11 compounds of this family in the library, boiling between 162 and 285 °C. How the family spreads along the axis says something about its shared behaviour.
Structure
A carbonyl group at the end of the chain, with a hydrogen atom. This is the oxidation state between an alcohol and an acid.
Behaviour on a smelling strip
Sharp and strong. Many aldehydes have very low detection thresholds, so their effect is far greater than their percentage.
Compounds in this family
Ordered by rising boiling point — which is also the order in which you smell them.
| Compound | CAS | Boiling point | Description |
|---|---|---|---|
| Furfural | 98-01-1 | 162 °C | Almond, burnt bread, with a slight wood note. Dry sweetness. |
| 5-Methylfurfural | 620-02-0 | 187 °C | Caramel, roasted almond, with a slight spice note. Lightly burnt sweetness. |
| Citronellal | 106-23-0 | 207 °C | Green, slightly metallic, almost soapy. On its own it builds most of the smell of kaffir lime leaf. |
| Decanal | 112-31-2 | 208 °C | Orange peel, slightly fatty, waxy. The strange fatty note in Vietnamese coriander is this compound. |
| Neral | 106-26-3 | 227 °C | A softer lemon than geranial. |
| Citral | 5392-40-5 | 229 °C | Sharp lemon with body, slightly harsh. This is the lemon smell the food industry uses, not the smell of real lemon peel. |
| Geranial | 141-27-5 | 229 °C | Sharp lemon, edged, slightly metallic. This is the part that gives citral the harshness many people find a little coarse when smelled strongly. |
| Perillaldehyde | 2111-75-3 | 237 °C | Perilla, warm green, with a faint cinnamon note. Very distinctive and very hard to borrow from any other source. |
| Dodecanal | 112-54-9 | 238 °C | Fatty, waxy, slightly soapy. Heavier than decanal and less fresh. |
| Cinnamaldehyde | 104-55-2 | 248 °C | Cinnamon bark, hot sweetness, almost a taste. A single molecule responsible for the whole cinnamon tree in everyone’s memory. |
| Vanillin | 121-33-5 | 285 °C | Vanilla, warm sweetness, with a creamy note and a touch of wood. |
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