β-Ionone reactions with the nitrate radical: Rate constant and gas-phase products

Abstract

The bimolecular rate constant of k (9.4 ± 2.4 × 10−12 cm3 molecule−1 s−1 was measured using the relative rate technique for the reaction of the nitrate radical (NO3•) with 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one (β-ionone) at (297 ± 3) K and 1 atmosphere total pressure. In addition, the products of β-ionone + NO3• 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-1-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 β-ionone + NO3• reaction mechanisms based on previously published volatile organic compound + NO3• gas-phase mechanisms. The additional gas-phase products 5-acetyl-2-ethylidene-3-methylcyclopentyl nitrate, 1-(1-hydroxy-7,7-dimethyl-2,3,4,5,6,7-hexahydro-1 H-inden-2-yl)ethanone, 1-(1-hydroxy-3a,7-dimethyl-2,3,3a,4,5,6,-hexahydro-1 H-inden-2-yl)ethanone, and 5-acetyl-2-ethylidene-3-methylcyclopentanone are proposed to be the result of cyclization through a reaction intermediate. © 2009 Wiley Periodicals, Inc.*1 Int J Chem Kinet 41: 629–641, 2009