Mechanisms of the thermal decay of chlorpropham

Smith, M.J. , Müller, S., Sander, W. and Bucher, G. (2013) Mechanisms of the thermal decay of chlorpropham. Journal of Hazardous Materials, 246-47, pp. 154-162. (doi: 10.1016/j.jhazmat.2012.12.003)

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DFT calculations were performed on the thermal reactions of chlorpropham 1, a carbamate pesticide and plant growth regulator frequently used in the storage of potatoes. At the conditions normally used in applying 1 (injection of a methanolic solution of 1 into a hot air stream, T ∼ 500 °C), both ester pyrolysis of 1 and a methanol-or water-catalysed isocyanate cleavage are expected to proceed rapidly (lifetime of 1 less than a second). In both reactions, the final reaction product will be toxic and carcinogenic m-chloroaniline 2. Matrix-isolation experiments indicate that 1 undergoes thermal decay at temperatures as low as 250 °C. Up to temperatures of ca. 500 °C, formation of m-chlorophenylisocyanate 4 and isopropanol was the predominant reaction observed, while formation of propene, CO2, and m-chloroaniline 2 was the most important reaction channel at higher pyrolysis temperatures. m-Chlorophenyl carbamic acid 3 could not be observed. The results indicate that at lower temperatures, 1 decays exclusively via isocyanate cleavage of 1, provided that traces of catalytic water or other protic compounds are present. At higher temperatures, ester cleavage of 1 becomes competitive and outweighs the isocyanate cleavage by a factor of ca. 10:1.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Bucher, Dr Goetz and Smith, Dr Margaret
Authors: Smith, M.J., Müller, S., Sander, W., and Bucher, G.
College/School:College of Arts > School of Culture and Creative Arts > History of Art
College of Science and Engineering > School of Chemistry
Journal Name:Journal of Hazardous Materials

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