Exploring The Solvation Of Acetic Acid In Water Using Liquid Jet X-Ray Photoelectron Spectroscopy And Core Level Electron Binding Energy Calculations

Liquid jet X-ray photoelectron spectroscopy was used to investigate changes in the local electronic structure of acetic acid in the bulk of aqueous solutions induced by solvation effects. These effects manifest themselves as shifts in the difference in the carbon is binding energy (Delta BE) between the methyl and carboxyl carbons of acetic acid. Furthermore, molecular dynamics simulations, coupled with correlated electronic structure calculations of the first solvation sphere, provide insight into the number of water molecules directly interacting with the carboxyl group that are required to match the Delta BE from the photoelectron spectroscopy experiments. This comparison shows that a single water molecule in the first solvation shell describes the photo-electron Delta BE of acetic acid while at least 20 water molecules are required for the conjugate base, acetate, in aqueous solutions.