Material guide: Iso E Super — the invisible wood that can carry a whole perfume

Search our database for iso e super and the entry that appears is named patchouli ethanone. It does not come from patchouli, which makes this another entry in the names-versus-things lesson: the database keeps a systematic-style common name, the market calls it by IFF's trade name Iso E Super, and the papers call it OTNE. Three names, one molecule.

What matters

• Iso E Super is a transparent woody-amber molecule: dry, soft, like skin scent turned up. Medium strength, 79 suppliers, 172 hours of longevity (measured neat — a rare non-ceiling reading).
• It is famous enough that one brand sold a long-running perfume made of little else than this molecule (Molecule 01, trade lore) — the signature case of one molecule carrying a whole perfume.
• High-volume molecules draw heavy scientific scrutiny: a 2024 RIFM chronic aquatic assessment recommends a PNEC, and another paper the same year generated new-approach-methodology data indicating the thyroid effects are secondary to liver effects. Both are worth reading as written.

The basics

CAS	54464-57-2
Formula	C₁₆H₂₆O
MW	234.38
Odor	woody, dry, ambergris, cedar, old wood, ketonic, phenolic
Odor type	woody
Strength	medium
Longevity	172 hours (measured neat at 100%, on a blotter)
Appearance	colorless to pale yellow clear liquid
Flash point	111.11 °C
Shelf life	24 months or longer (cool, dark, sealed)
Listings	GRAS, JECFA, IFRA

172 hours is not the 400-hour ceiling of the scale (the vanillin guide explained the ceiling), and like ethylene brassylate's 208 it reads as genuinely measured: persistent, but not monster-grade. 79 suppliers is a blunt market vote.

For why Iso E Super, patchouli ethanone and OTNE can point to one material, see Why fragrance-material names so often mislead.

One molecule carrying a whole perfume

In perfumery lore, Iso E Super is shorthand for the big-dose skeleton: quiet on its own, never harsh even piled high, so it often gets laid down as the floor of an entire perfume. The extreme case is the brand that sold a perfume made of little else than this molecule (Molecule 01) into a long-running product — so the lore goes. To our noses, diluted it is a quiet, dry wood that comes and goes near the skin; people often describe it as "I can't smell it, but without it something's wrong." That flickering comes partly from olfactory fatigue and partly from individual differences; our practice is to re-smell several times during evaluation and resist quick verdicts.

It plays the same role as the two other quiet giants in this series:

Material	Suppliers	Longevity
Iso E Super	79	172 hours (neat)
Ambroxan	61	> 400 hours (at 10% dilution)
Ethylene brassylate	52	208 hours

All three are base materials that underwhelm on a blotter and collapse a formula when removed, and all three are commonly used in large doses.

A closely watched molecule: two 2024 checkups

Fragrance molecules produced at scale enter the routine inspection lists of environmental science and toxicology, and this one is no exception. We picked two 2024 papers to read as written. First, RIFM's chronic aquatic assessment in Environmental Toxicology and Chemistry:

OTNE is a high-production volume fragrance material used in various down-the-drain consumer products. ⋯ The 5th percentile hazardous concentration (HC5) derived from the cumulative probability distribution of the chronic toxicity values for the 11 species was determined to be 0.0498 mg/L. A series of "leave-one-out" and "add-one-in" simulations indicated the SSD was stable and robust. ⋯ Nevertheless, to further ensure the protection of the environment, an application factor of 2 to the HC5, resulting in a PNEC of 0.0249 mg/L, is recommended.

The same year, a paper in Food and Chemical Toxicology tackled a toxicology question: animal studies had observed thyroid-related effects — what is the mechanism?

Effects were observed on the thyroid and thyroid hormones, suggesting hypothalamic-pituitary-thyroid axis perturbation. ⋯ We investigated the molecular initiating events ⋯ using new approach methodologies (NAMs) ⋯ in vitro receptor ligand-binding assays ⋯ These data indicate the observed thyroid effects are secondary to liver effects and the thyroid effects, therefore, should not be the basis for assessing potential OTNE-induced human health hazards.

Both papers in plain terms: because this molecule is used at scale, it gets examined diligently and often. The aquatic assessment produced a recommended concentration with a safety factor built in, and on the thyroid question, data generated via new-approach methodologies (cell and receptor assays in place of additional animal experiments) indicate it sits downstream of liver effects. The hedges — "suggesting," "recommended," "should not be the basis" — stay as the authors wrote them; whether later research revises these conclusions is science working as usual.

When you smell it

• To our noses, a 10% dilution on a blotter opens as almost "clean air plus a hint of pencil shavings," and the woody-amber outline only sharpens after half an hour. Evaluate at 10% or below, and bring patience.
• It is more present on skin than on paper; this molecule gets along well with body heat. We tried it side by side with ambroxan on one strip: Iso E Super is drier and more transparent, with a notch less of the ambergris sweetness.
• Finding it "almost odorless" neat is normal. Judge it inside a formula.

Regulatory

Listed in GRAS, JECFA, and IFRA. These listings do not provide use limits. For skin-bound formulas check current IFRA Standards and the supplier's specification; the two papers above are the scientific basis of risk assessment, not formula limits — practical limits come from the current regulatory documents.

Buying notes

1. It is among the most versatile of the floor materials: cheap, stable, hard to ruin even in large doses. A good first choice for practicing woody bases.
2. Make a 10% dilution for evaluation; in real formulas it is often one of the largest single ingredients, so plan the overall structure before weighing.
3. For the full quiet-giants trilogy, buy a bottle each of this, ambroxan and ethylene brassylate and smell them side by side.

→ Iso E Super in the database: full physical data, supplier list, suggested pairings. → Ambroxan | Ethylene brassylate | Search by scent: try "woody dry ambergris" to find its neighbors.

References

A. Lapczynski, S. E. Belanger, K. Connors & J. Bozich, A Chronic Aquatic Hazard Assessment for the Perfume Raw Material Octahydro-tetramethyl-naphthalenyl-ethanone, Environmental Toxicology and Chemistry, 43(6), 1378–1389 (2024). PMID 38661477

E. Hulzebos, T. Stedeford, P. Sterchele & G. S. Ladics, Determination of OTNE-induced thyroid effects within an adverse outcome pathway (AOP) network, Food and Chemical Toxicology, 190, 114784 (2024). PMID 38834167