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The University of Southampton
Chemistry

Research project: Dyke: Use of High Temperature Photoelectron Spectroscopy to study the decomposition of Organic Azides and other High Energy Density Materials

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It is well known that azides release nitrogen very easily when heated. liberating a large amount of energy.

They have a number of practical applications because of this characteristic, notably in the manufacture of explosives, silicon nitride semiconductors, and photoresistors. They are also a source of gas for air bags in vehicles and have biomedical applications. Recent studies that we have performed on the thermal decomposition of some organic azides by photoelectron (PE) spectroscopy and infrared matrix isolation spectroscopy have shown that two distinct decomposition pathways must be invoked to account for the experimental observations. The first pathway, called Type 1, is characterised by the initial liberation of nitrogen and the formation of an imine. This mechanism has been invoked to account for some of the products of azidoethanol and azidoacetone decompositions. A second mechanism, which has been termed Type 2, involves transfer of a proton or more generally an alkyl group onto the electron deficient N atom from a more remote site in the molecule and may be envisaged as involving a cyclic transition state. This mechanism was first recognised in studies of the decomposition of azidoacetic acid and ethylazidoacetate.

It is proposed to study the mechanisms of decomposition of a number of selected organic azides, notably azidoacetates, azidoamides, azidoformates and azidonitriles, with the overall aim of understanding the mechanisms of their decompositions and of characterising the reaction intermediates involved.

Related studies will also be made on the thermal decomposition of some recently prepared alkali and alkaline earth metal crown-ether azide complexes.

The main experimental methods used to study these decompositions are matrix isolation infrared spectroscopy and high temperature photoelectron spectroscopy.

Two PE spectrometers will be used in these studies; one using resistive heating (to achieve temperatures up to 1500 K) and the other using radiofrequency induction heating (to achieve temperatures up to 2500 K). Interpretation of the experimental results is assisted by results of electronic structure calculations which are used to compute the relevant parts of the potential energy surfaces, as well as PE and infrared spectra of the parent azides, and the intermediates and products obtained on thermal decomposition.

Related research groups

Computational Systems Chemistry
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