Mechanism for the formation of gaseous and particulate products from ozone-cycloalkene reactions in air

Abstract

Both gaseous and particulate products of the reactions of ozone with C/sub 5/ and C/sub 7/ cycloalkenes in air were analyzed. Major gaseous products were CO, CO/sub 2/, formic acid, and aldehydes consisting of C/sub n/ dialdehyde, C/sub n-1/ dialdehyde, and C/sub n-1/ monoaldehyde. The sums of the primary yields of aldehydes were 34 +/- 15% for cyclopentene and 64 +/- 15% for cycloheptene. In cyclopentene reactions, formaldehyde and ethylene were additional major products with yields of 13 +/- 3% and 12 +/- 2%, respectively. The main particulate products were C/sub n/ and C/sub n-1/ dialdehyde, omega-oxo carboxylic acid, and dicarboxylic acid, and the absolute yields of each component were determined as a function of ellapsed time after the reaction. Transformation of aerosols was clearly demonstrated to be dialdehyde ..-->.. omega-oxo carboxylic acid ..-->.. dicarboxylic acid. A generalized mechanism of the ozone-cycloalkene reactions was proposed, and the branching ratio of each pathway of the Criegee-type intermediates was evaluated. The lower and upper limits of aerosol yield were determined to be 1 +/- 1 and approx. 5%, 3 +/- 1 and 13 +/- 3%, and 4 +/- 1 and approx. 10% for C/sub 5/, C/sub 6/, and C/sub 7/ cycloalkenes, respectively.more » 37 references, 1 figure,5 tables.« less