What Is 1,3,5-Undecatriene?
1,3,5-Undecatriene is an aroma chemical introduced to the perfumery palette in 1973 after researchers isolated its distinctive structure while exploring green note molecules. The material is produced through a controlled synthetic process that typically starts with readily available petrochemical feedstocks, followed by selective catalytic reactions that build its trio of double bonds in the correct positions. Because the route is well established and uses common raw inputs it is considered a fully synthetic ingredient rather than a natural extract.
At room temperature the substance appears as a clear to slightly honey toned liquid with a viscosity similar to light cooking oil. It is stable enough to ship and store without special inert-gas packaging which keeps handling costs down. Perfumers value its strong impact so only tiny amounts are required in a formula. This potency, combined with the efficiency of its manufacture, places it in the lower-to-middle price bracket compared with more exotic specialty molecules.
The material is widely used across fine fragrance and functional products because of its versatility, diffusion and reliability under the heat and pH swings found in soaps, detergents and candles. Although not every composition calls for it, most large fragrance houses keep it in their standard library and junior perfumers are taught to explore it early in their training.
What Does 1,3,5-Undecatriene Smell Like?
This ingredient sits firmly in the green family of odorants. Off a blotter it opens with an assertive snap of cut grass and crushed green leaves then quickly reveals a resinous galbanum character that feels both natural and airy. Within seconds a crisp green pepper facet emerges adding a subtle bite that keeps the profile lively. The overall impression is fresh outdoorsy greenery with a damp sap nuance that prevents any harshness.
Perfumers classify notes by the point at which they appear during evaporation. Top notes are the first impressions, middle notes form the heart and base notes provide lasting depth. 1,3,5-Undecatriene behaves largely as a top-to-heart bridge: it bursts on contact like a classic top note yet maintains strength long enough to color the heart for several hours. Used in citrus accords it lifts the opening while in floral or woody themes it injects a realistic leafy aspect without lingering into the drydown.
Projection is bold even at trace levels so a formula can smell greener and brighter with as little as 0.05 percent. Longevity is impressive for a green material, holding clear definition on a blotter for more than two days before fading to a faint vegetal whisper. On skin it usually registers for three to four hours which is ample time for the remaining accord to take over.
How & Where To Use 1,3,5-Undecatriene
This is one of those materials that makes a perfumer smile. It pours easily, behaves well in blends and does not have the sulfurous off notes that sometimes plague green molecules.
Its main role is to inject an instant burst of natural leafy freshness. In a citrus top accord a drop sharpens bergamot or grapefruit so the opening feels like fruit just peeled. In florals such as rose, muguet or narcissus it recreates crushed stems giving life to petals that might otherwise smell flat. It is also a secret weapon in woody and incense bases where a tiny trace cuts through heaviness and keeps the whole composition breathing.
Perfumers pick it over classic galbanum resinoid when they want a cleaner less earthy profile or need better stability in soap or detergent bases. Compared with cis-3-Hexenol it lasts longer and adds a peppery nuance that reads more sophisticated. You reach for it when the brief calls for crisp modern greenness without the opacity of vintage green accords.
Applications are wide ranging. In fine fragrance you will seldom exceed 0.3 % of the concentrate because it dominates quickly. Functional products tolerate a bit more but most formulas still sit below 0.2 %. Overdosing can push the pepper facet into harsh territory and may clash with delicate musks. In candles it survives the heat nicely yet keep the total wax content under 0.05 % to avoid a raw vegetable note during burn.
At trace levels it feels like morning dew on leaves. Around 0.1 % the green pepper bite becomes obvious and above 0.3 % the material turns almost mentholic and can mask lighter florals. Always build up slowly and check on skin and blotter before locking the level.
Prep work is minimal. Make a 10 % dilution in ethanol or dipropylene glycol so you can dose by drop and smell safely. The neat liquid can oxidise over long exposure to air so keep the bottle tightly closed and use nitrogen flushing if you own the equipment, although this is optional for most studio labs.
Safety Information
Certain precautions and considerations need to be observed whenever working with 1,3,5-Undecatriene.
- Always dilute before evaluation: prepare a 10 % or weaker solution and smell on a blotter rather than directly from the bottle.
- Ventilation: work in a fume hood or a well ventilated room to avoid inhaling concentrated vapors.
- Personal protective equipment: wear nitrile gloves and safety glasses to keep liquid away from skin and eyes.
- Health considerations: some aroma chemicals can cause irritation or allergic reactions. Seek medical advice before using if pregnant or breastfeeding and avoid prolonged or high-level exposure.
Always consult the latest Material Safety Data Sheet supplied by your vendor and review it regularly since revisions occur. Follow IFRA guidelines for maximum concentration in finished products to ensure consumer safety.
Storage And Disposal
When kept in a tight sealed bottle at room temperature 1,3,5-Undecatriene keeps its punch for around two years before the first signs of fade show up. Many labs still use stock that is three years old with no trouble yet plan on a 24-month window for best quality.
Cool is better than warm. A fridge set between 4-8 °C slows oxidation and can stretch shelf life well past the two-year mark. If fridge space is limited a cupboard that stays under 20 °C and never sees direct sun is fine.
Use polycone caps on both neat material and dilutions. They grip the glass and form an airtight seal that a dropper cap cannot match. Dropper bottles invite slow leaks and let air creep in which dulls the green bite.
Try to work from small bottles and top them up so headspace stays minimal. Less air means fewer oxygen molecules stealing freshness.
Label every container with the name 1,3,5-Undecatriene, the date filled, the percent dilution if any and the main safety notes like “Flammable liquid, skin irritant.” Clear labels prevent mix-ups during busy compounding sessions.
For disposal never pour neat material down the drain. First check local regulations. Most areas allow small leftovers to be mixed with an absorbent like cat litter then sealed and placed in chemical waste bins. Larger volumes should go to a licensed hazardous waste handler. The molecule is slowly biodegradable in soil and water yet still counts as an aquatic toxin at high levels so controlled disposal is the safe path.
Summary
1,3,5-Undecatriene is a synthetic green note that smells like crushed leaves, fresh galbanum and a snap of green pepper. A drop lifts citrus, brightens florals and cuts through heavy woods making it one of the most versatile tools on a perfumer’s bench.
It is potent, stable in most bases and sits in the mid price range so even hobby creators can play with it. Just remember it dominates fast, can skew peppery if overdosed and needs a firm cap to stay fresh.
Used with a light hand it brings life to almost any accord and keeps the finished scent feeling modern, airy and fun.