The bimolecular rate constant of kNO3+a-terpineol (16 ± 4) × 10-12 cm3 molecule-1 s-1 was measured using the relative rate technique for the reaction of the nitrate radical (NO3) with a-terpineol (2-(4-methyl-1-cyclohex-3-enyl)propan-2-ol) at 297 ± 3 K and 1 atmosphere total pressure. To more clearly define part of a-terpineol's indoor environment degradation mechanism, the products of a-terpineol + NO3 reaction were investigated. The identified reaction products were: acetone, glyoxal (HC(O)C(O)H), and methylglyoxal (CH3C(O)C(O)H). The use of derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) were used to propose the other major reaction products: 6-hydroxyhept-5-en-2-one, 4-(1-hydroxy-1-methylethyl)-1-methyl-2-oxocyclohexyl nitrate, 5-(1-hydroxy-1-methylethyl)-2-oxocyclohexyl nitrate, 1-formyl-5-hydroxy-4-(hydroxymethyl)-1,5-dimethylhexyl nitrate, and 1,4-diformyl-5-hydroxy-1,5-dimethylhexyl nitrate. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible a-terpineol + NO3* reaction mechanisms based on previously published volatile organic compound + NO3* gas-phase mechanisms. The additional gas-phase products (2,6,6-trimethyltetrahydro-2H-pyran-2,5-dicarbaldehyde and 2,2-dimethylcyclohexane-1,4-dicarbaldehyde) are proposed to be the result of cyclization through a reaction intermediate.
Quantitative-analysis; Sampling-methods; Air-quality; Indoor-environmental-quality; Chemical-binding; Chemical-deposition; Chemical-composition; Chemical-properties; Chemical-reactions; Chemical-synthesis; Organic-chemicals; Organic-compounds; Organic-vapors; Gases;
Author Keywords: a-Terpineol; Nitrate radical; Kinetics; Reaction products; Oxygenated organic compounds
Jason E. Ham, Exposure Assessment Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505