Anions Dramatically Enhance Proton Transfer across
Fundamental processes in chemistry and biology are driven by proton transfer (PT) across water interfaces with hydrophobic media. However, what distinguishes PT ‘on water’ from conventional PT ‘in water’ remains unclear. Here we show that PT from gaseous nitric acid to liquid water is dramatically accelerated by non‐specific anions. We found that HNO3(g) fails to dissociate on pure water surfaces but is fully deprotonated on 1 mM electrolytes. Quantum mechanical (QM) calculations confirm that HNO3(g) dissociation on pure water is unfavorable and show that anions pre‐organize interfacial water, thereby setting the stage for adiabatic PT. Our findings provide direct evidence of the critical role electrostatic pre‐organization plays in catalyzing proton transfers across water‐hydrophobe interfaces, such as those involved in cloud acidification and enzymatic events.
Download animation of reaction coordinate at transition state with chloride (.mov): Cl movie
Download animation of reaction coordinate at transition state without chloride (.mov): No Cl movie
Personnel and collaborators: Himanshu Mishra, Shinichi Enami, Dr. A. J. Colussi, Prof. M. Hoffmann, Dr. Robert Nielsen
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