G. Casalbore

Anodic chlorination of aromatic compounds in acetic acid

Summary The electrochemical chlorination of some aromatic compounds at the oxidation potential of Cl − ion has been studied by several electrochemical techniques in anhydrous acetic acid. The species Cl − 2 was evidentiated to be the chlorinating agent under the experimental conditions considered.

Anodic bromination of aromatic compounds in anhydrous acetic acid: Toluene and p-xylene

Summary The mechanism of electrochemical bromination of aromatic compounds in anhydrous acetic acid has been investigated. Bromine ion gives two waves in anhydrous acetic acid, by addition of p -xylene or toluene. At the first wave Br 2 is formed which gives rise to an oxidizable complex with the aromatic substrate. At the potential of the first wave this oxidizable complex always yields the aromatic ring substituted bromo derivative and monobromoacetic acid. At the second wave the aromatic substrate oxidation occurs depolarized by Br − , and probably via the same oxidizable complex that is formed at the first wave. The formation of aromatic ring-substituted bromo derivative and monobromoacetic acid takes place.

Anodic oxidation of halides in anhydrous acetic acid

Summary The electrochemical behaviour of chloride and bromide ion in anhydrous acetic acid on a platinum electrode has been studied. The most probable reaction path for the oxidation of the halides seems to be: 3 X − → X 3 − + 2 e X − − → X 2 + X −

Electrochemical bromination of benzene, toluene and xylene in acetonitrile

A method for the preparation of bromo derivative compounds of aromatics is proposed and the electrodic process involved in the bromination on the third wave of the system Br−/aromatic substrate in acetonitrile is discussed.

[Ru(bpy)3]2+-trivalent titanium. A photochemical system with hydrogen production from aqueous solutions by visible light

Abstract Molecular hydrogen, detected by gas-chromatographic and mass-spectrometric measurements, was obtained by irradiating with visible light aqueous hydrochloridic solutions of [Ru(bpy) 3 ] 2+ and trivalent titanium. The active species is the 3 CT of [Ru(bpy) 3 ] 2+ , which is quenched by Ti(III). The suggested mechanism is an electron transfer with Ti(II) formation. The back reaction between [Ru(bpy) 3 ] 3+ and Ti(II) is hindered by the very fast competitive reaction of Ti(II) (not stable in acid aqueous solutions) with H + , carrying to hydrogen evolution.

Electrodic oxidation of Cl− ion on smooth platinum electrode in nitromethane

Summary The electrochemical oxidation of Cl− ion in nitromethane on a smooth platinum electrode has been investigated. The experimental results of the coulometric measurements are fitted satisfactorily by current-charge curves obtained theoretically for the following mechanism: 3 C 1 − → C 1 3 − + e C 1 3 − → slow C 1 2 + C 1 −

Charge-transfer complexes betweenp-toluidine and iodine in solution: A spectrophotometric and voltammetric study

The charge-transfer interaction between an aromatic amine (p-toluidine) and a halogen (iodine) is investigated in different solvents. The effects of the solvent dielectric constant, of the ionic strength and of the light absorbed on the transformation of the intermediate “outer” complex into a polar “inner” structure are studied. An overall reaction mechanism is suggested.

Anodic chlorination of aromatic compounds in acetic acid part II

Abstract The anodic chlorination of aromatic compounds in anhydrous acetic acid has been further investigated. Evidence has been found for two different methods of electrochemical chlorination, in the systems Cl2/aromatic compounds and Cl−/aromatic compounds. These methods were also compared with the uncatalyzed chemical chlorination reaction. The yields of monochlorinated products and the related isometric distributions were taken into account. Since the isomeric distributions are equal with chemical and electrochemical chlorination methods, the formation of the same intermediate was proposed for both.

Charge-transfer complexes betweenp-toluidine and iodine in solution: A kinetic study

The kinetics of charge-transfer interaction betweenp-toluidine and iodine in methylene chloride was investigated in depth. Thethermal process of formation of the“inner” complex was found to proceed to an equilibrium. Thephotochemical process follows a different reaction coordinate, going through the formation of an exciplex between the excited“outer” complex and the amine ground state. In both cases the same ionic complex (Am2I+I3−, whereAm stands forp-toluidine) was detected as the final product.ZusammenfassungDie Kinetik der Charge-Transfer-Wechselwirkung zwischenp-Toluidin und Jod in Methylenchlorid wurde ausführlich untersucht. Derthermische Prozeß, der zur Bildung des„inner“-Komplexes führt, geht bis zu einem Gleichgewicht. Derphotochemische Prozeß folgt einer unterschiedlichen Reaktionskoordinate und verläuft über die Bildung eines Exziplexes zwischen dem angeregten„outer“-Komplex und dem Amin im Grundzustand. In beiden Fällen wurde derselbe ionische Komplex (Am2I+I3−, wobeiAm fürp-Toluidin steht) als Endprodukt festgestellt.

Photochemical behaviour of Ru(bpy)3Cl2 complex in strong acidic media

Abstract Room temperature deaerated solutions containing the Ru(bpy) 3 Cl 2 complex are not stable when irradiated for long periods with λ > 400 nm. The decomposition rate increases with decreasing pH of the solution. The pH dependence of the photochemical and photophysical behaviour suggests an association between Ru(bpy) 3 Cl 2 and H + both in the ground and in the excited state of the complex.