Terpene-derived acids formed through the atmospheric gas-phase oxidation of terpenes are able to efficiently undergo a phase transfer into the aqueous phase. The subsequent aqueous-phase oxidation of such compounds has not been intensely studied. Accordingly, the aqueous-phase second-order rate constants of the oxidation reactions of cis-pinonic acid (CPA) and (+)-camphoric acid (+CA) with hydroxyl radicals (^•OH), nitrate radicals (NO₃^•), and sulfate radicals (SO₄^•–) were investigated as a function of temperature and pH in the present study. For CPA and +CA the following ^•OH reaction rate constants at T = 298 K are determined: k_second(CPA, pH<2) = (2.8 ± 0.1) × 10⁹ L mol^–1 s^–1, k_second(CPA, pH>8) = (2.7 ± 0.3) × 10⁹ L mol^–1 s^–1, k_second(+CA, pH<2) = (2.1 ± 0.1) × 10⁹ L mol^–1 s^–1, k_second(+CA, pH=5.3) = (2.7 ± 0.3) × 10⁹ L mol^–1 s^–1, k_second(+CA, pH>8) = (2.7 ± 0.1) × 10⁹ L mol^–1 s^–1. In order to assess the atmospheric impact of the aqueous-phase oxidation of such compounds, atmospheric aqueous-phase lifetimes were calculated for two model scenarios based on CAPRAM 3.0i. The aqueous-phase oxidation under remote conditions emerges to be the most favored pathway with lifetimes of 5 ± 1 h.

中文翻译：

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大气相关自由基对萜烯衍生酸的水相氧化

通过萜烯在大气中的气相氧化形成的萜烯衍生的酸能够有效地进行相转移到水相中。此类化合物随后的水相氧化尚未得到深入研究。因此，顺式-己酸（CPA）和（+）-樟脑酸（+ CA）与羟基（^• OH），硝酸根（NO ₃ ^•），在本研究中，研究了硫酸根（SO ₄ ^•–）与温度和pH的关系。对于CPA和+ CA，确定以下条件^• T = 298 K时的OH反应速率常数：k_秒（CPA，pH <2）=（2.8±0.1）×10 ⁹ L摩尔^–1 s ^–1，k_秒（CPA，pH> 8）=（2.7±0.3）×10 ⁹ L摩尔^–1 s ^–1，k_秒（+ CA，pH <2）=（2.1±0.1）×10 ⁹ L摩尔^–1 s ^–1，k_秒（+ CA，pH = 5.3）=（2.7±0.3）×10 ⁹ L摩尔^{– 1} s ^–1，k_秒（+ CA，pH> 8）=（2.7±0.1）×10 ⁹ L mol ^–1 s ^–1。为了评估此类化合物的水相氧化对大气的影响，基于CAPRAM 3.0i，针对两种模型方案计算了大气水相寿命。在偏远条件下，水相氧化成为最受青睐的途径，其寿命为5±1 h。