The pyrolysis products of gas-phase 3-oxetanone were identified via matrix-isolation Fourier transform infrared spectroscopy and photoionization mass spectrometry. Pyrolysis was conducted in a hyperthermal nozzle at temperatures from 100 to 1200 °C with the dissociation onset observed at ∼600 °C. The ring strain in the cyclic structure of 3-oxetanone causes the molecule to decompose at relatively low temperatures. Previously, only one dissociation channel, producing formaldehyde and ketene, was considered as significant in photolysis. This study presents the first experimental measurements of the thermal decomposition of 3-oxetanone demonstrating an additional dissociation channel that forms ethylene oxide and carbon monoxide. Major products include formaldehyde, ketene, carbon monoxide, ethylene oxide, ethylene, and methyl radical. The first four products stem from initial decomposition of 3-oxetanone, while the additional products, ethylene and methyl radical, are believed to be due to further reactions involving ethylene oxide.

The thermal decomposition of gas-phase butyraldehyde, CH3CH2CH2CHO, 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 H2 + ethylketene; a keto-enol tautomerism followed by elimination of H2O 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 CH2CH2CHO 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, CH3CH2CH2, CH3CH2CH=C=O, H2O, CH3CH2C≡CH, CH2CH2, CH2=CHOH, CH2CHO, CH3, HC≡CH, CH2CCH, CH3C≡CH, CH3CH=CH2, H2C=C=O, CH3CH2CH3, CH2=CHCHO, C4H2, C4H4, and C4H8. 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.

A hyperthermal nozzle was utilized to study the thermal decomposition of propionaldehyde, CH3CH2CHO, over a temperature range of 1073-1600 K. Products were identified with two detection methods: matrix-isolation Fourier transform infrared spectroscopy and photoionization mass spectrometry. Evidence was observed for four reactions during the breakdown of propionaldehyde: α-C-C bond scission yielding CH3CH2, CO, and H, an elimination reaction forming methylketene and H2, an isomerization pathway leading to propyne via the elimination of H2O, and a β-C-C bond scission channel forming methyl radical and (•)CH2CHO. The products identified during this experiment were CO, HCO, CH3CH2, CH3CH═C═O, H2O, CH3C≡CH, CH3, H2C═C═O, CH2CH2, CH3CH═CH2, HC≡CH, CH2CCH, H2CO, C4H2, C4H4, and CH3CHO. The first eight products result from primary or bimolecular reactions involving propionaldehyde while the remaining products occur from reactions including the initial pyrolysis products. While the pyrolysis of propionaldehyde involves reactions similar to those observed for acetaldehyde and butyraldehyde in recent studies, there are a few unique products observed which highlight the need for further study of the pyrolysis mechanism.

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The pyrolysis of 3-oxetanone, O(CH 2) 2 CO, has been studied in a resistively heated SiC tubular reactor at 400-1200 • C. Products of pyrolysis were identified via matrix-isolation FTIR spectroscopy and photoionization mass spectrometry in separate experiments. While 3-oxetanone is expected to dissociate into ketene and formaldehyde, these experiments show that ethylene oxide and carbon monoxide are also produced. Methyl radical and ethylene were observed as additional products and are thought to be the result of reactions involving ethylene oxide.