An Experimental and Theoretical Study of the Thermal Decomposition of CH Isomers.

The chemistry of small unsaturated hydrocarbons, such as 1,3-butadiene (1,3-CH), 1,2-butadiene (1,2-CH), 2-butyne (2-CH), and 1-butyne (1-CH), is of central importance to the modeling of combustion systems. These species are important intermediates in combustion processes, and yet their high-temperature chemistry remains poorly understood, with various dissociation and isomerization pathways proposed in the literature. Here we investigate the thermal decompositions of 1,3-CH, 1,2-CH, 2-CH, and 1-CH inside a diaphragmless shock tube, at postshock total pressures of 26-261 Torr and temperatures ranging from 1428 to 2354 K, using laser schlieren densitometry.

Observation of a new channel, the production of CH, in the abstraction reaction of OH radicals with acetaldehyde.

Using laser flash photolysis coupled to photo-ionization time-of-flight mass spectrometry (PIMS), methyl radicals (CH) have been detected as primary products from the reaction of OH radicals with acetaldehyde (ethanal, CHCHO) with a yield of ∼15% at 1-2 Torr of helium bath gas. Supporting measurements based on laser induced fluorescence studies of OH recycling in the OH/CHCHO/O system are consistent with the PIMS study. Master equation calculations suggest that the origin of the methyl radicals is from prompt dissociation of chemically activated acetyl products and hence is consistent with previous studies which have shown that abstraction, rather than addition/elimination, is the sole route for the OH + acetaldehyde reaction.