What molecule am I?
Benzoic acid, the simplest benzene-based carboxylic acid, has been known since the 16th century. One of its discoverers was the legendary clairvoyant Nostradamus. Its most common natural source is gum benzoin, a resin found in the bark of trees of the genus Styrax.
Most benzoic acid produced today is synthetic. Its first industrial synthesis was the hydrolysis of benzotrichloride to calcium benzoate, followed by acidification. This method has been completely displaced by the air oxidation of toluene, which avoids the problem of product contamination with chlorinated byproducts.
Many processed foods contain benzoic acid or one of its salts as a preservative. The acid inhibits the growth of bacteria, molds, and yeasts; it works best when the food has an acidic pH value. Benzoic acid also is often found in topical antifungal preparations.
Why is benzoic acid our December holiday molecule? It’s the white stuff predominantly used to mimic snowflakes in snow globes. For a holiday project, you might want to create your own snow globe by using the procedures developed by Steve Spangler Science or Science with Mrs. Pittenger. Benzoic acid is readily available from Amazon and other vendors.
Benzoic acid hazard information
| Hazard class* | Hazard statement | |
|---|---|---|
| Skin corrosion/irritation, category 2 | H315—Causes skin irritation |  |
| Serious eye damage/eye irritation, category 1 | H318—Causes serious eye damage |  |
| Specific target organ toxicity (lungs), repeated exposure, category 1 | H372—Causes damage to organs (lungs) through prolonged or repeated exposure |  |
| Hazardous to the aquatic environment, acute hazard, category 3 | H402—Harmful to aquatic life | |
*Globally Harmonized System of Classification and Labeling of Chemicals.
Explanation of pictograms.
MOTW update: September 25, 2023
Benzoic acid1 is the simplest aromatic carboxylic acid and a commonly used preservative in foods and a snowflake mimic in holiday snow globes.
This past August, Yifan Meng, Richard N. Zare*, and Elumalai Gnanamani* at Stanford University (CA) and the Indian Institute of Technology Roorkee reported a catalyst-free method for producing phenol from benzoic acid. They electrosprayed ≈10-μm microdroplets of the acid dissolved in water into a chamber (e.g., a mass spectrometer port) to realize a calculated yield of ≈4.7%. The method has yet to be scaled up.
1. CAS Reg. No. 65-85-0.
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Benzoic acid fast facts
| CAS Reg. No. | 65-85-0 |
| SciFinder nomenclature | Benzoic acid |
| Empirical formula | C7H6O2 |
| Molar mass | 122.12 g/mol |
| Appearance | White crystals |
| Melting point | 122 ºC |
| Water solubility | 3.4 g/L |
Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.
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