What Is 2-Undecenal?
2-Undecenal is an aroma chemical belonging to the family of aliphatic aldehydes. It was first reported by flavor chemists in the early 1960s when researchers were cataloging volatile compounds that occur naturally in plants and fruits. Although small amounts are found in nature, the material used in perfumery today is produced synthetically to guarantee purity and consistent quality.
Industrial production usually starts with an 11-carbon alcohol or olefin. Through controlled oxidation the alcohol is converted into an aldehyde, or through hydroformylation and subsequent processing the olefin is transformed into the same target molecule. These routes give a high-yield, high-purity product suitable for fragrance work.
At room temperature the finished material is a thin liquid that looks almost water-clear, sometimes picking up a faint straw tint after long storage. It pours easily and blends well with both oils and alcohol.
Perfumers reach for 2-Undecenal when they need a bright aldehydic accent that is less sharp than the classic soapy C-12 aldehydes. It finds steady use across fine fragrance, personal wash, household care and candle formulas, making it a familiar tool on the blending bench. Thanks to efficient manufacturing methods it is considered reasonably priced and is stocked by most fragrance houses.
What Does 2-Undecenal Smell Like?
Most professionals group 2-Undecenal within the citrus family because its first impression recalls the zest of a freshly peeled orange.
Off a blotter the material opens with a lively burst of sweet citrus layered with a gentle fruity tone that hints at tangerine or juicy mandarin. Almost at once an aldehydic sparkle appears, giving the scent a clean airy lift while a soft waxy facet keeps it from feeling acidic. As minutes pass the fruitiness mellows into a smoother peel nuance that remains pleasant rather than turning pithy or bitter.
In the classical top, middle and base structure 2-Undecenal behaves as an upper-mid note. It rises quickly to announce itself then lingers long enough to bridge into the heart of a composition, helping other notes feel brighter without vanishing too soon.
Projection is strong for the first hour because the molecule is highly diffusive, allowing small dosages to influence an entire accord. Despite its lively opening the chemical is surprisingly tenacious, with traces still detectable on a blotter after two days which is an advantage when formulating products that need lasting freshness.
How & Where To Use 2-Undecenal
Simply put 2-Undecenal is a pleasure to handle. It pours easily, folds into both oil and alcohol bases without fuss and its bright personality shows itself even in tiny amounts.
Perfumers treat it as an orange-zest spotlight that can freshen almost any top accord. In citrus colognes it lifts natural orange or mandarin without pushing the cost through the roof. In florals such as rose or lavender it adds a juicy sparkle that keeps the bouquet feeling dewy rather than dusty. Herbal themes like clary sage and resinous notes like opopanax also benefit from its clean aldehydic sheen which adds diffusion while trimming heaviness.
The material is powerful so most formulas keep it in the 0.05 % to 0.5 % range. The officially suggested ceiling is 1 % but very bold household cleaners may inch toward 2 %. Above that level the note starts to dominate, shifting from fruity zest to a sharper, waxier aldehyde that can feel soapy or even metallic. In trace amounts it merely brightens other ingredients giving the impression of fresh air around the composition.
Because it lasts over 48 hours on a blotter 2-Undecenal helps fix the citrus impression in products that normally lose freshness fast. That makes it handy in shampoos, shower gels, detergents, fabric softeners and candles where heat or water would otherwise strip lighter top notes.
There is very little prep work required. A quick shake before weighing ensures homogeneity because minor crystallisation can occur in a cold lab. If blending into an all-water base pre-solubilise it in a small amount of ethanol or dipropylene glycol to keep the mixture clear.
Safety Information
Like all fragrance raw materials 2-Undecenal should be treated with care to keep workspaces safe and formulas compliant.
- Always dilute before evaluation: make a quick solution in alcohol or dipropylene glycol before smelling to avoid overwhelming the nose
- Avoid sniffing from the bottle: headspace inside the vial can carry vapor strong enough to irritate mucous membranes
- Work in good ventilation: an extractor hood or open bench discourages buildup of airborne aldehyde fumes
- Wear gloves and goggles: the liquid can defat skin and aldehydes are notorious eye irritants so physical barriers are your first defense
- Health considerations: aldehydes may trigger skin irritation or sensitisation in susceptible individuals therefore limit direct contact seek medical advice if pregnant or breastfeeding and remember that chronic or high-level exposure poses greater risk than occasional low-level work
Before every project consult the latest MSDS issued by your supplier and revisit it whenever a new revision appears. Follow current IFRA guidelines for maximum usage in each product category to ensure your creations are both enjoyable and safe.
Storage And Disposal
When stored with care 2-Undecenal stays in good shape for roughly two years from the date the drum or bottle is opened. Many labs keep it usable even longer but a 24-month target is a safe rule of thumb.
A refrigerator is helpful yet not essential. Cool room temperature out of direct light works well as long as the space stays below about 20 °C. Heat, sunlight and frequent temperature swings speed up oxidation and should be avoided.
Choose bottles with tight polycone caps for both neat material and dilutions. Polycone inserts form a better seal than droppers so less air reaches the liquid. Droppers also drip after repeated use which wastes product and can gum up threads.
Keep containers as full as practical. A smaller headspace means less oxygen and less chance the citrus note will fade or turn waxy. If a large bottle is only half used decant the remainder into a smaller amber vial.
Label every container clearly with the name 2-Undecenal, the date it was opened, the strength of any dilution and standard hazard pictograms. Good labels save time and stop mix-ups later on.
For disposal follow local rules for organic solvents. Small lab quantities can often go into the flammable waste stream that is later incinerated. Do not pour strong solutions straight down the drain. Although aliphatic aldehydes do break down in the environment they can still harm aquatic life in concentrated form. Rinse empty bottles with a little alcohol, add the rinse to your waste can then recycle the clean glass if services allow.
Summary
2-Undecenal is a synthetically produced citrus aldehyde that smells like bright sweet orange peel with a light fruity twist. It acts as a lively upper-mid note that adds sheen and lift to citrus, floral, herbal and resin accords. Perfumers like it because a few drops make a blend sparkle and its power helps freshness last far beyond what natural zest can deliver.
The material is affordable, stable in most product bases and easy to mix so it shows up in fine fragrance, soaps, cleaners and candles. Keep in mind that a light hand is best and that oxygen will dull the scent over time. Store it cool, cap it tight and you will have a fun, reliable tool ready to brighten almost any formula.