Infrared Absorption Spectrum of the Simplest Criegee Intermediate CH ₂ OO

Abstract

The Criegee intermediates are carbonyl oxides postulated to play key roles in the reactions of ozone with unsaturated hydrocarbons; these reactions constitute an important mechanism for the removal of unsaturated hydrocarbons and for the production of OH in the atmosphere. Here, we report the transient infrared (IR) absorption spectrum of the simplest Criegee intermediate CH2OO, produced from CH2I + O2 in a flow reactor, using a step-scan Fourier-transform spectrometer. The five observed bands provide definitive identification of this intermediate. The observed vibrational frequencies are more consistent with a zwitterion rather than a diradical structure of CH2OO. The direct IR detection of CH2OO should prove useful for kinetic and mechanistic investigations of the Criegee mechanism.

High resolution quantum cascade laser spectroscopy of the simplest Criegee intermediate, CH2OO, between 1273 cm−1 and 1290 cm−1

“…The main advantages of the QCL spectrometer are higher resolution and higher sensitivity than those of the conventional step-scan FTIR (ss-FTIR) spectrometer, 29,30 although the latter Compared to ss-FTIR, our QCL spectrometer is more suitable for probing CH 2 OO in kinetic studies due to the following key factors: (1) A rapid intrapulse frequency scan at a high repetition rate allows for obtaining time-resolved spectra within the lifetime of CH 2 OO; (2) Our multipass cell has a smaller volume (191 cm 3 versus 1370 cm 3 in Ref. 29 ), thus smaller amounts of reactants are required; (3) The QCL spectrometer has a higher sensitivity and can therefore work with a lower concentration of CH 2 OO, which leads to a longer lifetime.…”

“…It is highly desirable to extend the lifetime of CH 2 OO for kinetic studies, because then slower reactions can be investigated. Due to lower sensitivity, previous FT-IR studies 29,30 have had to use higher CH 2 OO concentrations, which led to shorter lifetimes in the range of 15−150 µs.…”

The Molecular Identification of Organic Compounds in the Atmosphere: State of the Art and Challenges

“…566 More recently IR spectroscopy was also used for the detection of Criegee intermediates, 568 including in gas-phase ozonolysis reactions. 569 The investigation of Criegee intermediates is now a rapidly expanding field of research, in which the development of techniques for their detection in the atmosphere will be an important direction.…”

Night-time measurements of HO<sub><i>x</i></sub> during the RONOCO project and analysis of the sources of HO<sub>2</sub>

“…The primary ozonide decomposes to form one of two possible pairs of products, each pair consisting of a carbonyl compound and a vibrationally and rotationally excited carbonyl oxide termed a Criegee intermediate (CI). The simplest gas-phase CI, CH 2 OO, and the alkylsubstituted CH 3 CHOO have been observed directly by photoionisation mass spectrometry (Taatjes et al, 2008(Taatjes et al, , 2013Beames et al, 2012Beames et al, , 2013Welz et al, 2012;Stone et al, 2014a), by infrared absorption spectroscopy (Su et al, 2013), and by microwave spectroscopy Endo, 2013, 2014). Excited CIs may be stabilised by collision with surrounding molecules Drozd and Donahue, 2011) or may undergo isomerisation or decomposition to yield products including OH, H, and subsequently HO 2 (Paulson and Orlando, 1996;Kroll et al, 2001aKroll et al, , b, 2002Johnson and Marston, 2008).…”