Hydrated acid clusters.

The nature of acids in an aqueous environment is fundamental to many aspects of chemistry. The defining feature of an acid is its ability to transfer a proton to water, but this seemingly simple process can be complex and highly dependent on solvation. This review describes studies aimed at obtaining molecular-level descriptions of acid-water interactions through the study of neutral acid-water complexes. Current understanding of the nature of hydrated protons is first summarized, and a parallel discussion of structural aspects of acid-water complexes is then presented. The nature of proton transfer, and its evolution with cluster size, is described. The review concludes with several examples that lie at the intersection between fundamental work on hydrated acids and important physiochemical processes in the atmosphere.