Atmospheric fate of carbonyl oxidation products originating from α-pinene and Δ3-carene : Determination of rate of reaction with OH and NO3 radicals, UV absorption cross sections, and vapor pressures

Large yields of dicarbonyl compounds have been found in the atmospheric oxidation of α-pinene and Δ3-carene. These terpenes are emitted in large quantities by biogenic sources, and it is important to know the fate of their reaction products. In this investigation, ultraviolet and infrared absorption cross sections, vapor pressures, and rate coef ficients for hydroxyl and nitrate radical reactions have been determined for the main product in each case, i.e., 3-acetyl-2,2-dimethylcyclobutaneacetaldehyde (pinonaldehyde) and 2,2-dimethyl-3-(2-oxopropyl)cyclopropaneacetaldehyde (caronaldehyde). Photolysis lifetimes at noon on July 1 at 50° N using a photolysis quantum yield of 1 are 3.3 h for pinonaldehyde and 5.8 h for caronaldehyde. The infrared absorption cross sections obtained (base e) were (8.08 ± 0.32) × 10-19 and (1.04 ± 0.05) × 10-18 cm2 molecule-1 for pinonaldehyde and caronaldehyde at 1725.4 and 1741.5 cm-1, respectively. Vapour pressures determined by Knudsen effusion measurements are 5.1 and 3.0 P...