A Signature of Roaming Dynamics in the Thermal Decomposition of Ethyl Nitrite: Chirped-Pulse Rotational Spectroscopy and Kinetic Modeling

Chirped-pulse
(CP) Fourier transform rotational spectroscopy is
uniquely suited for near-universal quantitative detection and structural
characterization of mixtures that contain multiple molecular and radical
species. In this work, we employ CP spectroscopy to measure product
branching and extract information about the reaction mechanism, guided
by kinetic modeling. Pyrolysis of ethyl nitrite, CH3CH2ONO, is studied in a Chen type flash pyrolysis reactor at
temperatures of 1000–1800 K. The branching between HNO, CH2O, and CH3CHO products is measured and compared
to the kinetic models generated by the Reaction Mechanism Generator
software. We find that roaming CH3CH2ONO →
CH3CHO + HNO plays an important role in the thermal decomposition
of ethyl nitrite, with its rate, at 1000 K, comparable to that of
the radical elimination channel CH3CH2ONO →
CH3CH2O + NO. HNO is a signature of roaming
in this system.