16 compounds of this family in the library, boiling between 3 and 253 °C. How the family spreads along the axis says something about its shared behaviour. Left of the dashed line are compounds lighter than any essential-oil component — they are gone before the main axis begins.
Structure
Compounds that do not fit neatly into the nine families above: sulphur compounds, nitrogen compounds, free acids and rare chemical skeletons.
Behaviour on a smelling strip
No shared behaviour. The only thing in common is that many compounds in this group have extremely low detection thresholds, so they often decide the character of a smell even at a few parts in ten thousand.
Compounds in this family
Ordered by rising boiling point — which is also the order in which you smell them.
| Compound | CAS | Boiling point | Description |
|---|---|---|---|
| Trimethylamine | 75-50-3 | 3 °C | Fishy, a light ammonia. In good fish sauce it is just one note; in spoiled fish sauce it is everything. |
| Dimethyl sulfide | 75-18-3 | 37 °C | Boiled cabbage, sea, slightly fishy. At very low concentration it gives the sweet note of boiled corn. |
| Acetic acid | 64-19-7 | 118 °C | Vinegar, sharply sour, stinging the nose. No layer behind it. |
| 2,5-Dimethylpyrazine | 123-32-0 | 155 °C | Roasted, nutty, with a dry earthy note. This is the smell of something that has met fire and contains protein. |
| 2-Furfurylthiol | 98-02-2 | 155 °C | Roasted coffee in its purest form. At high concentration it becomes the smell of burnt rubber. |
| Butyric acid | 107-92-6 | 164 °C | Rancid butter, cheese, divisive. At very low concentration it gives a pleasant sense of richness — dose decides everything. |
| Dimethyl trisulfide | 3658-80-8 | 170 °C | Rotten onion, overcooked cabbage, with a metallic note. Very strong at extremely low concentration. |
| 2-Acetyl-1-pyrroline | 85213-22-5 | 181 °C | Freshly cooked sticky rice, pandan leaf, popcorn. A single molecule behind a whole region of food memory. |
| Furaneol | 3658-77-3 | 188 °C | Caramelised sugar, ripe strawberry, caramel. So sweet it can almost be read as a taste. |
| Dipropyl disulfide | 629-19-6 | 194 °C | Heat-treated onion, sweet and fatty. Without the pungency of raw onion. |
| Maltol | 118-71-8 | 200 °C | Burnt sugar, baked goods. |
| Naphthalene | 91-20-3 | 218 °C | Mothballs, asphalt, dry and dusty. Very particular and impossible to confuse. |
| trans-Anethole | 4180-23-8 | 234 °C | Star anise, round sweetness, slightly cool at the end. One of the few molecules almost nobody describes wrongly. |
| Lenthionine | 292-46-6 | 240 °C | Dried shiitake, rich, meaty, with deep umami. |
| 2,4,6-Trichloroanisole | 87-40-1 | 241 °C | Mould, damp rag, old paper. This is the smell of corked wine. |
| Indole | 120-72-9 | 253 °C | Overripe white flowers, faecal at high concentration. The most off-putting and also the most indispensable compound in the floral family. |
Two ways of ordering, two questions
Boiling point answers the question when do you smell this compound. It is the axis this site uses by default, because it maps directly onto what happens on a smelling strip.
Chemical family answers the question how does this compound behave: stable or fragile, soft or sharp, and how you recognise it on an analysis. Trade literature usually presents compound tables along this axis.
Neither axis is more correct than the other. Knowing both means you can read both kinds of document. Read about the boiling-point axis