Direct Kinetic Measurements of Reactions between the Simplest Criegee Intermediate CH sub(2)OO and Alkenes

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 118; no. 11; pp. 1997 - 2006-1997-2006
• Main Authors: Buras, Zachary J, Elsamra, Rehab MI, Jalan, Amrit, Middaugh, Joshua E, Green, William H
• Format: Journal Article
• Language: English
• Published: 01.03.2014
• Subjects: Alkenes; Atmospherics; Estimates; Ethene; Lasers; Mathematical analysis; Rate constants; Reaction kinetics
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp4118985

The simplest Criegee Intermediate (CH sub(2)OO), a well-known biradical formed in alkene ozonolysis, is known to add across double bonds. Here we report direct experimental rate measurements of the simplest Criegee Intermediate reacting with C2-C4 alkenes obtained using the laser flash photolysis technique probing the recently measured B super(1)A' arrow left X super(1)A' transition in CH sub(2)OO. The measured activation energy (298-494 K) for CH sub(2)OO + alkenes is E sub(a) approximately 3500 plus or minus 1000 J mol super(-1) for all alkyl substituted alkenes and E sub(a) = 7000 plus or minus 900 J mol super(-1) for ethene. The measured Arrhenius pre-exponential factors (A) vary between (2 plus or minus 1) 10 super(-15) and (11 plus or minus 3) 10 super(-15) cm super(3) molecule super(-1) s super(-1). Quantum chemical calculations of the corresponding rate coefficients reproduce qualitative reactivity trends but overestimate the absolute rate coefficients. Despite the small E sub(a)'s, the CH sub(2)OO + alkene rate coefficients are almost 2 orders of magnitude smaller than those of similar reactions between CH sub(2)OO and carbonyl compounds. Using the rate constants measured here, we estimate that, under typical atmospheric conditions, reaction with alkenes does not represent a significant sink of CH sub(2)OO. In environments rich in C=C double bonds, however, such as ozone-exposed rubber or emission plumes, these reactions can play a significant role.