Alkoxy Isothiocyanates as Intermediates in the Flash Vacuum Pyrolysis of Alkoxythioureas

Carl Th. Pedersen; Frank Jensen; Robert Flammang

doi:10.1071/CH08406

RESEARCH ARTICLE

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Alkoxy Isothiocyanates as Intermediates in the Flash Vacuum Pyrolysis of Alkoxythioureas

Carl Th. Pedersen ^A ^D , Frank Jensen ^B and Robert Flammang ^C

+ Author Affiliations

- Author Affiliations

^A Department of Physics and Chemistry, University of Southern Denmark – Odense, DK-5230 Odense M, Denmark.

^B Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark.

^C Department of Chemistry, University of Mons-Hainaut, B-7000 Mons, Belgium.

^D Corresponding author. Email: cthp@ifk.sdu.dk

Australian Journal of Chemistry 62(1) 69-74 https://doi.org/10.1071/CH08406
Submitted: 25 September 2008 Accepted: 21 November 2008 Published: 21 January 2009

Abstract

Methoxy isothiocyanate MeO–NCS 2b was detected by matrix isolation IR spectroscopy following flash vacuum pyrolysis (FVP) of N-methoxythioureas, N-tert-butyl-N′-methoxythiourea 1d being the best precursor. Isothiocyanates 3, amines, and aldehydes are also generated by FVP of several substituted N-alkoxythioureas 1 in the temperature range 400–800°C. The formation of these products can be explained either by secondary pyrolysis of initially formed alkoxy isothiocyanates 2, or by an initial cleavage of the O–N bond in 1 via a free-radical mechanism. N-Cyanoamines 4 and/or the tautomeric carbodiimides 5 are formed by another pathway. The pyrolyses were monitored by IR spectroscopy and online mass spectrometry or tandem mass spectrometry, and the reaction mechanisms are supported by theoretical calculations.

Acknowledgements

The authors thank Professor Curt Wentrup, the University of Queensland, Australia, for valuable discussions and suggestions. The support of the Danish National Science Research Council and the Danish Centre for Scientific Computing is acknowledged. The Mons Laboratory thanks the Fond National de la Research Scientifique for its contribution towards purchase of the Micromass AutoSpec 6F mass spectrometer.

References

Alkoxy Isothiocyanates as Intermediates in the Flash Vacuum Pyrolysis of Alkoxythioureas

Abstract

Acknowledgements

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