Reactivity of a Carene-Derived Hydroxynitrate in Mixed Organic/Aqueous Matrices: Applying Synthetic Chemistry to Product Identification and Mechanistic Implications

Addison B Mcalister,Anthony J Carrasquillo,Gabriela M Bailey,Nicole P Kretekos,Emily J Mclaughlin Sta Maria,Aaron Huang,Petra R Baldwin,Rebecca Lyn Lalonde,James I Vesto,Kathryn A Wright

doi:10.3390/atmos12121617

Addison B Mcalister, Anthony J Carrasquillo + Show 8 more

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https://doi.org/10.3390/atmos12121617

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Journal: Atmosphere	Publication Date: Dec 3, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Reed College, Williams College

Abstract

β-hydroxynitrates (HN) are a major class of products formed during OH and NO3 initiated oxidation of terpenes. Their production contributes significantly to secondary organic aerosol (SOA) formation and NOx sequestration. However, studying the condensed phase reactions of this important class of molecules has been hindered by the lack of commercially available authentic standards. The goal of this work was to examine the influence of water concentration and solvent identity on product yields of a tertiary HN derived from 3-carene prepared in house. To assess the role of water on conversion chemistry, bulk-phase reactions were conducted in DMSO-d6, a non-nucleophilic solvent, with a gradient of water concentrations, and analyzed with 1H NMR. Product identifications were made by comparison with authentic standards prepared in house. Four major products were identified, including an unexpected diol produced from carbocation rearrangement, diol diastereomers, and trans-3-carene oxide, with varying yields as a function of water concentration. Product yields were also measured in two protic, nucleophilic solvents, MeOD-d4 and EtOD-d6. Finally, reactions with added chloride formed alkyl chloride products in yields approaching 30%. These results are among the first to highlight the complexities of nucleophilic reactions of hydroxynitrates in bulk, mixed aqueous/organic media and to identify new, unexpected products.

Highlights

The effects of aerosol on human health and the climate system have been well documented, and it is well established that the magnitude of the impact on each depends strongly on particle size and chemistry
Hydroxynitrates (HN) are one of the major classes of oxidation products formed in the atmosphere, following the OH or NO3 radical-initiated oxidation of volatile organic compounds (VOCs) [1–5]
IR spectra were recorded on a ThermoNicolet IR 100 spectrometer using a Thunderdome attenuated total reflectance (ATR) sample accessory

Summary

Introduction

The effects of aerosol on human health and the climate system have been well documented, and it is well established that the magnitude of the impact on each depends strongly on particle size and chemistry. The organic fraction of aerosol represents the most complex and poorly understood type of aerosol due to the wide range of processes and chemical species involved in its formation. During its atmospheric lifetime, an aerosol particle is subjected to a myriad of physical and chemical processes that conspire to alter the chemical composition of the particle. Atmospheric condensed-phase reactivity is likely to differ substantially from the gas phase due to the drastic differences in molecular environments. Gas phase studies are disproportionately conducted relative to studies of condensed-phase reactions, this chemistry remains poorly understood.

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