On the stability of carbocation in water microdroplets

Abstract

Air-water system represents a ubiquitous interface that appears with a unique polar environment. Performing and studying chemistry at this interface is of growing importance for a sustainable future. Current advances in microdroplet chemistry hinted at the mysterious nature of water microdroplets, which is strikingly different from the corresponding bulk phase. Recently, we have revealed that reactive carbocation species can be captured and stabilized in water microdroplets by enhancing their lifetime up to 109 times at or nearer to the air-water interface. This result is in contrast to the expectation as carbocations are conventionally known to be rapidly annihilated by the nucleophilic attack of water. This article aims to offer some critical insights on the possible surface/interface factors, based on experiments and literature precedence, that could primarily contribute to stabilizing carbocations. How the superacidic microdroplet surface with low water density and high electric field might allow carbocation dangling at the air-water interface is discussed.