Compounds · Ketones · Fatty acid derivatives
1-Octen-3-one
Also known as Vinyl amyl ketone — an analysis may use any of these names
Metallic, fishy, close to blood. Very strong at extremely low concentration.
- CAS
- 4312-99-6
- Formula
- C8H14O
- Molar mass
- 126.20
- Odour threshold
- 0.005 ppbin water
- Boiling point
- ≈ 175 °C at atmospheric pressure
For this compound the two axes sit close together. Volatility tells you whether it leaves a surface early or late; the threshold tells you how much of it the nose needs before it notices.
Where it comes from
Biosynthetic pathway: Fatty acid derivatives — enzymes cut fat chains into fragments you can smell.
About the threshold figure
Extremely low, which is why a tiny amount of iron ions on the skin is enough for a clear metallic smell.
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 eight-carbon ketone with a double bond conjugated right next to the carbonyl group. Its detection threshold is among the lowest the human nose can pick up — about two hundred times lower than 1-octen-3-ol.
Something is worth noticing when you set it beside 1-octen-3-ol: the two both boil at about 175 degrees. Normally an alcohol boils higher than a ketone with the same skeleton, and two other pairs in this library follow that rule — 3-octanol eight degrees above 3-octanone, borneol nine degrees above camphor.
This pair does not, and the reason lies in conjugation. The double bond sitting right beside the carbonyl group makes the molecule flatter and more stable, and that pulls the boiling point up almost as much as the hydroxyl group gives the alcohol. Two different effects, almost the same result.
Where else you meet it
Formed when iron ions come into contact with fats on the skin. This is the molecule behind what everyone calls the smell of metal and of blood.
Dictionary entries that mention this compound
About the boiling-point figure
Cross-checked in August 2026: 174–182 °C at atmospheric pressure. Note that many sources give 56–60 °C — that value is measured at 16 mmHg, not at atmospheric pressure. Why this detail matters