Uv Photolysis Study Of Para-aminobenzoic Acid Using Parahydrogen Matrix Isolated Spectroscopy

McKinnon, Alexandra

Permalink

https://hdl.handle.net/2142/116627 Copy

Description

Title

Uv Photolysis Study Of Para-aminobenzoic Acid Using Parahydrogen Matrix Isolated Spectroscopy

Author(s)

McKinnon, Alexandra

Contributor(s)

• Momose, Takamasa
• Djuricanin, Pavle
• Moore, Brendan

Issue Date

2022-06-21

Keyword(s)

Photodissociation and photochemistry

Abstract

\emph{Para}-aminobenzoic acid (PABA) is one of the original sunscreen chemical agents. As these agents often undergo photodissociation during the process of UV absorption, understanding the photochemical behaviour of sunscreen agents is highly important. In this study, the photolysis of PABA was studied at three different UV ranges (UVA: 355 nm, UVB: $>$280 nm, and UVC: 266 nm and 213 nm) using parahydrogen (\emph{p}H$_{2}$) matrix isolation Fourier-Transform infrared (FTIR) spectroscopy. Parahydrogen has weak cage effects that allow radicals to escape the lattice site and therefore prevent further radical recombination reactions. PABA was found to be stable under UVA irradiation. However, PABA dissociated into 4-aminylbenzoic acid (the PABA radical) through amino hydrogen atom loss under UVB and UVC irradiation.$^{1}$ The production of the PABA radical supports a previously proposed mechanism of the formation of the carcinogenic PABA-thymine adduct. The infrared spectrum of the PABA radical was analyzed with quantum chemical calculations. Two conformers of this radical were observed in the \emph{p}H$_{2}$ matrix. Both conformers of the PABA radical were stable in solid \emph{p}H$_{2}$ for hours after irradiation. This work displays that \emph{p}H$_{2}$ matrix isolation spectroscopy is effective for sunscreen agent photochemical studies. \newline \newline 1. McKinnon, A.; Moore, B.; Djuricanin, P.; Momose, T. UV Photolysis Study of \emph{Para}-Aminobenzoic Acid Using Parahydrogen Matrix Isolated Spectroscopy. \emph{Photochem.} \textbf{2022,} \emph{2,} 88 – 101.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116627

DOI

https://doi.org/10.15278/isms.2022.TJ09

Copyright and License Information

Copyright 2022 held by the authors

Owning Collections