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Thermal decomposition of methyl 2-azidopropionate studied by UV photoelectron spectroscopy and matrix isolation IR spectroscopy: heterocyclic intermediate vs imine formation

Thermal decomposition of methyl 2-azidopropionate studied by UV photoelectron spectroscopy and matrix isolation IR spectroscopy: heterocyclic intermediate vs imine formation
Thermal decomposition of methyl 2-azidopropionate studied by UV photoelectron spectroscopy and matrix isolation IR spectroscopy: heterocyclic intermediate vs imine formation
Methyl 2-azidopropionate (N3CH3CHCOOCH3, M2AP) has been synthesized and characterized by different spectroscopic methods, and the thermal decomposition of this molecule has been investigated by matrix isolation infrared (IR) spectroscopy and ultraviolet photoelectron spectroscopy (UVPES). Computational methods have been employed in the spectral simulation of both UVPES and matrix IR spectra and in the rationalization of the thermal decomposition results. M2AP presents a HOMO vertical ionization energy (VIE) of 9.60 ± 0.03 eV and contributions from all four lowest-energy conformations of this molecule are detected in the gas phase. Its thermal decomposition starts at ca. 400 °C and is complete at ca. 650 °C, yielding N2, CO, CO2, CH3CN, and CH3OH as the final decomposition products. Methyl formate (MF) and CH4 are also found during the pyrolysis process. Analysis of the potential energy surface of the decomposition of M2AP indicates that M2AP decomposes preferentially into the corresponding imine (M2IP), through a 1,2-H shift synchronous with the N2 elimination (Type 1 mechanism), requiring an activation energy of 160.8 kJ/mol. The imine further decomposes via two competitive routes: one accounting for CO, CH3OH, and CH3CN (?EG3 = 260.2 kJ/mol) and another leading to CO2, CH4, and CH3CN (?EG3 = 268.6 kJ/mol). A heterocyclic intermediate (Type 2 mechanism)—4-Me-5-oxazolidone—can also be formed from M2AP via H transfer from the remote O–CH3 group, together with the N2 elimination (?EG3 = 260.2 kJ/mol). Finally, a third pathway which accounts for the formation of MF through an M2AP isomer is envisioned
1089-5639
8447-8457
Pinto, R.M.
5bd8f4c9-e1df-48ec-b580-de29a1d35ade
Dias, A.A.
221a2ab3-3cc5-4635-b9df-bfce6f767364
Costa, M.L.
1dca80c6-c314-453c-b853-382fbeac2770
Rodrigues, P
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Barros, M.T.
eee3509f-d7a0-4011-bb00-e4f561fda538
Ogden, J.S.
d022e70d-b424-4100-9517-64a46486dd8c
Dyke, J.M.
46393b45-6694-46f3-af20-d7369d26199f
Pinto, R.M.
5bd8f4c9-e1df-48ec-b580-de29a1d35ade
Dias, A.A.
221a2ab3-3cc5-4635-b9df-bfce6f767364
Costa, M.L.
1dca80c6-c314-453c-b853-382fbeac2770
Rodrigues, P
5555d0a7-9223-4961-9164-423712f0e92d
Barros, M.T.
eee3509f-d7a0-4011-bb00-e4f561fda538
Ogden, J.S.
d022e70d-b424-4100-9517-64a46486dd8c
Dyke, J.M.
46393b45-6694-46f3-af20-d7369d26199f

Pinto, R.M., Dias, A.A., Costa, M.L., Rodrigues, P, Barros, M.T., Ogden, J.S. and Dyke, J.M. (2011) Thermal decomposition of methyl 2-azidopropionate studied by UV photoelectron spectroscopy and matrix isolation IR spectroscopy: heterocyclic intermediate vs imine formation. Journal of Physical Chemistry A, 115 (30), 8447-8457. (doi:10.1021/jp2036845). (PMID:21707051)

Record type: Article

Abstract

Methyl 2-azidopropionate (N3CH3CHCOOCH3, M2AP) has been synthesized and characterized by different spectroscopic methods, and the thermal decomposition of this molecule has been investigated by matrix isolation infrared (IR) spectroscopy and ultraviolet photoelectron spectroscopy (UVPES). Computational methods have been employed in the spectral simulation of both UVPES and matrix IR spectra and in the rationalization of the thermal decomposition results. M2AP presents a HOMO vertical ionization energy (VIE) of 9.60 ± 0.03 eV and contributions from all four lowest-energy conformations of this molecule are detected in the gas phase. Its thermal decomposition starts at ca. 400 °C and is complete at ca. 650 °C, yielding N2, CO, CO2, CH3CN, and CH3OH as the final decomposition products. Methyl formate (MF) and CH4 are also found during the pyrolysis process. Analysis of the potential energy surface of the decomposition of M2AP indicates that M2AP decomposes preferentially into the corresponding imine (M2IP), through a 1,2-H shift synchronous with the N2 elimination (Type 1 mechanism), requiring an activation energy of 160.8 kJ/mol. The imine further decomposes via two competitive routes: one accounting for CO, CH3OH, and CH3CN (?EG3 = 260.2 kJ/mol) and another leading to CO2, CH4, and CH3CN (?EG3 = 268.6 kJ/mol). A heterocyclic intermediate (Type 2 mechanism)—4-Me-5-oxazolidone—can also be formed from M2AP via H transfer from the remote O–CH3 group, together with the N2 elimination (?EG3 = 260.2 kJ/mol). Finally, a third pathway which accounts for the formation of MF through an M2AP isomer is envisioned

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Published date: 27 June 2011
Organisations: Chemistry

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Local EPrints ID: 197817
URI: http://eprints.soton.ac.uk/id/eprint/197817
ISSN: 1089-5639
PURE UUID: 39a61d5c-254c-4716-98ec-2dafe572a9b8
ORCID for J.M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X

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Date deposited: 28 Sep 2011 08:17
Last modified: 03 Dec 2019 02:07

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Contributors

Author: R.M. Pinto
Author: A.A. Dias
Author: M.L. Costa
Author: P Rodrigues
Author: M.T. Barros
Author: J.S. Ogden
Author: J.M. Dyke ORCID iD

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