A convenient and simple method for the preparation of diphenylpropane-1,2-diones is described. The process involves rearrangement of α-epoxyketones on silica gel; an unusual migration of a proton instead of the more common benzoyl migration. 相似文献
Various ketones were efficiently transformed into the corresponding amines using ammonium formate in the presence of Zn dust or 10% Pd/C. The low-cost Zn dust method proved to be effective in amine formation from carbonyl groups at the benzylic side-chain position of aromatic systems, whereas 10% Pd/C was an efficient catalyst in the reductive aminations of carbonyl groups non-conjugated with any π-system. The 10% Pd/C-catalyzed reductions were performed more effectively in a continuous-flow X-Cube reactor than in the batch system. 相似文献
In this paper the results of an inter-comparison employing three distinct techniques for measuring indoor radon activities are discussed: (i) NRPB–SSI dosimeter, a diffusion chamber, CR-39 based, calibrated in a controlled radon chamber; (ii) a diffusion chamber, CR-39 based, calibrated via nuclear emulsion; (iii) canister with activated charcoal. Totally 39 dwellings of Poços de Caldas city (Minas Gerais State, Brazil), located in a high natural radioactivity region, have been monitored during a six months period.
Dosimeters (i) and (ii) were exposed continuously in all of 39 dwellings and dosimeter (iii) was exposed in 10 of them, randomly chosen. In this case the individual exposures lasted around 5 days and 4 equally time spaced exposures were made in each dwelling. Results produced by techniques (i) and (ii) show a great level of concordance. Individual results of technique (iii) for each residence show great fluctuations, but their mean results statistically agree with the other techniques. So our results indicate that active charcoal technique can be used to study average term radon variation (in few days), but its individual results cannot reflect long-term indoor radon activity. 相似文献
Comparative investigations of new regenerated cellulosic fibers, bamboo viscose fiber and Tencel, together with conventional
viscose fibers have been carried out to explain the similarity and difference in their molecular and fine structure. The analyses
jointly using SEM, XRD and IR reveal that all the three fibers belong to cellulose II. Tencel consists of longer molecules
and has a greater degree of crystallinity, while bamboo viscose fiber has a lower degree of crystallinty. TG-DTG-DSC study
shows three fibers resemble in thermal behavior with a two-step decomposition mode. The first step is associated to water
desorption, suggesting that bamboo viscose fiber holds better water retention and release ability, the second a depolymerization
and decomposition of regenerated cellulose, indicating that Tencel is more thermally stable in this process than bamboo and
conventional viscose fiber. 相似文献