Giovanni V. Sebastiani

TiO2-catalyzed photooxygenation of methylaromatic compounds in the presence of Ag2SO4 in CH3CN

Methylaromatic compounds have been photooxygenated in CH3CN, at room temperature, in the presence of TiO2 and Ag2SO4, to form benzaldehydes and, in some cases, benzoic acids, in yields up to 50%

Photochemical oxidation and autoxidation of some cycloalkanes promoted by ceric ammonium nitrate in acetonitrile

Abstract The oxidation and autoxidation of adamantane, norbornane and cyclohexane can be photochemically promoted by ceric ammonium nitrate in acetonitrile at room temperature, both processes being extremely efficient and selective with adamantane.

The photoelectrochemical oxidation of benzyl derivatives at Ti/TiO2 anodes. A mechanistic approach through current efficiency and density measurementst

The mechanism of the photoelectrochemical sensitised oxidation of 4- and 3-methoxybenzyl alcohols and silanes at Ti/TiO2 ‘anatase’ and ‘rutile’ photoanodes has been investigated through current efficiency and density measurements.

Dark adsorption equilibrium constants of benzylic derivatives on TiO2 and their implications in the sensitised heterogeneous photooxidation

The “dark” adsorption equilibrium constants of different series of benzylic derivatives on TiO2 suspended in CH3CN were determined through a Langmuir-type adsorption isotherm. In particular, the similarity of the K values of differently ring substituted α-OH derivatives within the same series confirms the previously suggested preferential adsorption of the hydroxyl group (at the oxygen atom) with respect to the aromatic moiety.

Photooxidation of Benzyl Alcohols Sensitized by TiO2 in CH3CN in the Presence of Ag2SO4. Kinetic Evidence for the Involvement of Adsorption Phenomena

X-Ring substituted benzyl alcohols are photooxidized to the corresponding aldehydes by TiO2 in CH3CN in the presence of Ag2SO4 and kinetic evidence suggests a changeover of the electron abstraction site from the aromatic moiety (X=4-CH3O, 4-CH3, 4-Cl, H, 3-Cl) to the hydroxylic group (X=3-CF3, 4-CF3), probably owing to the preferential adsorption of OH on TiO2.

Titanium dioxide photocatalysed oxidation of benzyltrimethylsilanes in the presence of silver sulfate

In the presence of Ag2SO4, the TiO2-mediated photochemical oxidation of substituted benzyltrimethylsilanes in acetonitrile leads to diarylethanes (50–74%) with a significant intermolecular selectivity (ρ=–2.5).

Kinetic study of the base-induced anti and syn eliminations from 2,3-dihalogeno-2,3-dihydrobenzofurans in different base-solvent systems

dibromo-5-chloro-2,3-dihydrobenzofuran and anti eliminations from cis- 2,3-dichloro-2,3-dihydrobenzofuran have been investigated in different base-solvent systems. Anti elimination is favored over the syn by a factor of -33 000 in EtONa-EtOH, -10 000 in t-BuOK-t-BuOH, and >10 000 in t-BuOK-t-BuOH, in the presence of 18-crown-6 ether. The rate of both the anti and syn pathway increases with increasing the medium basicity, the syn path being also favored, however to much less extent, by base association. From the values of the deuterium kinetic isotope effect and substituent effect it can be concluded that the transition state structure for the syn elimination from trans2,3-dibromo-2,3-dihydrobenzofuran is significantly affected by base association, but not by medium basicity. trans-2,3-Dihalogeno-2,3-dihydrobenzofurans are very suitable substrates for the study of elimination processes owing to their tendency to be converted by bases into the aromatic benzofuran system. Recently we have investigated the reactions of trans-2,3-dibromo-2,3-dihydrobenzofuran (I) with bromide and chloride ions in dipolar aprotic so1vents.l With bromide ions I is dehalogenated to benzofuran, whereas with chloride ions it gives mainly trans- 2,3-dichloro-2,3dihydrobenzofuran (11)2 together with ca. 10% of 3-bromobenzofuran presumably formed in a syn dehydrobromination process. Syn dehydrohalogenation, however, is the only reaction observed when I or I1 reacts with an alkoxide in the corresponding alcohol. Owing to the increasing importance of syn elimination reactions, it seemed interesting to carry out a detailed kinetic investigation, including the determination of deuterium kinetic isotope effect and substituent effect of the reactions of I and I1 in different alkali alkoxide-alcohol systems. For comparison purposes some anti eliminations from cis -2,3dichloro-2,3-dihydrobenzofuran (111) have also been studied.3 Results and Discussion The eliminations from 1-111, trans-2,3-dibromo-3-deuterio-2,3-dihydrobenzofuran (IV), and trans-2,3-dibromo5-chloro-2,3-dihydrobenzofuran (V) have been studied in EtOK-EtOH, n-BuOK-n-BuOH, t-BuOK-t-BuOH, nRuOK-18C6-n-BuOH (18C6 is 18-crown-6 ether), and t BuOK-18C6-t-BuOH. Some experiments for the reactions of 1-111 in EtONa-EtOH have been also carried out. In each

Deuteriodeprotonation of some heteroaromatic bicyclic compounds

Rate constants for deuteriodeprotonation in D2SO4 at the 2- and 3-positions of the four isomeric thieno[2,3-b]-, thieno[2,3-c]-, thieno[3,2-b]-, and thieno[3,2-c]-pyridines and of furo[3,2-b]- and seleno[3,2-b]-pyridine have been determined. The slopes of the rate profiles give evidence that all the substrates undergo exchange as protonated species. The relative reactivities are given as standard rates and discussed in terms of electronic effects in heteroaromatic systems.

Photocatalytic Activity in CN Related to the Surface Properties of Powders Prepared by Sol-Gel Method

Some powders, prepared from titanium(IV)tetraisopropoxide by the sol-gel method and thermally treated between 100 and C, have been characterized by X-ray powder diffraction and by nitrogen adsorption and desorption at 77 K to calculate the BET-specific surface area, from which the micropore volume and the external surface area can be derived. The photocatalytic activity () of the above powders has been evaluated considering the -sensitized photo-oxidation of 4-methoxybenzyl alcohol in CN as the test reaction. The decrease of have been related to the decrease of the BET surface area, the micropore volume, and the external surface area of the powders, but a satisfactory linear correlation is observed only for the last superficial parameter.

Exploring the relationship between the magnitudes of seismic events

The distribution of the magnitudes of seismic events is generally assumed to be independent on past seismicity. However, by considering events in causal relation, for example, mother-daughter, it seems natural to assume that the magnitude of a daughter event is conditionally dependent on one of the corresponding mother events. In order to find experimental evidence supporting this hypothesis, we analyze different catalogs, both real and simulated, in two different ways. From each catalog, we obtain the law of the magnitude of the triggered events by kernel density. The results obtained show that the distribution density of the magnitude of the triggered events varies with the magnitude of their corresponding mother events. As the intuition suggests, an increase of the magnitude of the mother events induces an increase of the probability of having “high” values of the magnitude of the triggered events. In addition, we see a statistically significant increasing linear dependence of the magnitude means.