17 compounds of this family in the library, boiling between 152 and 186 °C. How the family spreads along the axis says something about its shared behaviour.
Structure
Ten carbon atoms, no functional group. This is the bare skeleton of plant chemistry — two isoprene units joined together, nothing more.
Behaviour on a smelling strip
The lightest and fastest-evaporating of all the families. They occupy the front of the volatility band and vanish from a smelling strip within minutes. If a sample opens bright and sharp and then drops away quickly, most of that is this group’s work.
Compounds in this family
Ordered by rising boiling point — which is also the order in which you smell them.
| Compound | CAS | Boiling point | Description |
|---|---|---|---|
| α-Thujene | 2867-05-2 | 152 °C | Thin wood, slightly pungent, with a dry herbal note. Very light and gone almost instantly. |
| α-Pinene | 80-56-8 | 155 °C | Pine, dry, sharp. It evaporates so fast it has usually left before you can name it. |
| Camphene | 79-92-5 | 159 °C | Faint camphor, dry, slightly piney. It is the bridge between the pine group and the camphor group. |
| Sabinene | 3387-41-5 | 163 °C | Woody, slightly peppery, dry. A small presence, but it sharpens the edges of the whole mixture. |
| β-Pinene | 127-91-3 | 166 °C | Pine, but darker and less sweet than alpha-pinene. The two differ only in the position of one double bond, and the human nose can tell them apart. |
| Myrcene | 123-35-3 | 167 °C | Green, slightly resinous, with a faint earthy note. Rather coarse on its own, but it links the citrus part to the green part. |
| δ-3-Carene | 13466-78-9 | 170 °C | Pine, sweet, with a clear resinous note. This is the compound that gives turpentine oil its most characteristic part. |
| β-Phellandrene | 555-10-2 | 172 °C | Mint, slightly citrus, with a light wood note. Close to α-phellandrene but cleaner. |
| α-Terpinene | 99-86-5 | 175 °C | Faint lemon, thin wood, with a slight herbal note. Less sharp than limonene. |
| α-Phellandrene | 99-83-2 | 175 °C | Faint mint, wood, with a slight citrus note. Greener than limonene and less sweet. |
| Limonene | 138-86-3 | 176 °C | Citrus peel, bright, slightly bitter at the edges. This is the most common molecule in the whole fragrance trade, and also one everyone has smelled after it has gone off — the smell of old peel is oxidised limonene. It is not the terpene that spoils fastest; α-terpinene and α-phellandrene are quicker still. But because limonene is everywhere, its trace of decay is the one we know best. |
| cis-β-Ocimene | 3338-55-4 | 177 °C | Green, lightly sweet, with a grassy note. Thin and short-lived — it is the coat of paint, not the frame. |
| p-Cymene | 99-87-6 | 177 °C | Dry, light wood, with a slight solvent note. Fainter than most other monoterpenes and without any freshness. |
| (E)-β-Ocimene | 3779-61-1 | 177 °C | Sweet, floral, slightly herbal. Light and much faster to evaporate than the ring terpenes. |
| p-Menth-1-ene | 1461-27-4 | 177 °C | Faint wood, slightly citrus, with almost no edge. Rarely the main compound anywhere, but worth knowing because it is the simplest form of the skeleton many familiar components share. |
| γ-Terpinene | 99-85-4 | 183 °C | Dry citrus, slightly woody, not very sweet. It is the backbone of the smell of fruit peel. |
| Terpinolene | 586-62-9 | 186 °C | Lightly sweet, piney, with a slight floral note. Softer than the other monoterpenes. |
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