Direct Determination of the Simplest Criegee Intermediate (CH2OO) Self Reaction Rate

• Published in: The journal of physical chemistry letters 2014-07, Vol.5 (13), p.2224-2228
• Main Authors: Buras, Zachary J, Elsamra, Rehab M. I, Green, William H
• Format: Article
• Language: English
• Subjects: biofuels (including algae and biomass), hydrogen and fuel cells, combustion, carbon capture; Kinetics and Dynamics
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/jz5008406

The rate of self-reaction of the simplest Criegee intermediate, CH2OO, is of importance in many current laboratory experiments where CH2OO concentrations are high, such as flash photolysis and alkene ozonolysis. Using laser flash photolysis while simultaneously probing both CH2OO and I atom by direct absorption, we can accurately determine absolute CH2OO concentrations as well as the UV absorption cross section of CH2OO at our probe wavelength (λ = 375 nm), which is in agreement with a recently published value. Knowing absolute concentrations we can accurately measure k self = 6.0 ± 2.1 × 10–11cm3 molecule–1 s–1 at 297 K. We are also able to put an upper bound on the rate coefficient for CH2OO + I of 1.0 × 10–11 cm3 molecule–1 s–1. Both of these rate coefficients are at least a factor of 5 smaller than other recent measurements of the same reactions.