Abstract View
Synthesis and Hydrolysis of Atmospherically Relevant Monoterpene Organic Nitrates
YUCHEN WANG, Masayuki Takeuchi, Tianchang Xu, Amanda J Schwartz, Ivan Piletic, Stefan France, Nga Lee Ng, Georgia Institute of Technology
Abstract Number: 301
Working Group: Aerosol Chemistry
Abstract
Partition of gas phase organic nitrates (ON) to aerosols and subsequent hydrolysis has been identified as an important loss approach for ON species. Considering the different hydrolysis lifetimes, ONs may act as a permanent sink or temporary reservoir of NOx, which further impact NOx recycling, O3 formation, and SOA formation. However, the hydrolysis mechanisms and the major factors controlling the hydrolysis lifetime are not fully understood. To systematically investigate ON hydrolysis, we synthesized six monoterpene hydroxy nitrates and two ketone nitrates based on two unified synthetic strategies. In situ nuclear magnetic resonance and high-resolution time-of-flight chemical-ionization mass spectrometer (HR-ToF-CIMS) coupled with the filter inlet for gases and aerosols (FIGAERO) were utilized for determining the hydrolysis rate constants for these synthetic standards. We observed that the hydrolysis lifetimes are in the range of 13 mins to 10.1 h for allylic primary ON and tertiary ON but there is no depletion for secondary ON for seven days in neutral condition. The ON hydrolysis was hypothesized to proceed via an acid catalyzed SN1 mechanism through carbocation intermediate. In our detection, the number of alkyl substitutions, functional groups in adjacent position of nitrooxy group, and carbon skeleton are proposed to be three important factors controlling hydrolysis rates. The degraded products were identified by liquid chromatography-Orbitrap mass spectrometry (LC-Orbitrap MS) and enthalpies were calculated by density-functional theory (DFT). These findings provide new insights into ON hydrolysis mechanism, assessment of ON as NOx reservoirs/sinks, and fate of atmospheric ON.