Interfacial Water Structure of Binary Liquid Mixtures Reflects Nonideal Behavior

The evaporation of molecules from water–organic solute binary mixtures is key for both atmospheric and industrial processes such as aerosol formation distillation. Deviations ideal energetics can be assigned to intermolecular interactions in solution, yet occurs the interface, poorly understood interfacial, rather than bulk, structure affects kinetics. Here we determine interfacial nonideal water with methanol, ethanol, formic acid, by combining surface-specific vibrational spectroscopy molecular dynamics simulations. We find that free, dangling OH groups at interfaces these differently behaving are essentially indistinguishable. In contrast, ordering hydrogen-bonded differs substantially three interfaces. Specifically, become more disordered (ordered) methanol ethanol (formic acid), showing higher (lower) vapor pressure predicted Raoult’s law.