Improvement of product selectivity is a major concern of the day. Presence of a coreactant can alter the rate as well as product selectivity of many key reactions like Friedel-Crafts benzylation. Single pot benzylation of o-xylene with benzyl chloride and benzyl alcohol was studied over transition metal exchanged pillared clay catalysts. Complete conversion of benzyl alcohol occured within one hour with 100% monoalkylated product selectivity. The reaction of o-xylene with benzyl alcohol was found to proceed fast in presence of benzyl chloride in single pot, than when present alone as the benzylating species. This enhancement occurs at the expense of no reaction of benzyl chloride, which when present alone reacts faster than benzyl alcohol. Existence of a second transition metal exchanged between the pillars increased the rate of the reaction. A detailed investigation of the reaction variables suggested preferential adsorption of benzyl alcohol to catalyst active sites as the reason.
References Yan, Y., Zhou, L. & Zhang, Y. (2008). Synthesis of MgO hierarchical nanostructures controlled by the supersaturation ratio, J. Phys. Chem. 112, 19831-19835. DOI: 10.1021/ jp806639x. Choudhary, V. R. & Dumbre, D. K. (2009). Magnesium oxide supported nano-gold: A highly active catalyst for solvent-free oxidation of benzylalcohol to benzaldehyde by TBHP, Catal. Communications 10, 1738-1742. DOI: 10.1016/ j.catcom.2009.05.020. Ouraipryvan, P., Sreethawong, T. & Chavadej, S. (2009). Synthesis of crystalline MgO nanoparticle with mesoporous
of 2,5-diformylfuran and furan-2,5-dicarboxylic acid by catalytic air-oxidation of 5-hydroxymethylfurfural. Unexpectedly selective aerobic oxidation of benzylalcohol to benzaldehyde with metal=bromide catalysts. Adv. Synth. Catal. 343, 102-111. DOI: 10.1002/1615-4169(20010129)343:1<102::AID-ADSC102>3.0.CO;2-Q. 23. Saha, B., Dutta, S. & Abu-Omar, M.M. (2012). Aerobic oxidation of 5-hydroxylmethylfurfural with homogeneous and nanoparticulate catalysts. Catal. Sci. Technol. 2, 79-81. DOI: 10.1039/c1cy00321f. 24. Miura, T., Kakinuma, H., Kawano, T. & Matsuhisa, H