2,6,6-Trimethylcyclohex-2-ene-1,4-dione (CAS 1125-21-9) — Woody Base Note Fragrance Ingredient

ByThe Good Scents
Woody · Balsamic

2,6,6-Trimethylcyclohex-2-ene-1,4-dione

CAS 1125-21-9

Origin
synthetic
Note
Base
IFRA
Generally safe
Data as of: Apr 2026

What Is 2,6,6-Trimethylcyclohex-2-ene-1,4-dione?

2,6,6-Trimethylcyclohex-2-ene-1,4-dione is a synthetic fragrance ingredient used to add woody, earthy notes to perfumes. It is commonly found in masculine fragrances and colognes. This compound is valued for its ability to enhance longevity and add depth to fragrance compositions, making it a staple in modern perfumery.

Safety Profile

GENERALLY SAFE
Generally safeUse with awarenessProfessional use
✓ Safe in regulated products
⚠ Use with awareness in high concentrations
CAS
1125-21-9
Formula
Mixture
MW
Variable
Odor Family
Woody · Balsamic
Layer 1 · Enthusiast

What Does 2,6,6-Trimethylcyclohex-2-ene-1,4-dione Smell Like?

This ingredient offers a complex woody-earthy character with subtle smoky undertones. It evolves from a sharp, slightly green top note to a warm, resinous heart, finally settling into a dry, leathery base. Its behavior in dry-down is reminiscent of aged oak barrels, adding sophistication to fragrance profiles.

Scent Profile

In Famous Fragrances

Fragrance associations may not reflect actual formulations.

Sauvage(Dior, 2015)

Used to enhance the woody-ambery accord, providing a modern twist to the classic fougère structure.

Bleu de Chanel(Chanel, 2010)

Adds depth and longevity to the woody base, complementing the citrus and incense notes.

Layer 2

2D Molecular Structure

2,6,6-Trimethyl-2-cyclohexene-1,4-dione

SMILES: CC1=CC(=O)CC(C)(C)C1=O

Chemistry, Properties & Perfumer Guide

The Chemistry

2,6,6-Trimethylcyclohex-2-ene-1,4-dione is a cyclic diketone with a molecular formula of C9H12O2. It is synthesized through oxidation of trimethylcyclohexene derivatives. The compound’s rigid structure contributes to its stability and slow evaporation rate, making it ideal for base notes in perfumery.

Physical & Chemical Properties

Boiling PointN/A
DensityN/A

Perfumer Guide

Note Position
Base
Volatility
Low (hours)
Blending
Good
ApplicationTypical %RangeNotes
Fine Fragrance1-5%Up to 10%Adds woody depth

Classic Accords

Tip: Use in small amounts to avoid overpowering the composition.

Alternatives & Comparisons

1
Iso E Super CAS 54464-57-2

Offers similar woody notes but with a smoother, more diffusive character.

Layer 3

Safety, Regulatory & Sustainability

⚠ Regulatory Disclaimer

General reference only. Consult current IFRA Standards Library before formulating.

IFRA Status

No IFRA restrictions currently apply.

RIFM Assessment

RIFM assessment pending.

Sustainability

Synthesized from petrochemical precursors, this ingredient is produced in controlled industrial settings. Efforts are ongoing to develop more sustainable synthesis routes.

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References

  1. PubChem. 2,6,6-Trimethylcyclohex-2-ene-1,4-dione. PubChem

Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.

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Ingredient Data Sheet

CAS 1125-21-9

Physical Properties

Molecular Weight152.19 g/mol🔬 PubChem
LogP (Octanol-Water)1🔬 PubChem
Boiling Point92 °C🔬 EPA CompTox
Vapor Pressure0.0672 mmHg @ 25°C📊 OPERA
Involatility Index0.0059💻 Calculated
log Kp (skin permeability)-2.918💻 Calculated
SMILESCC1=CC(=O)CC(C1=O)(C)C🔬 PubChem

Volatility & Performance

Fragrance NoteTop💻 Calculated
Volatility ClassVery slow💻 Calculated
Persistence Score1.5 / 5💻 Calculated

Odor & Flavor

Primary Descriptorshayhoneyteatobacco• leffingwell
Functional Groupsketonealkene💻 RDKit

Sensory Thresholds

Odor Detection Threshold0.7608 ppm (n=6)📖 van Gemert

Regulatory Status

IOFI ClassificationNature Identical📖 Fenaroli
Data Sources & Attribution
Physical data: PubChem (NIH/NLM), U.S. EPA CompTox Dashboard, EPA OPERA models, RDKit. Odor & flavor: Arctander (Perfume & Flavor Chemicals), Fenaroli's Handbook of Flavor Ingredients, Leffingwell. Thresholds: van Gemert (Compilations of Odour Threshold Values). Regulatory: IFRA Standards 51st, FEMA GRAS. Trade names: Surburg (Common Fragrance & Flavor Materials). All data compiled and cross-referenced for perfumertools.com.

Physicochemical Properties

DTXSID: DTXSID9021685

Physical Properties

Molecular Weight 152.193 g/mol🔬 EPA CompTox
Density 1.03 g/cm^3🔬 EPA CTX
Boiling Point 220.7 °C🔬 EPA CTX
Melting Point 22.063 °C🔬 EPA CTX
Flash Point 89.925 °C📊 OPERA
Refractive Index 1.517 Dimensionless📊 OPERA
Molar Volume 140.917 cm^3/mol📊 OPERA

Partition & Solubility

LogP (Octanol-Water) 1.12 Log10 unitless🔬 EPA CTX
LogD (pH 5.5) 1.663 Log10 unitless📊 OPERA
LogD (pH 7.4) 1.662 Log10 unitless📊 OPERA
LogKoa (Octanol-Air) 5.07 Log10 unitless📊 OPERA
Water Solubility 0.132 mol/L🔬 EPA CTX
Henry's Law Constant 0 atm-m3/mole📊 OPERA

Transport Properties

Vapor Pressure 0.067 mmHg🔬 EPA CTX
Surface Tension 35.068 dyn/cm📊 OPERA

Molecular Descriptors

Topological Polar Surface Area 34.14 Ų💻 Computed
H-Bond Donors 0 count💻 Computed
H-Bond Acceptors 2 count💻 Computed
Rotatable Bonds 0 count💻 Computed
Aromatic Rings 0 count💻 Computed
Molar Refractivity 42.62 cm^3/mol📊 OPERA
Polarizability 16.896 Å^3📊 OPERA

Data Sources:

🔬 EPA Experimental data from U.S. EPA CompTox Chemicals Dashboard & CTX APIs. 📊 OPERA Predicted using EPA's OPERA QSAR models. 💻 Computed Calculated from SMILES using RDKit.

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