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Chemphyschem

Title:		Isoprene Reactivity on Water Surfaces from ab initio QM/MM Molecular Dynamics Simulations
Author(s):		Martins-Costa MTC; Ruiz-Lopez MF;
Address:		"Laboratoire de Physique et Chimie Theoriques, UMR CNRS 7019, University of Lorraine, CNRS, BP 70239, 54506, Vandoeuvre-les-Nancy, France"
Journal Title:		Chemphyschem
Year:		2020
Volume:		20200921
Issue:		20
Page Number:		2263 - 2271
DOI:		10.1002/cphc.202000652
ISSN/ISBN:		1439-7641 (Electronic) 1439-4235 (Linking)
Abstract:		"Isoprene is the most abundant volatile organic compound in the atmosphere after methane. While gas-phase processes have been widely studied, the chemistry of isoprene in aqueous environments is less well known. Nevertheless, some experiments have reported unexpected reactivity at the air-water interface. In this work, we have carried out combined quantum-classical molecular dynamics simulations of isoprene at the air-water interface, as well as ab initio and density functional theory calculations on isoprene-water complexes. We report the first calculation of the thermodynamics of adsorption of isoprene at the water surface, examine how hydration influences its electronic properties and reactivity indices, and estimate the OH-initiated oxidation rate. Our study indicates that isoprene interacts with the water surface mainly through H-pi bonding. This primary interaction mode produces strong fluctuations of the pi and pi(*) bond stabilities, and therefore of isoprene's chemical potential, nucleophilicity and ionization potential, anticipating significant dynamical effects on its reactivity at the air-water interface. Using data from the literature and free energies reported in our work, we have estimated the rate of the OH-initiated oxidation process at the air-water interface (5.0x10(12) molecule cm(-3) s(-1) ) to be about 7 orders of magnitude larger than the corresponding rate in the gas phase (8.2x10(5) molecule cm(-3) s(-1) ). Atmospheric implications of this result are discussed"
Keywords:		Isoprene OH oxidation QM/MM Molecular Dynamics simulations air-water interface on-water catalysis;
Notes:		"PubMed-not-MEDLINEMartins-Costa, Marilia T C Ruiz-Lopez, Manuel F eng LCT2550/French CINES/International Research Support, Non-U.S. Gov't Germany 2020/08/20 Chemphyschem. 2020 Oct 16; 21(20):2263-2271. doi: 10.1002/cphc.202000652. Epub 2020 Sep 21"