Direct Measurements of Conformer-Dependent Reactivity of the Criegee Intermediate CH_3CHOO

摘要

Ozonolysis of alkenes is generally understood to proceed via a 1,3-cycloaddition of ozone across the olefinic bond to produce a primary ozonide, the decomposition of which forms a carbonyl moiety and a Criegee intermediate (CI) (1). The fate of the CI determines the end products of the ozonolysis reaction and can have a substantial impact on the atmosphere (1-4). Recently, the simplest CI, CH_2OO, has been directly produced in the gas phase with low internal energies from reaction of O_2 with CH_3SOCH_2 (5,6) or CH_2I (4, 7,8) and unambiguously detected by tunable synchrotron or laser photoionization mass spectrometry. These techniques allowed direct measurements of the reaction kinetics of CH2OO with several important tropospheric species, including SO_2 and NO_2, both of which react much faster with CH_2OO than models had assumed (4). Since those direct measurements appeared, new high-level calculations (9), field measurements (10), and ozonolysis experiments (10-12) continue to suggest that CI reactions are important in tropospheric sulfate chemistry.