Spontaneous Generation of CHCN from Acetonitrile at the Air-Water Interface.

Acetonitrile (CHCN) is considered a very stable molecule in aqueous solutions, and its deprotonation to produce strongly basic CHCN requires harsh conditions. CHCN 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 CHCN from the CHCN-HO solution at the air-water interface of microdroplets, and revealed the indirect deprotonation mechanism of CHCN 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 CHCN in the droplets was revealed via nucleophilic addition to acetone, benzaldehyde, and the parent CHCN molecule. Furthermore, the CHCN generated in the microdroplets underwent a barrier-free nucleophilic addition reaction with CO to produce 2-cyanoacetic acid for CO fixation. The synergistic redox reaction process revealed in this study provides new insights into microdroplet chemistry, and the distinctive CHCN reactions identified may provide new clues to unravel the mystery of the CHCN transformation in the atmospheric environment.