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Published September 15, 2009 | Supplemental Material
Journal Article Open

Terpenylic Acid and Related Compounds from the Oxidation of α-Pinene: Implications for New Particle Formation and Growth above Forests


Novel secondary organic aerosol (SOA) products from the monoterpene α-pinene with unique dimer-forming properties have been identified as lactone-containing terpenoic acids, i.e., terpenylic and 2-hydroxyterpenylic acid, and diaterpenylic acid acetate. The structural characterizations were based on the synthesis of reference compounds and detailed interpretation of mass spectral data. Terpenylic acid and diaterpenylic acid acetate are early oxidation products generated upon both photooxidation and ozonolysis, while 2-hydroxyterpenylic acid is an abundant SOA tracer in ambient fine aerosol that can be explained by further oxidation of terpenylic acid. Quantum chemical calculations support that noncovalent dimer formation involving double hydrogen bonding interactions between carboxyl groups of the monomers is energetically favorable. The molecular properties allow us to explain initial particle formation in laboratory chamber experiments and are suggested to play a role in new particle formation and growth above forests, a natural phenomenon that has fascinated scientists for more than a century.

Additional Information

© 2009 American Chemical Society. Received March 11, 2009. Revised manuscript received June 6, 2009. Accepted July 29, 2009. Publication Date (Web): August 18, 2009. This study was financially supported by the following organizations: for Universities of Antwerp (UA) and Ghent, Belgian Federal Science Policy Office, Research Foundation - Flanders, and the EU commission (Marie Curie Intra-European fellowship; contract no. 039787-SOAMASS); for Leibniz-Institut fr Troposphrenforschung, Deutsche Forschungsgemeinschaft; and for California Institute of Technology, U.S. Department of Energy, U.S. Environmental Protection Agency, and U.S. National Science Foundation. We also acknowledge the UA for access to CalcUA, the university's supercomputer cluster. Supporting Information: Experimental information on α-pinene ozonolysis samples and preparation of standards; additional results and discussion on the formation of TA and DTAA through ozonolysis and photooxidation of α-pinene; structure and mass spectrometric characterization of DTAA and 2-hydroxyterpenylic acid; and characterization of additional MW 188 compounds in α-pinene SOA. This material is available free of charge via the Internet at http://pubs.acs.org.

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August 19, 2023
October 19, 2023