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Degradation Mechanism of Benzo[a]pyrene Initiated by the OH Radical and 1O2: An Insight from Density Functional Theory Calculations.

ABSTRACT: The degradation mechanism of benzo[a]pyrene (BaP) initiated by •OH and 1O2 in aqueous solution is investigated by density functional theory calculations. The main degradation products are BaP-1,6-quinone, BaP-3,6-quinone, BaP-4,6-quinone, and BaP-6,12-quinone. •OH and HO2 are the main intermediate radical species. At a low initial concentration of •OH, 1O2 could be a primary driver for BaP degradation. The degradation mechanism includes six consecutive elementary reactions: (1) 1O2 initiation forming BaP-6-OO. (2) 1,3 H-shift (H atom shifts to the OO group) that is promoted by H2O, forming BaP-6-OOH. (3) BaP-6-OOH decomposes into the •OH radical and BaP-6-O. (4) •OH addition to BaP-6-O forming BaP-6-O-1(3,4,12)-OH. (5) Extracting the H atom from the carbon with the OH group by 1O2. (6) Extracting the H atom from the OH group by HO2. At a high initial concentration of •OH, the •OH-initiated and 1O2-initiated degradation reactions of BaP are both feasible. The degradation mechanism includes six consecutive elementary reactions: (1) •OH initiation forming BaP-6-OH or 1O2 initiation forming BaP-6-OO. (2) 1O2 addition to BaP-6-OH forming BaP-6-OH-12(1,3,4)-OO or •OH addition to BaP-6-OO forming BaP-6-OO-12(1,3,4)-OH. (3) Extracting the H atom from the carbon with the OH group by 1O2, forming HO2. (4) 1,3 H-shift (H-shift from the carbon to the OO group), promoted by H2O. (5) The loss of the OH radical. (6) Abstracting the H atom from the OH group by HO2. In this paper, the formation of BaP-4,6-quinone via the BaP degradation is first reported. Water participates in the elementary reaction in which the H atom attached on the aromatic ring shifts to the OO group, serving as a bridge that stabilizes the transition state and transports the proton. A comprehensive investigation explains the degradation mechanism of BaP initiated by •OH and 1O2 in aqueous solution.

SUBMITTER: Chen XM

PROVIDER: S-EPMC7557245 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Degradation Mechanism of Benzo[a]pyrene Initiated by the OH Radical and 1O2: An Insight from Density Functional Theory Calculations.

Chen Xue-Mei XM Chu Yun-Jie YJ Liu Chun-Guang CG

ACS omega 20200928 40

The degradation mechanism of benzo[a]pyrene (BaP) initiated by •OH and 1O2 in aqueous solution is investigated by density functional theory calculations. The main degradation products are BaP-1,6-quinone, BaP-3,6-quinone, BaP-4,6-quinone, and BaP-6,12-quinone. •OH and HO2 are the main intermediate radical species. At a low initial concentration of •OH, 1O2 could be a primary driver for BaP degradation. ...[more]

PMID: 33073081

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Dataset Information

Degradation Mechanism of Benzo[a]pyrene Initiated by the OH Radical and 1O2: An Insight from Density Functional Theory Calculations.

Publications

Degradation Mechanism of Benzo[<i>a</i>]pyrene Initiated by the OH Radical and <sup>1</sup>O<sub>2</sub>: An Insight from Density Functional Theory Calculations.

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