Green synthesis of vanillyl mandelic acid (sodium salt) from guaiacol and sodium glyoxylate over novel silica encapsulated magnesium hydroxide

Abstract

Vanillyl mandelic acid (VMA) is an intermediate in the synthesis of vanillin and is an end-stage metabolite. In the present work, VMA (sodium salt) was selectively synthesized from guaiacol and sodium glyoxylate which can be sourced from biomass valorization. Different catalysts were prepared; out of which silica encapsulated magnesium hydroxide (SEMH) was active, selective, and reusable. Vanillyl mandelic acid (sodium salt) was efficiently obtained with 70% selectivity at guaiacol conversion of 55% over SEMH at 100 °C after 5 h. VMA could be obtained from the sodium salt. The Langmuir–Hinshelwood–Hougen–Watson (LHHW) model with weak adsorption of all species was found to describe the kinetics. The apparent activation energy for formation of vanillyl mandelic acid was 21.1 kcal mol^-1.