Schindler , R. N., Dethlefs , J. and Schmidt, Mark (1996) Some Results on the Mechanism of the Reaction between O(3P)-Atoms and HOCl. An Experimental and Ab Initio Model Study. Berichte der Bunsengesellschaft für Physikalische Chemie, 100 . pp. 1242-1249. DOI 10.1002/bbpc.19961000723.

Abstract

The rate constant for the title reaction was redetermined using discharge flow technique and mass spectrometric measurements of HOCl consumption. The overall rate constant k = (1.7±0.3)×10−13 cm3 molecule−1 s−1 was obtained and found to be practically independent of temperature in the range 213 K≤T≤298 K. In experiments using 18O atoms the time dependence in the formation of the products 18O16O, HC1 and Cl2 was determined. Based on the experimental data available it is proposed that the reaction occurs via an intermediate complex mechanism but it could not be decided by which primary steps the reaction is initiated.

Ab initio model calculations were carried out in an attempt to quantify conceived reaction pathways. Structures and energetics of the intermediates were computed. On the basis of these calculations it is suggested that Cl abstraction from HOC1 should be regarded as the preferred initiation step. The O‐atom attack leads to the formation of an intermediate HOClO. Alternative reaction pathways, like H abstraction from HOCl by O‐atom attack, or a mechanism in which HO2 and Cl are formed were found to be less probable. In the present calculations no support could be found for the thermodynamically most preferred reaction route to contribute to product formation. Structure and energy of the intermediate HOC1O are computed.

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