Formation and reactions of 2-formylcinnamaldehyde in the OH radical-initiated reaction of naphthalene.
2-Formylcinnamaldehyde [O-HC(O)C6H4CH=CHCHO] is a major product of the OH radical-initiated reaction of naphthalene, the atmospherically most abundant polycyclic aromatic hydrocarbon. Previous studies indicate that 2-formylcinnamaldehyde undergoes photolysis as well as reaction with OH radicals. We have used direct air sampling atmospheric pressure ionization mass spectrometry (API-MS) to monitor 2-formylcinnamaldehyde as its protonated molecular ion during OH radical-initiated reactions of naphthalene. From the time-dependent behavior of the 2-formylcinnamaldehyde signal, ratios of (2-formylcinnamaldehyde removal rate/naphthalene reaction rate) were determined over a range of approximately 3 in (OH radical concentration/ light intensity). With an estimated rate constant for the reaction of OH radicals with 2-formylcinnamaldehyde of 5.3 x 10(-11) cm3 molecule(-1) s(-1), the photolysis rate of 2-formylcinnamaldhyde by blacklamps was determined to be approximately equal to that of NO2. Photolysis of 2-formylcinnamaldehyde will be the dominant loss process in the atmosphere, with an estimated lifetime of 2-formylcinnamaldehyde of approximately 120 s at a solar zenith angle of 30 degrees. Our data were used to re-evaluate the previous 2-formylcinnamaldehyde measurements of Sasaki et al. (Environ. Sci. Technol. 1997, 31, 3173-3179) and derive a 2-formylcinnamaldehyde formation yield from the OH radical reaction of naphthalene in the presence of NO of 56(-10)(+15)%.
Air Pollution Research Center, University of California Riverside, California 92521, USA.
Noriko
N
Nishino
Janet
J
Arey
Roger
R
Atkinson
D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D009281:Naphthalenes / Q000737:chemistry*; D010782:Photolysis; D009764:o-Phthalaldehyde / Q000031:analogs & derivatives / Q000737:chemistry*
C540086:2-formylcinnamaldehyde; D009281:Naphthalenes; C031721:naphthalene; D017665:Hydroxyl Radical; D009764:o-Phthalaldehyde