β-Ionone Reactions with the Nitrate Radical: Rate Constant and Gas-Phase Products

摘要

The bimolecular rate constant of kNO3-+β-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~l-yl)-3-buten-2-one (β-ionone) at (297 ± 3) K and 1 atmosphere total pressure. In addition, the products of β-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,0-bis(trimethylsilyl)trifluoroacetarnide 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 dini-trate, 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 p-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-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-1H-inden-2-yl)ethanone, and 5-acetyl-2-ethylidene-3-methylcyclopentanone are proposed to be the result of cyclization through a reaction intermediate.