Reaction of Aniline with Singlet Oxygen (O21Δg)

Jomana Al-Nu'Airat, Mohammednoor Altarawneh, Xiangpeng Gao, Phillip R. Westmoreland, Bogdan Z. Dlugogorski

Research output: Contribution to journalArticle

Abstract

Dissolved organic matter (DOM) acts as an effective photochemical sensitizer that produces the singlet delta state of molecular oxygen (O21Δg), a powerful oxidizer that removes aniline from aqueous solutions. However, the exact mode of this reaction, the p- to o-iminobenzoquinone ratio, and the selectivity of one over the other remain largely speculative. This contribution resolves these uncertainties. We report, for the first time, a comprehensive mechanistic and kinetic account of the oxidation of aniline with the singlet delta oxygen using B3LYP and M06 functionals in both gas and aqueous phases. Reaction mechanisms have been mapped out at E, H, and G scales. The 1,4-cycloaddition of O21Δg to aniline forms a 1,4-peroxide intermediate (M1), which isomerizes via a closed-shell mechanism to generate a p-iminobenzoquinone molecule. On the other hand, the O21Δg ene-type reaction forms an o-iminobenzoquinone product when the hydroperoxyl bond breaks, splitting hydroxyl from the 1,2-hydroperoxide (M3) moiety. The gas-phase model predicts the formation of both p- and o-iminobenzoquinones. In the latter model, the M1 adduct displays the selectivity of up to 96%. A water-solvation model predicts that M1 decomposes further, forming only p-iminobenzoquinone with a rate constant of k = 1.85 × 109 (L/(mol s)) at T = 313 K. These results corroborate the recent experimental findings of product concentration profile in which p-iminobenzoquinonine represents the only detected product.

Original languageEnglish
Pages (from-to)3199-3206
Number of pages8
JournalJournal of Physical Chemistry A
Volume121
Issue number17
Early online date13 Apr 2017
DOIs
Publication statusPublished - 4 May 2017
Externally publishedYes

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  • Cite this

    Al-Nu'Airat, J., Altarawneh, M., Gao, X., Westmoreland, P. R., & Dlugogorski, B. Z. (2017). Reaction of Aniline with Singlet Oxygen (O21Δg). Journal of Physical Chemistry A, 121(17), 3199-3206. https://doi.org/10.1021/acs.jpca.7b00765