Vanillin
Formula
C8H8O3
IUPAC Name
3-Hydroxy-4-methoxy-benzaldehyde
Preparation
Vanillin is a well-known flavoring agent found naturally in vanilla pods. It can also be prepared synthetically. One common method is the Reimer–Tiemann reaction starting from guaiacol.
Another synthetic route:
- Brominate p-hydroxybenzaldehyde to form mono-bromo-p-hydroxybenzaldehyde.
- This compound undergoes nucleophilic substitution with sodium methoxide.
- The reaction is carried out in the presence of cuprous bromide catalyst.
Tests for Purity
1. Appearance
A 5% w/v solution of vanillin in ethanol is compared with a standard solution. The color of the test sample should not be more intense than the standard.
2. Thin-Layer Chromatography (TLC)
The test and standard samples are run in a suitable mobile phase. After spraying with an appropriate reagent, the color and intensity of spots are compared. The test sample should not have a denser coloration than the standard.
3. Sulfated Ash
Not more than 0.1%.
4. Loss on Drying
Less than 1% when dried over P2O5.
Assay
Weigh about 0.12 g of vanillin, dissolve in 20 ml ethanol, add 60 ml CO2-free water, and titrate with 0.1 M NaOH. The endpoint is detected potentiometrically.
Equivalence: 1 ml of 0.1 M NaOH ≡ 0.01521 g of vanillin (C8H8O3)
Alternatively, an acid–base titration with potentiometric detection may be used.
Uses
- Employed as an intermediate in the synthesis of pharmaceuticals and other fine chemicals.
- Widely used as a flavoring agent, especially in chocolates, ice creams, and confectionary products.
- Used in perfumes and fragrances, and to mask unpleasant odors in medicines and household products.
Detailed Notes:
For PDF style full-color notes, open the complete study material below:
PATH: PHARMD/PHARMD NOTES/ PHARMD FIRST YEAR NOTES/ ORGANIC CHEMISTRY/ PHARMACEUTICAL ORGANIC CHEMISTRY/ VANILLIN.