The bimolecular rate constant of k(NO(3)(.)+beta-ionone) (9.4 +/- 2.4 x 10(-12) cm(3) molecule(-1) s(-1) was measured using the relative rate technique for the reaction of the nitrate radical (NO(3)(.)) with 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one (beta-ionone) at (297 +/- 3) K and I atmosphere total pressure. in addition, the products of beta-ionone + NO(3)(.) reaction were also investigated. The identified reaction products were glyoxal (HC(=O)C(=O)H), and methylglyoxal (CH3C(=O)C(=O)H). Derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine and N,O-bis(trimethylsilyl)trifluoroacetamide were used to propose the other major reaction products: 3-oxobutane-1,2-diyl nitrate, 2,6,6-trimethylcyclohex-1-ene-carbaldehyde, 2-oxo-1-(2,6,6-trimethylcyclohex-i-en-1-yl)ethyl nitrate, pentane-2,4-dione, 3-oxo-1-(2,6,6-trimethylcyclohex-1-en-1-yl)butane-1,2-diyl dinitrate, 3,3-dimethylcyclohexane-1,2-dione, and 4-oxopent-2-enal. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible beta-ionone + NO(3)(.) reaction mechanisms based on previously published volatile organic compound + NO(3)(.) gas-phase mechanisms. The additional gas-phase products 5-acetyl-2-ethylidene-3-methyicyclopentyl nitrate, 1-(1-hydroxy-7,7-dimetliyl-2,3,4,5,6,7-hexahydro-1H-inden-2-yl)ethanone, 1-(1-hydroxy-3a,7-dimethyl-2,3,3a,4,5,6,-hexahydro-1H-inden-2-yl)ethanone, and 5-acetyl-2-ethylidene-3-methylcyclopenta none are proposed to be the result of cyclization through a reaction intermediate.
Jason E. Ham, Exposure Assessment Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health,1095 Willowdale Road, Morgantown, WV 26505