methyl-radical and ketene

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.

Topics: Carbon Monoxide; Ethers, Cyclic; Ethylene Oxide; Ethylenes; Formaldehyde; Gases; Ketones; Mass Spectrometry; Methane; Spectroscopy, Fourier Transform Infrared; Temperature

The hyperfine coupling constants (hfcs) of two methyl radical isotopomers, CH2Mu and CD2Mu, have been measured over a wide range of temperature in ketene and ketene-d2, from which the radicals were generated. The magnitudes of the hfcs of these muoniated methyl radical isotopomers are larger than those of CH3 and CD3 due to larger zero-point energy in the out-of-plane bending mode. In contrast to CH3 and CD3, where the coupling constants become smaller with increasing temperature, the negative hfcs of the muoniated radicals were found to increase in magnitude (become more negative) with temperature, passing through a maximum near the boiling point of ketene. This behavior is attributed to a solvent-induced change in the force constant of the out-of-plane bending mode. The opposite temperature effect known for CH3 and CD3 is explained by excitation of the low frequency out-of-plane bending mode. This effect is much smaller in the muoniated radicals, where the vibrational frequency is significantly higher due to the light mass of muonium; consequently, the solvent effect dominates at low temperatures.

Topics: Algorithms; Cold Temperature; Deuterium; Electron Spin Resonance Spectroscopy; Ethylenes; Free Radicals; Isomerism; Isotopes; Ketones; Methane; Solvents; Transition Temperature