Computations of Chemical Reactions and Dynamics
Quantum chemical insights into the dissociation of nitric acid on the surface of aqueous electrolytes
Article first published online: 31 MAY 2012
Copyright © 2012 Wiley Periodicals, Inc.
International Journal of Quantum Chemistry
Special Issue: Seventh Congress of the International Society for Theoretical Chemical Physics
Volume 113, Issue 4, pages 413–417, 15 February 2013
How to Cite
Mishra, H., Nielsen, R. J., Enami, S., Hoffmann, M. R., Colussi, A. J. and Goddard, W. A. (2013), Quantum chemical insights into the dissociation of nitric acid on the surface of aqueous electrolytes. Int. J. Quantum Chem., 113: 413–417. doi: 10.1002/qua.24151
- Issue published online: 22 JAN 2013
- Article first published online: 31 MAY 2012
- Manuscript Accepted: 9 APR 2012
- Manuscript Revised: 6 APR 2012
- Manuscript Received: 15 JAN 2012
- National Science Foundation. Grant Number: AGS-964842.
- nitric acid dissociation;
- proton transfers at aqueous interfaces;
- electrostatic preorganization;
- interfacial anions;
- air–water interface
Recent experiments in our laboratory have shown that the probability of gaseous HNO3 deprotonation on the surface of water is dramatically enhanced by anions. Herein, we report a quantum chemical study of how a HNO3 molecule transfers its proton upon approaching water clusters containing or not a chloride ion. We find that HNO3 always binds to the outermost water molecules both via donating and accepting hydrogen-bonds, but the free energy barrier for subsequent proton transfer into the clusters is greatly reduced in the presence of Cl−. As the dissociation of HNO3 embedded in water clusters is barrierless, we infer that interfacial proton transfer to water is hindered by the cost of creating a cavity for NO3−. Our findings suggest that nearby anions catalyze HNO3 dissociation by preorganizing interfacial water and drawing the proton—away from the incipient [H+---NO3−] close ion-pairs generated at the interface. This catalytic mechanism would operate in the 1 mM Cl− range (1 Cl− in ∼5.5 × 104 water molecules) covered by our experiments if weakly adsorbed HNO3 were able to explore extended surface domains before desorbing or diffusing (undissociated) into bulk water. © 2012 Wiley Periodicals, Inc.