Combined computational and experimental investigation on the Fenton reagent catalysed hydroxylation of benzene.

• A new benzene hydroxylation process was stablished by density functional theory. • The NIH shift in hydroxylation process was explicitly demonstrated. • Two intermediate products in the hydroxylation process were meticulously investigated. • One vital intermediate product in the benzene hydroxylation was confirmed. Phenol is one of the most important chemicals in industry, generally produced from benzene in cumene processes. Alternatively, the direct hydroxylation of benzene catalysed by Fenton reagent has been a potentially sustainable process for the production of phenol. Computational calculation method combined with experiments were both employed to investigate the Fenton reagent catalysed hydroxylation of benzene. Computational calculation turned out that the H migration National Institutes of Health (NIH) shift in the benzene hydroxylation reaction including intramolecular immigration and an intermolecular process. The activation energy (ΔG) for the H migration between IM2 molecules was 17.5 kcal mol⁻¹, while the ΔG for the intramolecular H transfer was 49.4 kcal mol⁻¹. The crucial intermediates in the direct hydroxylation reaction were characterised by a variety of analysis methods. There were three types of C-C bonds in IM1 with Mayer bond order (MBO) equivalent to 1.272, 1.581, and 1.041 respectively, and the C-C bonds in IM2 were not equal based on the localised orbitals and orbital composition analysis and a series of electronic structure information. Moreover, the global electron delocalisation analysis visually demonstrated an uneven distribution of π electron, revealing the aromaticity of these two intermediates. These two intermediates exhibited both aromaticity and antiaromaticity features under external magnetic conditions. Notably, the nuclear magnetic resonance results showed the existence of one of the prominent intermediates. [Display omitted] [ABSTRACT FROM AUTHOR]