Origin of the selectivity in the gold-mediated oxidation of benzyl alcohol

Benzyl alcohol has received substantial attention as a probe molecule to test the selectivity and efficiency of novel metallic gold catalysts. Herein, the mechanisms of benzyl alcohol oxidation on a gold surface covered with atomic oxygen are elucidated; the results show direct correspondence to the...

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Bibliographic Details
Published in:Surface science 2012-08, Vol.606 (15-16), p.1129-1134
Main Authors: Rodríguez-Reyes, Juan Carlos F., Friend, Cynthia M., Madix, Robert J.
Format: Article
Language:English
Subjects:
Alcohols
Benzaldehyde
Benzoic acid
Benzyl alcohol
Catalysis
Catalysts
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Dehydrogenation
Esters
Exact sciences and technology
Gold
Oxidation
Physics
Selectivity
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Summary:Benzyl alcohol has received substantial attention as a probe molecule to test the selectivity and efficiency of novel metallic gold catalysts. Herein, the mechanisms of benzyl alcohol oxidation on a gold surface covered with atomic oxygen are elucidated; the results show direct correspondence to the reaction on gold-based catalysts. The selective, partial oxidation of benzyl alcohol to benzaldehyde is achieved with low oxygen surface concentrations and takes place through dehydrogenation of the alcohol to form benzaldehyde via a benzyloxy (C6H5–CH2O) intermediate. While in this case atomic oxygen plays solely a dehydrogenating role, at higher concentrations it leads to the formation of intermediates from benzaldehyde, producing benzoic acid and CO2. Facile ester (benzyl benzoate) formation also occurs at low oxygen concentrations, which indicates that benzoic acid is not a precursor of further oxidation of the ester; instead, the ester is produced by the coupling of adsorbed benzyloxy and benzaldehyde. Key to the high selectivity seen at low oxygen concentrations is the fact that the production of the aldehyde (and esters) is kinetically favored over the production of benzoic acid. ► The mechanism of the oxidation of benzyl alcohol on metallic gold is revealed. ► Selectivity for aldehyde and ester is high at low surface oxygen coverage. ► Aldehyde/ester formation is kinetically more facile than formation of benzoic acid.
ISSN:0039-6028
1879-2758
DOI:10.1016/j.susc.2012.03.013