Effect of Li on the catalytic activity of MgO for the synthesis of flavanone

We have investigated the effects of Li on the structure, surface basicity and catalytic activity of MgO for the synthesis of flavanone. Introduction of low amounts of Li (i.e., ≤0.1 wt.%) was found to promote the rate of the Claisen–Schmidt condensation reaction, which is the first step in this process. However, at Li loadings above 0.1 wt.% a detrimental effect was observed, due to a concomitant decrease in surface area and increase in MgO crystallite size. A strong correlation was observed between surface-normalized basicity and catalytic activity. The increase in activity at higher levels of surface basicity can be attributed to the increased ability of Li–O− pairs to abstract a proton from the 2′-hydroxyacetophenone reactant, thus facilitating the adsorption and subsequent surface reactions of this molecule.

Figure optionsDownload high-quality image (202 K)Download as PowerPoint slideResearch highlights▶ MgO undergoes structural modification upon addition of Li. ▶ Above 0.1 wt.% Li substantial decrease in surface area is observed. ▶ Good correlation of MgO surface basicity and rate for Claisen–Schmidt condensation. ▶ Ability of Li–O− to abstract proton from 2′-hydroxyacetophenone is the key step.