Microwave assisted bi-functional activation of β-bromo-tert-alcohols

Photolysis of Gas-Phase Atmospherically Relevant Monoterpene-Derived Organic Nitrates

Organic nitrates (ONs) can impact spatial distribution of reactive nitrogen species and ozone formation in the atmosphere. While photolysis of ONs is known to result in the release of NO₂ back to the atmosphere, the photolysis rate constants and mechanisms of monoterpene-derived ONs (MT-ONs) have not been well constrained. We investigated the gas-phase photolysis of three synthetic ONs derived from α-pinene, β-pinene, and d-limonene through chamber experiments. The measured photolysis rate constants ranged from (0.55 ± 0.10) × 10^-5 to (2.3 ± 0.80) × 10^-5 s^-1 under chamber black lights. When extrapolated to solar spectral photon flux at a solar zenith angle of 28.14° in summer, the photolysis rate constants were in the range of (4.1 ± 1.4) × 10^-5 to (14 ± 6.7) × 10^-5 s^-1 (corresponding to lifetimes of 2.0 ± 0.96 to 6.8 ± 2.4 h) and (1.7 ± 0.60) × 10^-5 to (8.3 ± 4.0) ×10^-5 s^-1 (3.3 ± 1.6 to 17 ± 6.0 h lifetimes) by using wavelength-dependent and average quantum yields, respectively. Photolysis mechanisms were proposed based on major products detected during photolysis. A zero-dimensional box model was further employed to simulate the photolysis of α-pinene-derived ON under ambient conditions. We found that more than 99% of α-pinene-derived ON can be converted to inorganic nitrogen within 12 h of irradiation and ozone was formed correspondingly. Together, these findings show that photolysis is an important atmospheric sink for MT-ONs and highlight their role in NO_x recycling and ozone chemistry.

Chemical Synthesis of Multifunctional Air Pollutants: Terpene-Derived Nitrooxy Organosulfates

Nitrooxy organosulfates derived from terpenes (NOS_TP) represent an important class of products formed between anthropogenic pollution (e.g., SO₂ and NO_x) and natural emissions. NOS_TP compounds have been consistently detected in atmospheric environments under varying urban influences. Their chemical linkages to both anthroposphere and biosphere make them valuable markers for tracking anthroposphere-biosphere interactions. However, their quantification, formation, and transformation kinetics in atmospheric aerosols are hindered due to the lack of NOS_TP standards. In this work, we developed two routes for the first concise chemical synthesis of eight NOS_TP from terpenes including α-pinene, β-pinene, limonene, limonaketone, and β-caryophyllene. Subsequently, six of the synthesized NOS_TP were for the first time positively identified in ambient aerosol samples, clarifying certain misidentifications in previous studies. More significantly, the availability of authentic standards allows irrefutable observation of three carbon skeleton-rearranged NOS_TP, two derived from α-pinene, and one derived from β-caryophyllene, revealing the occurrence of previously unrecognized transformation pathways in the formation of NOS_TP. Two synthesized NOS_TP from β-pinene and limonene could not be detected, likely due to rapid hydrolysis of their immediate hydroxynitrate precursors outcompeting sulfation. Such mechanistic evidence is valuable in understanding the atmospheric chemistry of NOS_TP and related compounds. This work demonstrates the usefulness of authentic standards in probing the NOS_TP formation mechanisms in the atmosphere. Comparison of NOS_TP ambient samples collected from four Chinese cities in two winter months indicates that anthropogenic chemical factors could outcompete terpene emissions in the formation of NOS_TP.