Thermal decomposition products of butyraldehyde

摘要

The thermal decomposition of gas-phase butyraldehyde, CH_3CH_2CH_2CHO, was studied in the 1300-1600 K range with a hyperthermal nozzle. Products were identified via matrix-isolation Fourier transform infrared spectroscopy and photoionization mass spectrometry in separate experiments. There are at least six major initial reactions contributing to the decomposition of butyraldehyde: a radical decomposition channel leading to propyl radical + CO + H; molecular elimination to form H_2 + ethylketene; a keto-enol tautomerism followed by elimination of H_2O producing 1-butyne; an intramolecular hydrogen shift and elimination producing vinyl alcohol and ethylene, a β-C-C bond scission yielding ethyl and vinoxy radicals; and a γ -C-C bond scission yielding methyl and CH_2CH_2CHO radicals. The first three reactions are analogous to those observed in the thermal decomposition of acetaldehyde, but the latter three reactions are made possible by the longer alkyl chain structure of butyraldehyde. The products identified following thermal decomposition of butyraldehyde are CO, HCO, CH_3CH_2CH_2, CH_3 CH_2CH=C=O, H_2O, CH_3CH_2C≡CH, CH_2CH_2, CH_2=CHOH, CH_2CHO, CH_3, HC≡CH, CH_2CCH, CH_3C≡CH, CH_3CH=CH_2, H_2C=C=O, CH_3CH_2CH_3, CH_2 =CHCHO, C_4H_2, C_4H_4, and C_4H_8. The first ten products listed are direct products of the six reactions listed above. The remaining products can be attributed to further decomposition reactions or bimolecular reactions in the nozzle.