VANILLIN PRODUCTION preparation from guaiacol

Production. Commercial vanillin is obtained by processing waste sulfite liquors or is synthesized from guaiacol. Preparation by oxidation of isoeugenol is of historical interest only. 

Preparation from Waste Sulfite Liquors. The starting material for vanillin production can also be the lignin present in sulfite wastes from the cellulose industry. The concentrated mother liquors are treated with alkali at elevated temperature and pressure in the presence of oxidants. The vanillin formed is separated from the by-products, particularly ace-tovanillone. 4-hydroxy-3-methoxyacetophenone, by extraction, distillation, and crystallization. In contrast to vanillin from lignin, the principal impurity found in vanillin from guaiacol is 5-methyl vanillin, typically present at levels of about 100 ppm, although levels as high as 3000 ppm have been found. This impurity is completely odorless. 

During the first half of the nineteenth century, the importance of the single odorous chemicals contained in natural products was recognized, and efforts were devoted to their isolation and characterization. Soon after, their synthesis was carried out by chemical methods. Cinnamaldehyde was first isolated in 1834 and then synthesized in 1856 by Chiozza [2]. In 1874, Hemann and Haarmann deduced the chemical structure of vanillin, and found a synthesis from coniferin, a glucoside of isoeugenol found in pine bark [3]. In 1876, Reimer prepared vanillin from guaiacol [4, 5]. 

Guyot and Gey have prepared vanUlin by a synthesis depending on the property possessed by compounds containing t-wo carbonyl groups in juxtaposition, of condensing with guaiacol giving products from which it is easy to pass to vanillin. 

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