AUTOOXYDATION OF AMINES: ON INVESTIGATION OF THE MECHANISM OF THE BASE-CATALYZED OXIDATION OF AMINES IN AQUAEOUS SOLUTION WITH MOLECULAR OXYGEN

Información del proyecto

Identificador del acuerdo de subvención: SC1*0030

Proyecto cerrado

Fecha de inicio 1 Febrero 1989

Fecha de finalización 31 Enero 1992

Financiado con arreglo a

• Programme plan (EEC) to stimulate the international cooperation and interchange needed by European research scientists (SCIENCE), 1988-1992

Coste total

Sin datos

Aportación de la UE

Sin datos

Coordinado por

UNIVERSITY OF BOLOGNA
Italy

Objetivo

The reaction mechanism of the autoxidation and dealkylation reaction of tertiary alkyl amines induced by base in aqueous solution in the presence of molecular oxygen has been studied. Electron paramagnetic resonance (EPR) experiments were carried out to provide direct evidence for the mechanism involved in the dealkylation and oxidation process and the conditions leading to the dealkylation were explored. It was found that the pH has to be greater than, or equal to, 8 for the process to occur. It was proved that molecular oxygen (normally from the atmosphere) is involved. The presence of a beta-methylene group on one of the alkyl chains was found to be a requirement. A qualitative measurement of the rate of reaction was performed by a stop flow experiment and it was shown that the EPR signal reaches its own maximum intensity after a few seconds. Experimental results suggest that the electron withdrawing or donating effect in the beta-substituents is very crucial. Experiments using spin trapping and labelling were inconclusive as were attempts to show the presence of superoxide dismutase. Product studies were carried out and the results suggest that radical decomposition is a very minor pathway.

It is concluded that the mechanism for nitroxide formation probably involves electron transfer from the unprotonated amine to oxygen, to give 2 charged species stabilized in the aqueous environment. It is unlikely that the reaction mechanism involves the prior formation of nitroxides or protonated amines even though these species undergo subsequent attack. Given that a relatively slow, minor reaction of the intermediate radical cation may be involved, 2 potential mechanisms may be suggested to account for most of the observations: reaction with base
It is proposed to determine the mechanism, and the controlling structural and electronic features, of the rapid autooxidation of certain tertiary amines under mild conditions (in oxygenated aqueous solution at pH ca. 10.). The approach will involve both a study of the kinetics and products of reaction of a variety of substrates, as well as a spectroscopic investigation of short-lived intermediates (radicals, anions, peroxy species) with e.s.r. (flow, photolysis, and
spin-trapping).

Ámbito científico (EuroSciVoc)

• ciencias naturales › ciencias químicas › electroquímica › electrólisis
• ciencias naturales › ciencias químicas › química orgánica › aminas

Programa(s)

• FP2-SCIENCE - Programme plan (EEC) to stimulate the international cooperation and interchange needed by European research scientists (SCIENCE), 1988-1992

Tema(s)

Datos no disponibles

Convocatoria de propuestas

Datos no disponibles

Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

UNIVERSITY OF BOLOGNA

• Aportación de la UE: Sin datos
• Dirección: Viale Risorgimento 4 ; 40136 BOLOGNA ; Italia
• Coste total: Sin datos

Participantes (1)

University of York

Reino Unido

• Aportación de la UE: Sin datos
• Dirección: Heslington - ; YO1 5DD York
• Coste total: Sin datos