Product formation from the gas-phase reactions of hydroxyl radicals and ozone with .beta.-phellandrene

4-Isopropyl-2-cyclohexen-1-one was identified as a product of the gas-phase reactions of β-phellandrene with OH radicals (in the presence of NO x ) and with ozone, and formation yields of 0.29±0.07 and 0.29±0.06, respectively, were determined. Sampling several 500-L volumes from the reaction chamber onto polyurethane foam solid adsorbent, followed by solvent extraction and HPLC cleanup, gave sufficient product for identification by 1 H NMR