Paul Ziemann Department of Chemistry & CIRES University of Colorado at Boulder

Gas- and Particle-Phase Products and their Mechanisms of Formation from the Reactions of Monoterpenes with N 3 Radicals: Comprehensive Measurements and Modeling Paul Ziemann Department of Chemistry & CIRES University of Colorado at Boulder

Gas- and Particle-Phase Products and their Mechanisms of Formation from the Reactions of Monoterpenes with N3 Radicals: Comprehensive Measurements and Modeling Paul Ziemann Department of Chemistry & CIRES University of Colorado at Boulder Megan Claflin

Southern xidant & Aerosol Study (SAS) Investigate the role of interactions among anthropogenic and biogenic emissions on air quality ( 3 and SA) Biogenic VCs are the most abundant class of VCs emitted Isoprene and monoterpenes are ~ 70% of ~1000 Tg yr 1 global emissions Conducted lab studies of oxidation of monoterpenes & isoprene to determine functional group composition for SAS-lab comparison

Ambient rganic Nitrates (J.(J. Geophys. Geophys. Res., Res., 2010) 2010) (PNAS, 2015) (Atmos. Chem. Phys, 2017) (Atmos. Chem. Phys., 2016) (Atmos. Chem. Phys, 2013) (PNAS, 2016) (Atmos. Chem. Phys, 2015) (Atmos. Chem. Phys, 2015)

Reactions of Monoterpenes (mostly b-pinene) + N 3 Radicals

Methods Functional Group Composition Deriv-Spec FTIR 8 m 3 FEP Teflon Environmental Chamber 55% RH Deliquesced (NH 4 ) 2 S 4 Seed Particles 1 ppm b-pinene 0.33 ppm N 2 5 N 3 + N 2 Filter Sampling DNPH Cartridges PFBHA Denuder Molecular Analysis HPLC Tenax GC-FID SMPS TDPBMS EI-MS b-pinene + N 3 reaction & SA formation complete in ~10 min TD-CI-ITMS ESI-MS Gas Sampling Particle Sampling ff-line Analysis

Mechanism of Reaction of b-pinene + N 3 Radicals N 2 N 2 + N 3 + N 3 β-pinene + 2 N 2 H N 2 R 2 HN N 2 R R 2 or N 3 N 2 + H H + Decomp N 2 Formaldehyde Nopinone Decomp + 2 N R 2 2 + H HCN N 2 N 2 R 2 or N 3 N 2 DCN o H N 2 Decomp + 2 N 2 HDCN N 2 TCN + R 2 N 2 N 2 R 2 N 2 H HDCN N 2 HCNA H H N 2 + Acetone

Multifunctional Gas-Phase Products

SA Product Separation & Quantitation: HPLC-UV Measure nitrate absorbance at 210 nm Quantify using authentic standard of Peak 6 compound

SA Product Identification: Mass Spectrometry Peak 6 Diacetal formation < 1 min

SA Products & Mass Fractions 95% of SA mass identified and quantified

SA Product Molar Yields Peak Number Monomer and ligomers Mole MW of Molar Fraction Product Yield (%) (%) Monomer ID Monomer Building Blocks Mole MW of Fraction Monomer (%) Molar Yield (%) 1 245 6.5 2.0 HN 215 37.8 23.6 2a 460 7.3 2.2 DCN 229 4.7 2.9 2b 444 3.6 1.1 HCN 231 41.5 25.9 2c 476 5.9 1.8 TCN 245 3.2 2.0 3 444 8.4 2.6 HDCN 247 7.7 4.8 4 460 4.4 1.4 HCNA 263 5.1 3.2 5 657 9.5 2.9 6 428 54.4 16.7 Total monomer molar yield = 62.4% Based on 10 130 min filter samples corrected for particle wall loss

Deriv-Spec Functional Group Analysis Carbonyl Ester Carboxyl Hydroxyl Peroxide Nitrate Carbonyl, ester, carboxyl, hydroxyl: derivatize Peroxide: oxidize 2I to I 2 Nitrate Measure UV-Vis absorbance Quantify using surrogate standards

SA Bulk Functional Group Analysis Deriv-Spec FTIR Functional groups per C 10 molecule No -H C-H C= N 2 with CH 2 without CH 2

SA Functional Group Composition: Bulk vs. Molecular Analysis Bulk Molecular Deriv-Spec HPLC-UV-MS Functional FG/C Group 10 Molecule Peroxide 0.02 0.00 Ester 0.01 0.00 Carbonyl 0.43 0.40 Carboxyl 0.06 0.05 Hydroxyl 0.00 0.00 Nitrate 1.12 1.00 Methylene 8.37 8.55 *Estimated based on rate of sucrose hydrolysis at same ph * SA results: Claflin & Ziemann, JPCA, 2018

Mechanism of Reaction of β-pinene + N 3 Radicals N 2 N 2 + N 3 + N 3 Molar yields ParQcle phase = 62.4% β-pinene + 2 N 2 R 2 N 2 H HN 23.6% N 2 + Yeh & Ziemann, JPCA, 2015 Vereecken & Peeters, PCCP, 2009, 2010 H H Formaldehyde + Decomp Nopinone N 2 R 2 or N 3 N 2 Decomp + 2 N R 2 2 N 2 R 2 or N 3 N 2 R N 2 <1% No peroxide dimers No R 2 + H 2 No R 2 + N 3 (N 2 5 Δβ-pinene = 20 ppb) + H HCN DCN 25.9% 2.9% isomer 2.0% o N 2 HDCN N 2 TCN + H R 2 N 2 N 2 Decomp + 2 N 2 R 2 N 2 H HDCN 4.8% isomer 3.2% N 2 HCNA H H N 2 + Acetone

Unobserved Potential Additional Pathways Vereecken & Peeters PCCP, 2012 b-pinene + H 70% ring opening: 30% 2 Exothermicity (kcal mol 1 ) H ~30: N 3 ~20 No dinitrates No peroxides

Conclusions Identified and quantified essentially all gas- and particle phase products from b-pinene + N 3 radical reaction Developed quantitative gas- and particle-phase reaction mechanism and model Demonstrates importance of particle-phase reactions in SA formation needs to be in models May be similar chemistry for other monoterpenes Future work includes: > ther monoterpenes > High H 2 and autoxidation conditions