1,3-Undecadien-5-yne (CAS 166432-52-6) — Green Top to middle Note Fragrance Ingredient

ByThe Good Scents
Green · Woody

1,3-Undecadien-5-yne

CAS 166432-52-6

Origin
synthetic
Note
Top to middle
IFRA
Use with awareness
Data as of: Apr 2026

What Is 1,3-Undecadien-5-yne?

1,3-Undecadien-5-yne is a synthetic fragrance ingredient used in niche perfumery. It’s a rare alkyne-diene compound that contributes unique green-metallic nuances. This molecule is typically found in avant-garde fragrances pushing olfactory boundaries.

Safety Profile

USE WITH AWARENESS
Generally safeUse with awarenessProfessional use
⚠ Limited safety data available
⚠ Handle with proper ventilation
CAS
166432-52-6
Formula
Mixture
MW
Variable
Odor Family
Green · Woody
Layer 1 · Enthusiast

What Does 1,3-Undecadien-5-yne Smell Like?

A razor-sharp green character with metallic undertones, reminiscent of freshly cut stems and crushed galbanum. The alkyne group contributes a piercing, almost electric quality that evolves into a cleaner, more diffusive green note during dry-down. Imagine the scent of green bell peppers sliced with a stainless steel knife, transitioning to the vegetal freshness of snap peas.

Scent Profile
Layer 2

2D Molecular Structure

(3E)-Undeca-1,3-dien-5-yne

SMILES: CCCCCC#C\C=C\C=C

Chemistry, Properties & Perfumer Guide

The Chemistry

1,3-Undecadien-5-yne belongs to the rare class of conjugated enyne compounds, featuring both a diene and alkyne functional group. The linear C11 structure with alternating double and triple bonds creates unique electron delocalization. Synthesized through controlled alkyne coupling reactions, this molecule’s reactivity requires careful handling. The conjugated system is responsible for its intense green character and unusual stability among unsaturated hydrocarbons.

Physical & Chemical Properties

Perfumer Guide

Note Position
Top to middle
Volatility
Medium (2-4 hours)
Blending
Challenging
ApplicationTypical %RangeNotes
Fine Fragrance0.01-0.1%Up to 0.3%For radical green effects
Functional FragranceNot usedN/AToo unconventional

Classic Accords

Tip: Stabilize with antioxidants to prevent polymerization during storage.

Alternatives & Comparisons

1
1-Undecen-3-yne CAS 1000273-93-8

Simpler structure with similar green-metallic profile but less tenacity.

Layer 3

Safety, Regulatory & Sustainability

⚠ Regulatory Disclaimer

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

IFRA Status

Not currently restricted by IFRA due to extremely limited usage.

RIFM Assessment

No RIFM assessment available for this rare material.

Sustainability

As a synthetic material produced in small quantities, environmental impact is minimal but energy-intensive synthesis should be considered. No natural sources exist for this compound, making it dependent on petrochemical feedstocks.

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References

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

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    Ingredient Data Sheet

    CAS 166432-52-6

    Physical Properties

    Molecular Weight148.24 g/mol🔬 PubChem
    LogP (Octanol-Water)4.5🔬 PubChem
    Boiling Point189 °C🔬 EPA CompTox
    Vapor Pressure0.7079 mmHg @ 25°C📊 OPERA
    Flash Point75.5 °C🔬 EPA CompTox
    Involatility Index0.0627💻 Calculated
    log Kp (skin permeability)-0.409💻 Calculated
    SMILESCCCCCC#CC=CC=C🔬 PubChem

    Volatility & Performance

    Fragrance NoteTop💻 Calculated
    Volatility ClassSlow💻 Calculated
    Persistence Score0.5 / 5💻 Calculated

    Odor & Flavor

    Functional Groupsalkene💻 RDKit
    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: DTXSID6051776

    Physical Properties

    Molecular Weight 148.249 g/mol🔬 EPA CompTox
    Density 0.802 g/cm^3📊 OPERA
    Boiling Point 200.128 °C📊 OPERA
    Melting Point -48.352 °C📊 OPERA
    Flash Point 68.734 °C📊 OPERA
    Refractive Index 1.47 Dimensionless📊 OPERA
    Molar Volume 182.123 cm^3/mol📊 OPERA

    Partition & Solubility

    LogP (Octanol-Water) 4.351 Log10 unitless📊 OPERA
    LogD (pH 5.5) 4.351 Log10 unitless📊 OPERA
    LogD (pH 7.4) 4.351 Log10 unitless📊 OPERA
    LogKoa (Octanol-Air) 4.53 Log10 unitless📊 OPERA
    Water Solubility 0.001 mol/L📊 OPERA
    Henry's Law Constant 0.017 atm-m3/mole📊 OPERA

    Transport Properties

    Vapor Pressure 0.943 mmHg📊 OPERA
    Viscosity 0.831 cP📊 OPERA
    Surface Tension 25.945 dyn/cm📊 OPERA
    Thermal Conductivity 135.708 mW/(m*K)📊 OPERA

    Molecular Descriptors

    Topological Polar Surface Area 0 Ų💻 Computed
    H-Bond Donors 0 count💻 Computed
    H-Bond Acceptors 0 count💻 Computed
    Rotatable Bonds 4 count💻 Computed
    Aromatic Rings 0 count💻 Computed
    Molar Refractivity 50.799 cm^3/mol📊 OPERA
    Polarizability 20.138 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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