What Is 5-Methyl-2-Hepten-4-One?
5-Methyl-2-Hepten-4-One, sometimes referred to by flavor chemists as “filbertone,” is a small organic molecule first isolated from roasted hazelnuts in the mid-1980s. Today perfumers rely on an identical laboratory-made version because natural extraction from nuts is inefficient, season-dependent and yields only trace amounts. Commercial production usually starts with readily available aliphatic precursors that undergo a series of controlled oxidation and rearrangement steps, followed by careful distillation to reach a purity above 98 percent.
At room temperature the material is a clear, free-flowing liquid that ranges from colorless to a very pale straw yellow. It is lighter than water and shows a refractive index just under 1.45, which gives it a slight sparkling look when swirled in glass. With a flashpoint of 57 °C it sits in the safe handling zone for most fragrance operations yet still needs the usual precautions taken with any solvent-grade liquid.
The ingredient sees frequent use in fine fragrance as well as in functional products like shampoos, soaps and candles. Because synthesis is straightforward and uses economical starting materials it is generally viewed as an affordable workhorse rather than a luxury isolate, so creative teams can dose it generously without driving up formula cost.
What Does 5-Methyl-2-Hepten-4-One Smell Like?
This molecule is grouped in the gourmand family, the arena of edible, comforting notes. On a blotter it opens with an unmistakable roasted hazelnut facet that feels warm and slightly sweet, quickly joined by a fatty, almost buttery nuance that adds realism and mouth-watering depth. As the minutes pass a subtle toasted shell impression rises, giving the accord a lightly browned edge that keeps the sweetness from becoming cloying. Underneath, faint hints of cereal and soft brown sugar linger, rounding out the profile.
In the classical top-middle-base framework the material performs as a solid heart note. It appears a few minutes into the composition, bridges brightly volatile top accords like citrus or aldehydes, then supports darker base notes such as woods or musks. Projection is moderate; it radiates clearly for the first hour on a strip then settles close to the surface, still detectable for four to five hours before tapering away.
How & Where To Use 5-Methyl-2-Hepten-4-One
This is one of those materials that makes life in the lab a little easier. It pours cleanly, dilutes without fuss and brings instant personality to a blend so it tends to put perfumers in a good mood.
Its primary job is to supply a roasted hazelnut effect, so it shows up whenever a formula needs a nutty edible accent. In gourmand perfumes it partners beautifully with vanilla, praline bases and milky lactones, while in tobacco or coffee accords it deepens the roast and adds believable warmth. A small touch in woody ambers can suggest toasted oak or give a whiskey twist. It is rarely chosen for fresh citrus or marine compositions because the fatty nuance feels out of place there.
Typical levels in fine fragrance sit between 0.1 percent and 2 percent of the concentrate. Functional products that must fight through surfactants or wax can run higher, sometimes up to 5 percent, yet most of the time 0.5 percent is enough. At trace amounts it lends a soft nut skin halo, almost like the aroma that rises when you crack open a shell. Push it higher and the sweetness climbs, the buttery facet blooms and a slightly oily edge can creep in, which some creatives use on purpose for realism while others dial back with dry woods or musks.
Before weighing into a formula many perfumers make a 10 percent ethanol or DPG solution. This tames the flash of raw strength and lets them judge its behavior alongside other materials at comparable dilution. No special stabilizers or antioxidants are usually required, as the molecule is stable under normal fragrance conditions.
Safely Information
As with any aroma chemical a few simple precautions keep work both pleasant and safe.
- Always dilute before evaluation: prepare a low-percentage solution so you can smell nuances without overwhelming your nose
- Avoid direct sniffing from the bottle: headspace inside the vial can contain concentrated vapors that may irritate nasal passages
- Work in good ventilation: a fume hood or open area prevents build-up of airborne material during weighing or blending
- Wear gloves and safety glasses: the liquid can defat skin and temporary contact with eyes causes discomfort so basic PPE is recommended
- Health considerations: some individuals experience skin irritation or sensitization from aroma chemicals, seek medical advice before use if pregnant or breastfeeding and remember that prolonged exposure to high concentrations may be harmful even though brief low-level contact is generally considered safe
Consult the most recent MSDS from your supplier for detailed data, keep an eye on updates and respect any IFRA restrictions that apply to your specific end product category to ensure the material stays an asset rather than a hazard.
Storage And Disposal
When kept in ideal conditions 5-Methyl-2-Hepten-4-One remains in spec for roughly two to three years, sometimes longer if oxygen exposure is minimal. Refrigeration is not mandatory but a steady temperature around 5 °C can squeeze out extra months of freshness. Otherwise a shelf in a cool dry cupboard away from sunlight and hot pipes does the job.
Use bottles fitted with polycone caps for both neat material and working dilutions. The flexible inner liner forms a tight seal that stops slow evaporation and vapor leaks, something a glass dropper top cannot achieve. Top up containers whenever possible so the headspace stays small and less air means less oxidation.
Store the material in amber or aluminum bottles, wipe threads after pouring and log the opening date on the label. Clear identification prevents mix-ups: print the INCI or common name, batch number, flashpoint symbol and any personal protective gear required during handling.
Small laboratory volumes that are no longer needed can be mixed with an absorbent such as vermiculite then disposed of as hazardous organic waste according to local regulations. Do not pour into drains because the liquid is insoluble in water and can film on the surface. Industrial quantities should go to a licensed chemical incinerator capable of high temperature destruction. The molecule is not considered readily biodegradable so responsible disposal protects waterways as well as workplace safety.
Summary
5-Methyl-2-Hepten-4-One is a lab-made replica of the aroma that floats from freshly roasted hazelnuts. It smells nutty sweet and a little buttery which lets perfumers build mouth-watering praline, coffee or toasted wood accords with just a few drops.
The material is affordable, stable under normal conditions and blends effortlessly into both fine fragrance and functional bases. Its specificity means it shines when a formula calls for a clear edible nut accent yet may feel out of place in very fresh or aquatic styles.
In short it is a fun tool that slots into countless gourmand themes, deepens tobacco or whiskey ideas and brings comforting warmth to candles shampoo or soap without breaking the budget. Keep it cool, keep it capped and enjoy the creative wiggle room it offers.