Ab initio metadynamics calculations reveal complex interfacial effects in acetic acid deprotonation dynamics

• DOI: 10.1016/j.molliq.2021.115624
• Publication Date: 2021-02-11T01:46:46Z
• Authors: Sohag Biswas; Bryan M. Wong
• Keywords: 01 natural sciences; 0104 chemical sciences

Acid-base reactions play a central role in solution chemistry, with carboxylic acids being particularly important in atmospheric chemical processes. In this work, we harness metadynamics calculations with Born-Oppenheimer molecular dynamics (BOMD) simulations to understand deprotonation dynamics of acetic acid (CH3COOH) in both bulk and air-water interfacial environments. Collective variables are carefully chosen in our well-tempered metadynamics simulations to capture the deprotonation process in various aqueous configurations. Our findings show that the free energy barrier for deprotonation of acetic acid at the air-water interface is lower than in the bulk, in accordance with the available experimental data. Furthermore, our well-tempered metadynamics calculations suggest that the variations in free energy are primarily due to intricate solvation shell effects.