163 research outputs found
Photochemistry of triphenylamine (TPA) in homogeneous solution and the role of transient N-phenyl-4a,4b-dihydrocarbazole. A steady-state and time-resolved investigation
No full textThe photoreactivity of triphenylamine in homogeneous media has been investigated by means of laser flash photolysis spectroscopy and preparative experiments. The goal of this study consists in the evaluation of the photophysical and photochemical behavior of transient N-phenyl-4a,4b-dihydrocarbazole (DHC0) under polar and non-polar solvents which was not performed yet. The kinetic parameters of such a key intermediate including lifetime (tau(d), tau(R) and tau(ox)) and rate constants (k(d), k(R) and k(ox)) have been measured and the intermediacy of DHC0 in the co-oxidation of nucleophilic substrates such as sulfides and phosphines was investigated by a combined time-resolved and steady-state approach. Two distinctly oxidizing intermediates, a hydroperoxy radical and a hydroperoxide derivative were formed from transient DHC0 in the presence of molecular oxygen. Radical I oxidizes triarylphosphines, whereas intermediate II converts sulfides into the corresponding sulfoxides
Effect of Sustainable and Confined Media on the Photoinduced [6π]-Electrocyclization Reaction of Diphenyl and N-Methyldiphenylamines
No full textA systematic investigation of the photoinduced [6π]-electrocyclization reaction of diphenylamine and N-methyldiphenylamine has been carried out under steady-state and time-resolved conditions in homogeneous (cyclohexane, acetonitrile and methanol) and micellar solutions (sodium dodecyl sulfate -SDS, cetyltrimethylammonium chloride-CTAC and polyethylene glycol monododecyl ether-Brij P35). The photolysis of such compounds in both homogeneous and micro-heterogeneous media afforded the corresponding carbazoles in almost quantitative yield under oxidative conditions. Furthermore, the relative rate of formation of the photoproducts increases when moving from homogeneous media to micellar solution, due to the environmental confined and hydrophobic micellar core as highlighted by 1D and 2D NMR (NOESY and DOSY) spectroscopic analyses
Primi dati di distribuzione del visone americano (Neovison vison) nella provincia di Vicenza. First data on the distribution of the American mink in the Province of Vicenza
No full textNatura Vicentin
Photochemical Co-Oxidation of Sulfides and Phosphines with Tris(<i>p</i>‑bromophenyl)amine. A Mechanistic Study
No full textThe
photochemistry of tris(p-bromophenyl)amine
was investigated in a nitrogen- and oxygen-flushed solution under
laser flash photolysis conditions. The detected intermediates were
the corresponding amine radical cation (“Magic Blue”)
and the N-phenyl-4a,4b-dihydrocarbazole radical cation
that, under an oxygen atmosphere, is converted to the corresponding
hydroperoxyl radical. The role of the last species was supported by
the smooth co-oxidation of sulfides to sulfoxides. On the other hand,
co-oxidation of nucleophilic triarylphosphines to triarylphosphine
oxides arose from an electron transfer between the photogenerated
“Magic Blue” and phosphine that prevented the amine
cyclization. In this case, intermediate Ar3POO•+ was found to play a key role in phosphine oxide formation
Selectivity in the photo-fries rearrangement of some aryl benzoates in green and sustainable media. Preparative and mechanistic studies
No full textIrradiation of a series of p-substituted aryl benzoates under N2 atmosphere in homogeneous and micellar media was investigated by means of steady-state condition and of time-resolved spectroscopy. A notable selectivity in favor of the 2-hydroxybenzophenone derivatives was observed in micellar media. The benzophenone derivatives were the main photoproduct. On the other hand, in homogeneous media (cyclohexane, acetonitrile, and methanol) the observed product distribution was entirely different, viz. substituted 2-hydroxybenzophenones, p-substituted phenols, benzyl and benzoic acid were found. The binding constants in the surfactant were also measured and NOESY experiments showed that the aryl benzoates were located in the hydrophobic core of the micelle. Laser flash photolysis experiments led to the characterization of both p-substituted phenoxy radical and substituted 2-benzoylcyclohexadienone transients in homogeneous and micellar environment
Photoinduced One-Electron Oxidation of Estrone Derivatives: A Combined Steady-State and Time-Resolved Spectroscopy Investigation
No full textA detailed investigation of the photophysics and of the redox properties of a set of selected estrone carboxylate and sulfonate esters was carried out by means of steady-state and time-resolved spectroscopies. The observed dual fluorescence was assigned to an efficient intramolecular energy transfer from the aromatic moiety to the carbonyl group. On the other hand, the photoinduced monoelectronic oxidation of R−OX in the presence of persulphate anion is followed by mesolytic fragmentation of the so generated radical cation into the corresponding phenoxyl radical with rate constant values (kfrag) of 104–105 s−1, that depend on the X−O bond dissociation energy values
Ruta chalepensis L. (Rutaceae) leaf extract: chemical composition, antioxidant and hypoglicaemic activities
No full textRuta chalepensis L. (Rutaceae) leaf extract was investigated for its chemical profile and antioxidant and hypoglycaemic properties. The antioxidant effects were investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), Chi-carotene bleaching, and metal chelating activity assays. The carbohydrate-hydrolysing enzymes inhibition assay was used to test the hypoglycaemic potential. R. chalepensis showed a high content of hesperidin and rutin with values of 591.9 and 266.7 mg/g dry extract, respectively. The extract exhibited a promising protection of lipid peroxidation (IC50 value of 16.9 mu g/mL) and inhibited both alpha-amylase and alpha-glucosidase enzymes in a concentration-dependent manner. The highest activity was found against alpha-amylase (IC50 value of 69.0 mu g/mL). The obtained results support the use of R. chalepensis leaves as healthy food ingredients
Decreased small mammals species diversity and increased population abundance along a gradient of agricultural intensification
No full textAgricultural intensification has been widespread worldwide over the last decades and has lead to a loss of semi-natural habitats. These changes are likely to have affected both the composition and diversity of small mammal communities living in agricultural landscapes. In this context, we compared population abundance (expressed as an index of relative abundance), species richness (S), and species diversity (expressed as Shannon and Pielou indexes) of small mammal assemblages (i.e. sub-sets of the entire small mammal community) living in three areas in North-East Italy positioned along a gradient of agricultural land-use intensification (measured with the Landscape Conservation Index). We expected that assemblages would be less diverse and dominated by generalist species where the landscape was more intensely cultivated and where semi-natural habitats were less common. In the three areas, from a total of 4630 trap-nights, 668 individuals were captured with Sherman traps, belonging to four species (Apodemus agrarius, A. flavicollis, A. sylvaticus and Microtus arvalis). The results showed that population abundance, type of species present (but not species richness), and species diversity were affected by agricultural intensification and landscape naturalness. In particular, moving from less natural to more natural landscapes, we observed no effect on richness of species but increasing diversity due to a greater abundance of the more specialist species, such as A. agrarius and, partially, A. flavicollis, the latter only present in the most natural area. Generalist species, namely A. sylvaticus, and those associated with disturbed environments, such as M. arvalis, were instead more abundant in less natural landscapes. When considering population abundance, the highest overall abundance of small mammals was found in the most disturbed landscape. The results were consistent with those of research carried out in other agroecosystems of Europe and highlight the controversial effect of the anthropogenic impact on small mammal assemblages, since a decrease in species diversity may be associated with an increased overall population abundance, due to the success of few generalist species. © 2014 Associazione Teriologica Italiana
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