Vanillin

Synthesis route :

Vanillin is mainly synthesized from lignin or Guaiacol. Since these processes result in 160 kg of waste per kg of finished product, the synthesis of vanillin tends to be replaced by biosynthetic pathways, from rice bran, natural curcumin or natural Eugenol. The synthesis from lignin is made by an alklaine treatment at high temperature and pressure with oxidants. Vanillin is separated from the other compounds obtained by extraction, distillation and crystallization. Another synthetic route starts from Guaiacol, synthesized from Catechol. Guaiacol condenses to glyoxylic acid in a alklaine medium and at room temperature. Vanillin is obtained by acidification and decarboxylation of the reaction mixture. Another similar process uses Guaiacol and formaldehyde, to obtain the ortho and para-vanillic alcohols. Then, a catalytic oxidation (with palladium and bismuth) allows to obtain Vanillin, separated from the other reaction products by crystallization. Using an excess of formaldehyde involves an oxidation and decarboxylation step, always to obtain Vanillin as the final product. Nowadays, several production processes using biochemistry consist in a bioconversion of ferulic acid, Isoeugenol or Eugenol, using bacteria, fungi and plant cells capable of transforming these compounds.

Synthesis precursor :

Vanillin is a precursor to the synthesis of several compounds of olfactory interest. Addition reactions can be carried out on its aromatic ring. A catalytic hydrogenation allows to synthesize Vanillic Alcohol. Several esterifications are possible by exploiting the alcohol function of the molecule (as in the synthesis of Isobutavan®), as well as aldol condensation by exploiting the aldehyde function.

Isomerism :

Vanillin is a constitutional isomer of Methyl Salicylate. Although close structurally, Methyl Salicylate has a much fruitier, more floral and powerful smell than Vanillin.