Chemical Equilibrium Probed by Two-Dimensional IR Spectroscopy: Hydrogen Bond Dynamics of Methyl Acetate in Water

The solvation dynamics of methyl acetate in heavy water are analyzed by means of two-dimensional infrared spectroscopy, in conjunction with Car-Parrinello molecular dynamics simulations. The C=O stretching infrared band of methyl acetate in water splits into a doublet as a consequence of the hydrogen bond interaction with the solvent, which leads to the equilibrium between two solvated species, consisting of one methyl acetate molecule bonded to one and two water molecules. The structure and dynamics of the water molecules bound to methyl acetate are characterized by means of experiments and simulations, allowing an accurate description of the kinetics of the exchange process and the lifetime of the hydrogen bond.