Search results for "Selectivity"
showing 10 items of 1148 documents
Stereocontrolled approach to δ- and γ-lactones and 1,3-diols. The role of X− ion in the selenolactonization
2002
Abstract Two complementary approaches have been realized for the stereoselective synthesis of 4,6-disubstituted δ-lactones and 1,3- anti and syn diols. In the 6- endo selenolactonization the role of the X − ion on the stereoselectivity is shown. Moreover, the highly stereoselective transformation of the 6- endo δ-lactone to the 5- exo γ-lactone is reported.
Identity Formation, Personal Control Over Development, and Well-Being
2006
Individuals' conceptions of their personal goals have been studied in the psychology literature from different perspectives. In this chapter, the processes and implications of one's orientations and self-definitions were analyzed along two dimensions: one's sense of identity, and the self-percepts of autonomous control over development. Several researchers (e.g., Archer, 1989; Brandtstädter & Baltes-Götz, 1990; Pulkkinen & Rönkä, 1994) have concluded, on the basis of literature reviews and empirical findings, that adaptive capacities are associated with a clear sense of identity and personal control over development. Although any given cultural and historical context confines the possible a…
Spectral and temporal distribution of biomolecules by Dynamic SERS
2014
In this thesis, the definition of SERS as a biosensor has been tested and a new approach developed for. Also, in terms of quantification, it has been shown that SERS can be an efficient tool. Concerning the selectivity, the spectral quality was improved. A low limit of detection associated to the statistical and dynamic approach allows a very good sensitivity (under the nanomolar). This approach also enables a high reproducibility in time of the sensor. Thus, as low as SERS does not well answer to the sensor capabilities in a classical approach, in our case the coupling between a non-functionalized GNPs substrate coupled with a microfluidic chip, all mounted on a confocal microscope for tem…
Pesticides: Chemical and Biological.
2013
There is a requirement by World Health Organization (WHO), Food and Agriculture Organization (FAO) and other International Organizations to develop environmentally sustainable systems for controlling pests that are less reliant on chemical pesticides as the primary management tool. However biological control alone cannot at the moment solve all pest problems and must be considered instrument to be used in combination with other methods. Compatibility of chemical pesticides (CP) and biological pesticides (BP) is one of the key for the implementation of Integrated Pest Management (IPM) programs. Testing the compatibility of CP and BP is necessary if these two agents are to be applied together…
Photocatalysis in dimethyl carbonate green solvent: degradation and partial oxidation of phenanthrene on supported TiO2
2014
Dimethyl carbonate (DMC) is here proposed – for the first time – as a green organic solvent for photocatalytic synthesis. In this work, the photocatalytic partial oxidation of phenanthrene in dimethyl carbonate (DMC) by using anatase TiO2 as the photocatalyst is described as paradigmatic example of a green synthetic process starting from polycyclic aromatic hydrocarbons (PAHs). For comparison, the same reaction carried out also in ethanol, 1-propanol or 2-propanol is reported. The use of DMC as the solvent allowed us to achieve 19% and 23% selectivity towards 9-fluorenone and 6H-benzo[c]chromen- 6-one, respectively. The proposed approach may represent both a new green synthetic process and …
Selectivity of hydroxyl radical in the partial oxidation of aromatic compounds in heterogeneous photocatalysis
2007
Abstract The photocatalytic oxidation of different benzene derivatives has been investigated in order to understand how the substituent group affects the selectivity to hydroxylated compounds. Experimental runs were performed by using TiO2 (Merck) aqueous suspensions at natural pH irradiated by near-UV light. The organic molecules used as substrate contained an electron withdrawing group (EWG) (nitrobenzene, cyanobenzene, benzoic acid, 1-phenylethanone), an electron donor one (EDG) (phenol, phenylamine, N-phenylacetamide) or both an EWG and an EDG (4-chlorophenol). The results clearly indicated that the primary photocatalytic oxidation of aromatic compounds containing an EDG gives rise main…
Selective photocatalytic oxidation of 4-substituted aromatic alcohols in water with rutile TiO2 prepared at room temperature
2009
WOS: 000264978500012
Selective oxidation of phenol and benzoic acid in water via home-prepared TiO2 photocatalysts: Distribution of hydroxylation products
2012
Abstract The hydroxylation of phenol (a substrate containing an electron donor group) and of benzoic acid (a substrate containing an electron withdrawing group) has been carried out by the photocatalytic method in aqueous suspensions containing commercial or home prepared TiO2 samples. The aim of the work was to study the distribution of hydroxylation products when different photocatalysts were used and to correlate the selectivity to some physico-chemical features of the powders. The samples were characterized by X-ray diffraction, thermogravimetry, determination of crystalline phase percentage, specific surface area and zero charge point. The photoreactivity results indicate that the prod…
Synthesis of sialyl-Tn antigen. Regioselective sialylation of a galactosamine threonine conjugate unblocked in the carbohydrate portion
1994
Abstract Regioselective and stereocontrolled formation of the sialyl-Tn antigen conjugate 6 was achieved by reacting the NeuNAc-2-xanthate 2 with the GalNAc threonine acceptor 5 bearing three hydroxy groups. Complete deprotection afforded the sialyl-Tn antigen structure 11 .
Efficiency of dihydroxamic and trihydroxamic siderochelates to extract uranium and plutonium from contaminated soils
2021
International audience; Actinide-based mineral phases occurring in contaminated soils can be solubilized by organic chelators excreted by plants, such as citrate. Herein, the efficiency of citrate towards U and Pu extraction is compared to that of siderophores, whose primary function is the acquisition of iron(III) as an essential nutrient and growth factor for many soil microorganisms. To that end, we selected desferrioxamine B (DFB) as an emblematic bacterial trishydroxamic siderophore and a synthetic analog, abbreviated (LCy,Pr)H2, of the tetradentate rhodotorulic acid (RA) produced by yeasts. Firstly, the uranyl speciation with both ligands was assessed in the pH range 2–11 by potentiom…