Compounds · Ketones · Terpenoid pathway
Nootkatone
Also known as Nootkaton — an analysis may use any of these names
Grapefruit peel in concentrated form, bitter and warm. Very lasting, hardly evaporating.
- CAS
- 4674-50-4
- Formula
- C15H22O
- Molar mass
- 218.33
- Odour threshold
- 1 ppbin water
- Boiling point
- ≈ 290 °C estimated
The two axes are 53 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
Low. Nootkatone makes up a very small share of grapefruit peel but decides its characteristic note.
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
A fifteen-carbon sesquiterpene ketone with a carbonyl group, so it is both heavy and polar. It sits at the far right of the band — a surprise for a smell that belongs to the citrus family.
Where else you meet it
Grapefruit peel is the main source. Its detection threshold is very low, so a small amount is enough to recognise.
Dictionary entries that mention this compound
About the boiling-point figure
Not cross-checked. A common source gives 170 °C and one supplier gives 125 °C at 0.5 mmHg — the two figures cannot both be right at atmospheric pressure. The value we use is an estimate based on structure. Why this detail matters