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Hussein AA, Al-Hadedi AAM, Mahrath AJ, Moustafa GAI, Almalki FA, Alqahtani A, Shityakov S, Algazally ME. Mechanistic investigations on Pinnick oxidation: a density functional theory study. R Soc Open Sci 2020; 7:191568. [PMID: 32257322 PMCID: PMC7062072 DOI: 10.1098/rsos.191568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Accepted: 01/13/2020] [Indexed: 05/04/2023]
Abstract
A computational study on Pinnick oxidation of aldehydes into carboxylic acids using density functional theory (DFT) calculations has been evaluated with the (SMD)-M06-2X/aug-pVDZ level of theory, leading to an important understanding of the reaction mechanism that agrees with the experimental observations and explaining the substantial role of acid in driving the reaction. The DFT results elucidated that the first reaction step (FRS) proceeds in a manner where chlorous acid reacts with the aldehyde group through a distorted six-membered ring transition state to give a hydroxyallyl chlorite intermediate that undergoes a pericyclic fragmentation to release the carboxylic acid as a second reaction step (SRS). 1H NMR experiments and simulations showed that hydrogen bonding between carbonyl and t-butanol is unlikely to occur. Additionally, it was found that the FRS is a rate-determining and thermoneutral step, whereas SRS is highly exergonic with a low energetic barrier due to the Cl(III) → Cl(II) reduction. Frontier molecular orbital analysis, intrinsic reaction coordinate, molecular dynamics and distortion/interaction analysis further supported the proposed mechanism.
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Affiliation(s)
- Aqeel A. Hussein
- Faculty of Dentistry, University of Al-Ameed, Karbala PO Box 198, Iraq
- Department of Chemistry, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
| | | | - Alaa J. Mahrath
- Department of Chemistry and Biochemistry, College of Medicine, University of Babylon, Babylon, Iraq
| | - Gamal A. I. Moustafa
- Department of Chemistry, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
- Department of Medicinal Chemistry, Faculty of Pharmacy, Minia University, Minia 61519, Egypt
| | - Faisal A. Almalki
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Alaa Alqahtani
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Umm Al-Qura University, Makkah 21955, Saudi Arabia
| | - Sergey Shityakov
- Department of Anesthesia and Critical Care, University of Würzburg, 97080 Würzburg, Germany
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