Gas phase photolysis of pinonaldehyde in the presence of sunlight

The photolysis of pinonaldehyde in the presence of sunlight and in the presence/absence of an OH radical scavenger (cyclohexane) was studied in a large outdoor smog chamber. More than nine reaction products were identified or tentatively identified and quantified in this study using gas chromatography-mass spectrometry. Carbon yields for pinonaldehyde photolysis in the absence of an OH scavenger are: norpinonaldehyde (21.7%); pinonic acid (11.2%); 3-acetyl-2,2-dimethyl-cyclobutyl-methanol (5.3%); 2,2,3-trimethyl-cyclobutylethanone (2.9%); and 10-oxonorpinonaldehyde (1.9%). Carbon yields for pinonaldehyde photolysis in the presence of cyclohexane are: norpinonaldehyde (20.1%); pinonic acid (0.4%); 3-acetyl-2,2-dimethyl-cyclobutyl-methanol (2.7%); 2,2,3-trimethyl-cyclobutyl-ethanone (1.3%); and 10-oxonorpinonaldehyde (1.0%). The uncertainty in the yield data is estimated to be 26%. The results show that pinonaldehyde photolysis is an important part of its overall atmospheric chemistry. A detailed mechanism for pinonaldehyde photolysis in the presence/absence of cyclohexane is proposed, and a kinetic mechanism was used to simulate the gas phase reactions of pinonaldehyde. Observed temporal profiles of pinonaldehyde and its photooxidation products were used to estimate photolysis quantum yields for pinonaldehyde. The atmospheric implications of the data are discussed.