Product and Mechanistic Study of the Reaction of NO₃ Radicals with α-Pinene

The reaction between NO 3 and α-pinene has been studied in large reaction chambers of 0.5−200 m 3 volume, using long path FT-IR, GC-ECD, and GC-FID for the analyses. The reaction yielded 62 ± 4% pinonaldehyde (3-acetyl-2,2-dimethylcyclobutane acetaldehyde) and 3 ± 0.5% pinane epoxide. The total yield of alkylnitrates was estimated to be approximately 14%; two of the nitrates have been identified as 3-oxypinane-2-nitrate, and 2-hydroxy-3-nitrate with yields of 3 ± 0.2% and 5 ± 0.4%, respectively. This work represents the first quantitative identification of pinonaldehyde and alkylnitrates from the reaction of NO 3 with α-pinene. A thermally stable peroxy acylnitrate was observed to be formed from secondary reactions of pinonaldehyde in the system. This compound has been assigned to 3-acetyl-2,2-dimethylcyclobutane acetylperoxynitrate. Possible implications for the atmospheric NO x chemistry are discussed. From the product data, a mechanism for the NO 3 + α-pinene reaction has been constructed.