20 compounds of this family in the library, boiling between 78 and 314 °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. Right of it are compounds heavier than the essential-oil range — they remain after the main axis has run out.
Structure
At least one hydroxyl group attached to the carbon skeleton. That group is polar and can form hydrogen bonds with neighbouring molecules.
Behaviour on a smelling strip
Hydrogen bonds hold them back, so they boil much higher than hydrocarbons of the same size. Limonene and linalool both have ten carbons; linalool boils twenty-two degrees higher just because of one hydroxyl group.
Compounds in this family
Ordered by rising boiling point — which is also the order in which you smell them.
| Compound | CAS | Boiling point | Description |
|---|---|---|---|
| Ethanol | 64-17-5 | 78 °C | Sharp, clean, cold, flat. No layer behind it. |
| cis-3-Hexenol | 928-96-1 | 156 °C | Freshly cut grass, harshly green, cold and wet. The molecule of plant injury. |
| 1-Octen-3-ol | 3391-86-4 | 175 °C | Freshly snapped mushroom, damp, slightly metallic. The human nose picks it up at extremely low concentration, so it is both a smell and an alarm bell. |
| 3-Octanol | 589-98-0 | 175 °C | Mushroom, earth, slightly fatty. Softer than 1-octen-3-ol and less fishy. |
| Linalool | 78-70-6 | 198 °C | Floral, slightly sweet, flat and almost without edges. On its own it is rather faint; its job is to be the ground the other components stand on. |
| 2-Methylisoborneol | 2371-42-8 | 207 °C | Damp earth, mould, dark cellar. Together with geosmin it builds the smell of first rain. |
| Terpinen-4-ol | 562-74-3 | 209 °C | Earthy, slightly medicinal, dry. Not pleasant on its own, but without it lavender loses its footing. |
| Menthol | 89-78-1 | 212 °C | Peppermint, icy in the nasal cavity. It does not lower the temperature; it only convinces the body that the temperature has dropped. |
| Borneol | 507-70-0 | 213 °C | Camphor but softer, with a damp-wood note. It is the gentle version of camphor. |
| α-Terpineol | 98-55-5 | 219 °C | Lilac, slightly soapy, soft. One of the molecules that act as connectors and are seldom noticed. |
| 2-Phenylethanol | 60-12-8 | 219 °C | Rose, honey, with a slight note of bread. Soft and round, with no edge at all. |
| Citronellol | 106-22-9 | 225 °C | Rose, soft, less harsh than geraniol. The same direction of smell, spoken more quietly. |
| Geraniol | 106-24-1 | 230 °C | Rose, sweet, slightly waxy. More lasting than citral and carries further on the skin. |
| Geosmin | 16423-19-1 | 270 °C | First rain, earth after rain, beetroot. The human nose detects it at a few parts per trillion — one of the lowest thresholds ever measured in humans. |
| Cedrol | 77-53-2 | 273 °C | Sweet, dry cedarwood with a slight camphor note. Richer than cedrene and far more lasting. |
| Nerolidol | 7212-44-4 | 276 °C | Floral wood, with a note of fresh bark and a hint of apple. A bridge between the floral and the woody-resinous families. |
| Patchoulol | 5986-55-0 | 287 °C | Earth, damp wood, deep sweetness. This is the compound that defines the smell of patchouli. |
| Guaiol | 489-86-1 | 288 °C | Damp wood, slightly rosy, with an earthy note. Softer than patchoulol and less sweet. |
| α-Santalol | 115-71-9 | 301 °C | Cream, milk, soft wood. Sweet without sugar, warm without heat. |
| α-Bisabolol | 515-69-5 | 314 °C | Faintly floral, softly sweet, with almost no edge. Very discreet for its weight. |
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