The values obtained during the present method were evaluated with neutron activation analysis. 相似文献
149.
150.
Nissy Ann Harry Sankaran Radhika Mohan Neetha Gopinathan Anilkumar 《Journal of heterocyclic chemistry》2020,57(4):2037-2043
A rapid, efficient, and green grinding assisted method for the synthesis of 2,3-dihydro-1H-perimidines has been developed. 1,8-Diaminonaphthalene and aldehydes were ground using mortar and pestle for 5 minutes affording the product in moderate to excellent yields. The methodology minimises the use of conventional workup and column chromatographic techniques. 相似文献