Acetonitrile (CH₃CN) is considered a very stable molecule in aqueous solutions, and its deprotonation to produce strongly basic ⁻CH₂CN requires harsh conditions. CH₃CN is also present in the atmosphere, but its chemical transformation pathway at the air–water interface is unknown. In this study, we discovered and verified the unprecedented spontaneous generation of ⁻CH₂CN from the CH₃CN-H₂O solution at the air–water interface of microdroplets, and revealed the indirect deprotonation mechanism of CH₃CN by synergistic redox of ^•OH and electrons in the microdroplets through the capture of key intermediates and computational chemistry. In addition, the dynamic process of indirect deprotonation–protonation was also observed. The high reactivity of ^–CH₂CN in the droplets was revealed via nucleophilic addition to acetone, benzaldehyde, and the parent CH₃CN molecule. Furthermore, the ^–CH₂CN generated in the microdroplets underwent a barrier-free nucleophilic addition reaction with CO₂ to produce 2-cyanoacetic acid for CO₂ fixation. The synergistic redox reaction process revealed in this study provides new insights into microdroplet chemistry, and the distinctive CH₃CN reactions identified may provide new clues to unravel the mystery of the CH₃CN transformation in the atmospheric environment.

中文翻译：

---

乙腈在空气-水界面自发生成 −CH2CN


乙腈 （CH₃CN） 在水溶液中被认为是一种非常稳定的分子，其去质子化产生强碱性 ⁻CH₂CN 需要苛刻的条件。CH₃CN 也存在于大气中，但其在空气-水界面的化学转化途径尚不清楚。在这项研究中，我们发现并验证了 CH₃CN-H₂O 溶液在微滴气-水界面处前所未有的自发产生 ⁻CH₂CN，并揭示了 CH₃CN 的间接去质子化机制 ^•OH 和电子在微滴中通过捕获关键中间体和计算化学。此外，还观察到间接去质子化-质子化的动态过程。通过对丙酮、苯甲醛和母体 CH₃CN 分子的亲核加成，揭示了液滴中 ^–CH₂CN 的高反应性。此外，微滴中产生的 ^–CH₂CN 与 CO₂ 发生无障碍亲核加成反应，生成用于 CO₂ 固定的 2-氰乙酸。本研究揭示的协同氧化还原反应过程为微滴化学提供了新的见解，而鉴定出的独特 CH₃CN 反应可能为解开大气环境中 CH₃CN 转化的神秘面纱提供新的线索。