2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl- (CAS 21835-00-7) — Woody Middle Note Fragrance Ingredient

Woody · Spicy

2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl-

CAS 21835-00-7

Origin
synthetic
Note
Middle
IFRA
Use with awareness
Data as of: Apr 2026

What Is 2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl-?

2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl- is a synthetic aroma chemical used in fragrances to create unique, complex notes. It is found in niche perfumery and specialty formulations. This ingredient matters because it adds depth and character to fragrances, often contributing to woody or spicy accords where traditional materials fall short.

Safety Profile

USE WITH AWARENESS
Generally safeUse with awarenessProfessional use
Safe in regulated products
Potential sensitizer – use caution
CAS
21835-00-7
Formula
Mixture
MW
Variable
Odor Family
Woody · Spicy
Layer 1 · Enthusiast

What Does 2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl- Smell Like?

This molecule offers a intriguing olfactory profile, starting with a sharp, slightly medicinal top note that quickly evolves into a warm, woody-spicy heart. The dry-down reveals a subtle sweetness, reminiscent of aged leather or tobacco. Its complexity makes it a valuable tool for perfumers seeking to create unconventional, modern accords.

Scent Profile
Layer 2

2D Molecular Structure

2-Hydroxy-3,4-dimethylcyclopent-2-en-1-one

SMILES: CC1CC(=O)C(O)=C1C

Chemistry, Properties & Perfumer Guide

The Chemistry

2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl- belongs to the cyclopentenone class of compounds. These molecules are characterized by a five-membered ring containing a ketone group. The hydroxyl and methyl substitutions influence both the physical properties and olfactory characteristics. Synthesis typically involves condensation reactions followed by selective oxidation and methylation steps.

Physical & Chemical Properties

Boiling PointN/A
DensityN/A

Perfumer Guide

Note Position
Middle
Volatility
Medium (2-4 hours)
Blending
Good
ApplicationTypical %RangeNotes
Fine Fragrance0.5-2%Up to 5%Adds complexity to woody bases
Functional Fragrance0.1-1%Up to 3%Used in masculine accords

Classic Accords

Tip: Use sparingly to avoid overpowering other notes.

Alternatives & Comparisons

1
2,3-Dimethyl-2-cyclopenten-1-one CAS 1121-05-7

Similar woody character but less sweet. Use when a drier effect is desired.

Layer 3

Safety, Regulatory & Sustainability

⚠ Regulatory Disclaimer

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

IFRA Status

No specific IFRA restrictions identified.

RIFM Assessment

No RIFM safety assessment currently available.

Sustainability

As a synthetic material, this compound’s environmental impact depends on manufacturing processes. Being produced in controlled laboratory settings typically results in lower ecological impact than some natural alternatives.

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References

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

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    Physicochemical Properties

    DTXSID: DTXSID5051864

    Physical Properties

    Molecular Weight 126.155 g/mol🔬 EPA CompTox
    Density 1.071 g/cm^3📊 OPERA
    Boiling Point 193.941 °C📊 OPERA
    Melting Point 44.966 °C📊 OPERA
    Flash Point 77.746 °C📊 OPERA
    Refractive Index 1.451 Dimensionless📊 OPERA
    Molar Volume 121.694 cm^3/mol📊 OPERA

    Partition & Solubility

    LogP (Octanol-Water) 0.581 Log10 unitless📊 OPERA
    LogD (pH 5.5) 0.581 Log10 unitless📊 OPERA
    LogD (pH 7.4) 0.581 Log10 unitless📊 OPERA
    LogKoa (Octanol-Air) 4.56 Log10 unitless📊 OPERA
    Water Solubility 0.268 mol/L📊 OPERA
    Henry's Law Constant 0 atm-m3/mole📊 OPERA

    Transport Properties

    Vapor Pressure 0.438 mmHg📊 OPERA
    Surface Tension 34.718 dyn/cm📊 OPERA

    Molecular Descriptors

    Topological Polar Surface Area 37.3 Ų💻 Computed
    H-Bond Donors 1 count💻 Computed
    H-Bond Acceptors 2 count💻 Computed
    Rotatable Bonds 0 count💻 Computed
    Aromatic Rings 0 count💻 Computed
    Molar Refractivity 32.736 cm^3/mol📊 OPERA
    Polarizability 12.977 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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