Compounds · Monoterpenes · Terpenoid pathway
p-Cymene
Dry, light wood, with a slight solvent note. Fainter than most other monoterpenes and without any freshness.
- CAS
- 99-87-6
- Formula
- C10H14
- Molar mass
- 134.22
- Odour threshold
- 11 ppbin water
- Boiling point
- ≈ 177 °C at atmospheric pressure
The two axes are 39 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: Terpenoid pathway — plants build them from identical five-carbon blocks.
About the threshold figure
Moderately low. Much lower than limonene although both are monoterpenes — the aromatic ring makes the difference.
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
The only monoterpene in this group with an aromatic ring, so it is much more stable than the open-chain terpenes. That is also why it builds up in oils kept for a long time: many other terpenes oxidise into it.
Where else you meet it
Present in almost every essential oil, usually at a few per cent. An unusually high share of p-cymene is a sign that an oil is old or has been heat-treated.