Spontaneous Generation of ⁻CH₂CN from Acetonitrile at the Air–Water Interface

Abstract

Acetonitrile (CH 3 CN) is considered a very stable molecule in aqueous solutions, and its deprotonation to produce strongly basic − CH 2 CN requires harsh conditions. CH 3 CN 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 − CH 2 CN from the CH 3 CN-H 2 O solution at the air−water interface of microdroplets, and revealed the indirect deprotonation mechanism of CH 3 CN 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 − CH 2 CN in the droplets was revealed via nucleophilic addition to acetone, benzaldehyde, and the parent CH 3 CN molecule. Furthermore, the − CH 2 CN generated in the microdroplets underwent a barrier-free nucleophilic addition reaction with CO 2 to produce 2-cyanoacetic acid for CO 2 fixation. The synergistic redox reaction process revealed in this study provides new insights into microdroplet chemistry, and the distinctive CH 3 CN reactions identified may provide new clues to unravel the mystery of the CH 3 CN transformation in the atmospheric environment.