Evidence of Photoacidic Characteristics by Nitrophenols in Organic Matrices

AVERY DALTON, Dmitry Fishman, Sergey Nizkorodov, University of California, Irvine

     Abstract Number: 45
     Working Group: Aerosol Chemistry

Abstract
The condensed phase photochemistry of nitrophenols has been the subject of much scientific inquiry, revealing ambient photodegradation lifetimes on the order of days to weeks depending on the matrix encapsulating the nitrophenol. Despite such investigations, the mechanisms through which these molecules degrade, particularly para-nitrophenols, are still largely ambiguous. Considering the relatively low volatility of these molecules it becomes important to have a detailed understanding of their photochemistry in the atmosphere. This work aims to investigate the ultrafast photochemical dynamics of 4-nitrocatechol (4NC), a strong chromophore which has been used in laboratory studies as a proxy for brown carbon. 4NC exhibits “push-pull” characteristics which could strengthen its potential to act as a photoacid. The effects of aqueous and organic solvents are examined and reveal implications toward environmental degradation of nitrophenols. Preliminary results indicate that 4NC may be capable of excited-state proton transfer on ultrafast timescales, even in a weakly-protic solvent 2-propanol. Though nitrophenols are often expected to react via excited triplet states, this work supports other recent findings that suggest more consideration should be put toward the role of the anions of these molecules in their overall photodegradation in cloud water and organic aerosol particles.