Compounds · Aldehydes · Terpenoid pathway
Citronellal
Also known as Rhodinal — an analysis may use any of these names
Green, slightly metallic, almost soapy. On its own it builds most of the smell of kaffir lime leaf.
- CAS
- 106-23-0
- Formula
- C10H18O
- Molar mass
- 154.25
- Odour threshold
- 10 ppbin water
- Boiling point
- ≈ 207 °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: Terpenoid pathway — plants build them from identical five-carbon blocks.
About the threshold figure
Moderately low. This is the main compound of kaffir lime leaf and Java citronella.
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 ten-carbon aldehyde; its carbonyl group is moderately polar, so it sits in the middle of the band, just after linalool.
Where else you meet it
Kaffir lime leaf, Java citronella, lemon-scented gum. A raw material for industrial synthesis of citronellol and menthol.