Radical reactions in pyrolysis of triethylarsine and diethylarsine

Abstract

Pyrolysis of triethylarsine (TEAs) and diethylarsine (DEAsH) has been studied at atmospheric pressure in a flow tube reactor using mass spectrometry. He and D 2 were selected as the carrier gases to determine the ambient effects and to isotopically label the pyrolysis products. For some experiments, supplemental C 2H 5 radicals, produced from pyrolysis of a co-reactant azoethane ((C 2H 5) 2N 2), were added to investigate the role of C 2H 5 in the pyrolysis reactions of the ethylarsines. A significant ambient effect was observed for pyrolysis of TEAs, but not for DEAsH. The pyrolysis of DEAsH was enhanced by adding C 2H 5 radicals while the TEAs pyrolysis was nearly unaffected. DEAsD, rather than DEAsH, was a product for TEAs pyrolysis in D 2; however, the DEAsH pyrolysis produced TEAs in either ambient. This demonstrates that the β-elimination reaction is not a major step. Instead, radical reactions are more likely to dominate the pyrolysis process. Reaction mechanisms for pyrolysis of TEAs and DEAsH in both ambients have been proposed. The rate constants for the reactions involved were determined. In addition, consistency between the proposed reaction pathways and the experimental data has been examined using computer modelling.