Compounds · Phenols · Heat (Maillard reaction and pyrolysis)
Phenol
Also known as Carbolic acid · Acid phenic — an analysis may use any of these names
Antiseptic, asphalt, with a slight note of printing ink. Sharp and dry.
- CAS
- 108-95-2
- Formula
- C6H6O
- Molar mass
- 94.11
- Odour threshold
- 5.9 ppmin water
- Boiling point
- ≈ 182 °C at atmospheric pressure
The two axes are 64 points apart. Volatility tells you whether the compound leaves a surface early or late; the threshold tells you how much of it the nose needs before it notices. When the two sit this far apart, they explain things the percentages on an analysis cannot explain on their own.
Where it comes from
Biosynthetic pathway: Heat (Maillard reaction and pyrolysis) — fire breaks large molecules into ones you can smell.
About the threshold figure
High. It needs a large concentration, and at that level it is already irritating.
Published thresholds differ by several orders of magnitude, because of differences in measuring method, sample purity and panel. The figure here is an order of magnitude for relative comparison, not a measurement. We give it only for compounds where the literature broadly agrees — 52 of the 106 compounds in the library. The rest are left blank rather than guessed.
Why it sits where it does
An aromatic ring with one hydroxyl group, forming strong hydrogen bonds, so it boils much higher than benzene of the same size.
Where else you meet it
Wood smoke, asphalt, and some island whiskies.
Regulatory note
Corrosive in pure form; in essential oils it is present only in trace amounts. This is a labelling requirement, not a warning about the product.