Gold Helps Green Up Alcohol Oxidations

By immobilizing gold nanoparticles on specific metal oxide nanoparticles, chemists in Japan have devised a method to selectively convert poorly reactive long-chain alcohols to carboxylic acids or alkyl esters while also minimizing waste. The strategy, developed by Tamao Ishida of Kyushu University, Masatake Haruta of Tokyo Metropolitan University, and coworkers, could lead to greener industrial production of high-value acids and esters used as surfactants and lubricants (ChemSusChem, DOI: 10.1002/cssc.201200324). Building on their earlier work with methanol and ethanol, the researchers found that gold nanoparticles supported on nickel oxide selectively catalyze oxidation of 1-octanol to octanoic acid. In addition, gold nanoparticles supported on cerium oxide selectively yield octyl octanoate. The reactions use O₂ as the oxidant, rather than a stoichiometric oxidizing reagent. They also work in neutral aqueous conditions. Alcohol oxidations usually require basic conditions to generate carboxylic acids or esters, the researchers explain. In the absence of base, aldehydes are generated. However, carboxylates formed in basic solution must be neutralized with a strong acid, which adds cost and generates a large amount of inorganic salt that must be treated as waste. The new method avoids that problem.