3-Hexenyl 2-oxopropionate (CAS 68133-76-6) — Green Top to middle Note Fragrance Ingredient

ByThe Good Scents
Green · Sweet

3-Hexenyl 2-oxopropionate

CAS 68133-76-6

Origin
synthetic
Note
Top to middle
IFRA
Generally safe
Data as of: Apr 2026

What Is 3-Hexenyl 2-oxopropionate?

3-Hexenyl 2-oxopropionate is a synthetic fragrance ingredient used to add fresh, green, and fruity nuances to perfumes and scented products. You might encounter it in air fresheners, body care products, or fine fragrances where a crisp, natural green character is desired. This molecule matters because it helps recreate the vibrant, just-crushed-leaf aroma of nature without relying on volatile plant extracts that can fade quickly.

Safety Profile

GENERALLY SAFE
Generally safeUse with awarenessProfessional use
✓ No major restrictions in current IFRA guidelines
✓ Not classified as an EU allergen
CAS
68133-76-6
Formula
Mixture
MW
Variable
Odor Family
Green · Sweet
Layer 1 · Enthusiast

What Does 3-Hexenyl 2-oxopropionate Smell Like?

3-Hexenyl 2-oxopropionate delivers an intensely green, slightly waxy opening reminiscent of freshly torn ivy leaves or unripe bananas. The initial burst evolves into a cleaner, more transparent heart with subtle pear-like fruitiness and a faintly herbal undertone. As it dries down, it leaves a delicate green tea impression with whisper-thin woody facets. The overall effect is like walking through a greenhouse just after watering – that perfect balance of chlorophyll-rich vegetation and damp earthiness.

Scent Profile
Layer 2

2D Molecular Structure

Propanoic acid, 2-oxo-, (3Z)-3-hexen-1-yl ester

SMILES: CC\C=C/CCOC(=O)C(C)=O

Chemistry, Properties & Perfumer Guide

The Chemistry

3-Hexenyl 2-oxopropionate is a synthetic ester formed by the condensation of 3-hexen-1-ol with pyruvic acid. As an unsaturated ester, it belongs to the class of green leaf volatiles (GLVs) that plants naturally produce when tissues are damaged. Industrially, it’s typically synthesized through acid-catalyzed esterification under controlled conditions to preserve the delicate cis-3-hexenyl moiety. The molecular structure features both ester and ketone functional groups, which contribute to its complex odor profile and moderate stability in formulations.

Physical & Chemical Properties

AppearanceColorless to pale yellow liquid
Odor Threshold~0.5 ppb in air

Perfumer Guide

Note Position
Top to middle
Volatility
Moderate (2-4 hours)
Blending
Good
ApplicationTypical %RangeNotes
Fine Fragrance0.5-2%Up to 5%Green modifier for floral and citrus compositions
Functional Fragrances0.1-0.5%Up to 1%Fresh top note in detergents and cleaners
Personal Care0.2-1%Up to 3%Natural green accent in shower gels and shampoos

Classic Accords

Tip: Stabilize in ethanol-heavy bases to prevent ester hydrolysis over time.

Alternatives & Comparisons

1
Cis-3-Hexenyl Acetate CAS 3681-71-8

More intense green character with shorter duration, ideal when a sharper top note is needed.

2
Hexyl 2-Oxopropionate CAS 142-92-7

Less green but more fruity, useful when a softer, apple-like nuance is preferred.

Layer 3

Safety, Regulatory & Sustainability

⚠ Regulatory Disclaimer

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

IFRA Status

No current IFRA restrictions. Not listed in any IFRA amendment as of 2023.

RIFM Assessment

RIFM safety assessment pending. Preliminary data suggests low sensitization potential.

Sustainability

As a fully synthetic material, 3-Hexenyl 2-oxopropionate avoids agricultural land use and seasonal variability associated with natural green notes. Production typically uses petrochemical feedstocks, though some manufacturers are exploring bio-based routes using fermented hexenol precursors. The ester’s potency means very small quantities are needed in formulations, reducing overall environmental load compared to less powerful green alternatives.

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References

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

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    Ingredient Data Sheet

    CAS 68133-76-6

    Physical Properties

    Molecular Weight170.21 g/mol🔬 PubChem
    LogP (Octanol-Water)1.8🔬 PubChem
    Boiling Point75 °C🔬 EPA CompTox
    log Kp (skin permeability)-2.46💻 Calculated
    SMILESCCC=CCCOC(=O)C(=O)C🔬 PubChem

    Volatility & Performance

    Fragrance NoteTop💻 Calculated

    Odor & Flavor

    Primary Descriptorscaramelgreenspicy• leffingwell
    Functional Groupsketoneesteretheralkene💻 RDKit
    (Z)-3-Hexenyl pyruvate has a green, spicy, caramellic odor.📖 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: DTXSID20887178

    Physical Properties

    Molecular Weight 170.208 g/mol🔬 EPA CompTox
    Density 0.992 g/cm^3📊 OPERA
    Boiling Point 225.274 °C📊 OPERA
    Melting Point -23.571 °C📊 OPERA
    Flash Point 88.359 °C📊 OPERA
    Refractive Index 1.445 Dimensionless📊 OPERA
    Molar Volume 171.313 cm^3/mol📊 OPERA

    Partition & Solubility

    LogP (Octanol-Water) 2.032 Log10 unitless📊 OPERA
    LogD (pH 5.5) 2.032 Log10 unitless📊 OPERA
    LogD (pH 7.4) 2.032 Log10 unitless📊 OPERA
    LogKoa (Octanol-Air) 5.08 Log10 unitless📊 OPERA
    Water Solubility 0.055 mol/L📊 OPERA
    Henry's Law Constant 0 atm-m3/mole📊 OPERA

    Transport Properties

    Vapor Pressure 0.115 mmHg📊 OPERA
    Viscosity 1.45 cP📊 OPERA
    Surface Tension 31.02 dyn/cm📊 OPERA
    Thermal Conductivity 145.119 mW/(m*K)📊 OPERA

    Molecular Descriptors

    Topological Polar Surface Area 43.37 Ų💻 Computed
    H-Bond Donors 0 count💻 Computed
    H-Bond Acceptors 3 count💻 Computed
    Rotatable Bonds 5 count💻 Computed
    Aromatic Rings 0 count💻 Computed
    Molar Refractivity 45.607 cm^3/mol📊 OPERA
    Polarizability 18.08 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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