Kinetics and mechanism of the thermal decomposition of unsaturated aldehydes: benzaldehyde, 2-butenal, and 2-furaldehyde

The thermal unimolecular decompositions of benzaldehyde (BA), crotonaldehyde (CA), and furfural (FA) have been investigated in a flow reactor at very low pressures by modulated beam mass spectrometry above 1040 K. Each reaction proceeds by a different mechanism. Whereas BA decomposes by C(O)-H bond fission CA readily undergoes decarbonylation to propene via a three-center transition-state reaction. FA decomposition into vinylketene and CO involves ring opening followed by H-atom transfer in the resulting biradical. Overall high-pressure Arrhenius parameters for the three reactions are derived from kinetic data.