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Synthesis of vanillin and 4‐hydroxybenzaldehyde by a reaction scheme involving condensation of phenols with glyoxylic acid
Author(s) -
Kalikar Rajendra G.,
Deshpande Ramesh S.,
Chandalia Sampatraj B.
Publication year - 1986
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.280360107
Subject(s) - glyoxylic acid , mandelic acid , vanillin , chemistry , guaiacol , phenol , condensation reaction , catechol , aqueous solution , organic chemistry , phenols , nuclear chemistry , catalysis
Synthesis of vanillin and 4‐hydroxybenzaldehyde from guaiacol and phenol, respectively, was investigated. The condensation of guaiacol and phenol with glyoxylic acid in an aqueous alkaline medium resulted in the formation of 3‐methoxy‐4‐hydroxymandelic and 4‐hydroxymandelic acid respectively. A process version for the condensation of the phenol with glyoxylic acid, wherein it was found advisable to add an aqueous solution of glyoxylic acid and part of alkali to a batch of the phenol in aqueous alkali, was found to give 77% yield of the mandelic acid based on glyoxylic acid. The oxidation of the mandelic acid could be more suitably carried out at 95°C using 0.51 mol of copper (II) hydroxide for every mole of the mandelic acid in a process where air is simultaneously passed. Taking 3‐methoxy‐4‐hydroxymandelic acid as an example, 88% conversion to vanillin could be obtained. The reaction was found to be second order with respect to the mandelic acid.