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The reactions of N-methylformamide and N,N-dimethylformamide with OH and their photo-oxidation under atmospheric conditions: Experimental and theoretical studies

Bunkan, A.J.C.; Hetzler, J.; Mikoviny, T.; Wisthaler, A.; Nielsen, C.J.; Olzmann, M.

The reactions of OH radicals with CH3NHCHO (N-methylformamide, MF) and (CH3)2NCHO (N,N-dimethylformamide, DMF) have been studied by experimental and computational methods. Rate coefficients were determined as a function of temperature (T = 260-295 K) and pressure (P = 30-600 mbar) by the flash photolysis/laser-induced fluorescence technique. OH radicals were produced by laser flash photolysis of 2,4-pentanedione or tert-butyl hydroperoxide under pseudo-first order conditions in an excess of the corresponding amide. The rate coefficients obtained show negative temperature dependences that can be parameterized as follows: kOH+MF = (1.3 ± 0.4) × 10-12 exp(3.7 kJ mol-1/(RT)) cm3 s-1 and kOH+DMF = (5.5 ± 1.7) × 10-13 exp(6.6 kJ mol-1/(RT)) cm3 s-1. The rate coefficient kOH+MF shows very weak positive pressure dependence whereas kOH+DMF was found to be independent of pressure. The Arrhenius equations given, within their uncertainty, are valid for the entire pressure range of our experiments. Furthermore, MF and DMF smog-chamber photo-oxidation experiments were monitored by proton-transfer-reaction time-of-flight mass spectrometry. Atmospheric MF photo-oxidation results in 65% CH3NCO (methylisocyanate), 16% (CHO)2NH, and NOx-dependent amounts of CH2NH and CH3NHNO2 as primary products, while DMF photo-oxidation results in around 35% CH3N(CHO)2 as primary product and 65% meta-stable (CH3)2NC(O)OONO2 degrading to NOx-dependent amounts of CH3NCH2 (N-methylmethanimine), (CH3)2NNO (N-nitroso dimethylamine) and (CH3)2NNO2 (N-nitro dimethylamine). ... mehr

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DOI: 10.5445/IR/1000049675
DOI: 10.1039/c4cp05805d
Zitationen: 17
Web of Science
Zitationen: 15
Zugehörige Institution(en) am KIT Institut für Physikalische Chemie (IPC)
Publikationstyp Zeitschriftenaufsatz
Jahr 2015
Sprache Englisch
Identifikator ISSN: 1463-9076
KITopen-ID: 1000049675
Erschienen in Physical Chemistry Chemical Physics
Band 17
Heft 10
Seiten 7046-7059
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