The mechanism of phenol formation in the Dow Phenol Process

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 1999-10, Vol.146 (1), p.237-246
• Main Author: Buijs, W
• Format: Article
• Language: English
• Subjects: Catalysis; Catalytic reactions; Chemistry; Dow Phenol Process; Exact sciences and technology; General and physical chemistry; Phenol formation; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Toluene
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/S1381-1169(99)00236-8

The Dow Phenol Process utilises toluene as feedstock. In two separate steps, toluene is first oxidised to benzoic acid; thereafter benzoic acid is converted to phenol, using copper benzoate as the principal catalyst. The latter reaction, extensively described by Kaeding, is the so-called Dow Phenol reaction. Recent work at DSM Research showed remarkable differences in product distribution, kinetics, and influences of solvent and cocatalyst. The accepted mechanism of the Dow Phenol reaction described it as two separate single electron transfers by a pair of Cu(II) ions in a radical cage process with regiochemistry control via a flat six-membered ring. Based on all available data, however, the reaction could be better described as an electrophilic aromatic substitution on benzoic acid or benzoate as substrate, and the benzoyloxy cation as electrophile. The electrophile most likely originates from the thermal decomposition of the typical paddlewheel structure of a dinuclear Cu(II) carboxylate.