Alpha-Humulene (CAS 6753-98-6) — Green Top Note Fragrance Ingredient

ByThe Good Scents

Alpha-Humulene

CAS 6753-98-6

Origin
Note
IFRA
Generally safe
Data as of: Mar 2026

What Is Alpha-Humulene?

Alpha-Humulene is a natural hydrocarbon found in hops, sage, and ginseng. It contributes to the earthy, woody aroma of these plants. This molecule matters because it adds depth to fragrances, creating a connection to nature and herbal traditions in perfumery.

Safety Profile

GENERALLY SAFE
Generally safeUse with awarenessProfessional use
✓ No significant safety concerns
⚠ Check for oxidation products in aged materials
CAS
6753-98-6
Formula
Mixture
MW
Variable
Odor Family
Layer 1 · Enthusiast

What Does Alpha-Humulene Smell Like?

Alpha-Humulene offers a dry, woody-green character with subtle herbal nuances reminiscent of crushed sage leaves or fresh hop cones. Its aroma evolves from an initial crisp greenness to a warm, peppery woodiness in the dry-down. The scent profile carries faint echoes of damp forest floors and aged cedar chests, making it invaluable for creating naturalistic forest accords.

Scent Profile

In Famous Fragrances

Fragrance associations may not reflect actual formulations.

Terre d'Hermès(Hermès, 2006)

Alpha-Humulene contributes to the flinty mineral character that underpins this modern woody-citrus, adding depth to its vetiver heart.

Santal 33(Le Labo, 2011)

Used sparingly to enhance the dry, papery quality of the sandalwood accord and bridge the gap between green and woody notes.

Layer 2

2D Molecular Structure

alpha-Humulene

SMILES: C\C1=C/CC(C)(C)\C=C\C\C(C)=C\CC1

Chemistry, Properties & Perfumer Guide

The Chemistry

Alpha-Humulene is a sesquiterpene with a distinctive 11-membered ring structure. Found as a major component in hops essential oil (Humulus lupulus), it’s typically isolated through fractional distillation of plant extracts. The molecule exhibits interesting stereochemistry with multiple chiral centers that influence its odor profile. Industrial production often involves extraction from hop byproducts of the brewing industry.

Physical & Chemical Properties

Boiling Point~250 °C (est.)
StatePale yellow viscous liquid

Perfumer Guide

Note Position
Middle
Volatility
Medium (2-4 hours)
Blending
Good
ApplicationTypical %RangeNotes
Fine Fragrance0.5-2%Up to 5%Woody-herbal modifier
Functional Fragrance0.1-0.5%Up to 1%Natural freshness booster

Classic Accords

+ Patchouli + Vetiver = Dark Earth + Coriander + Juniper = Gin Accord

Tip: Use to add dryness and diffusion to woody bases without sweetness.

Alternatives & Comparisons

1
Beta-Caryophyllene CAS 87-44-5

More peppery with less green character; better for spicy accords where warmth is desired.

Layer 3

Safety, Regulatory & Sustainability

⚠ Regulatory Disclaimer

General reference only. IFRA, REACH, EU Cosmetics Regulation standards update periodically. Consult current IFRA Standards Library before formulating. Not legal or regulatory advice.

IFRA Status

No IFRA restrictions apply to alpha-humulene.

RIFM Assessment

RIFM assessment confirms safe use at current industry levels.

Sustainability

Alpha-Humulene is typically sourced as a byproduct of hop processing for the brewing industry, making its production relatively sustainable. Synthetic routes exist but are less common due to the availability of natural sources. The molecule is biodegradable and presents minimal environmental concerns.

Explore Alpha-Humulene

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References

  1. Brennecke et al. (2018). Sesquiterpene constituents in hop oils. Flavour and Fragrance Journal. DOI:10.1002/ffj.3456

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

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Ingredient Data Sheet

CAS 6753-98-6

Physical Properties

Molecular Weight204.35 g/mol🔬 PubChem
LogP (Octanol-Water)4.5🔬 PubChem
Boiling Point99 °C🔬 EPA CompTox
log Kp (skin permeability)-0.752💻 Calculated
SMILESCC1=CCC(C=CCC(=CCC1)C)(C)C🔬 PubChem

Volatility & Performance

Fragrance NoteTop💻 Calculated

Odor & Flavor

Primary Descriptorsbalsamicearthywoody• leffingwell
Functional Groupsalkene💻 RDKit

Sensory Thresholds

Odor Detection Threshold0.186 ppm (n=4)📖 van Gemert
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: DTXSID30858793

Physical Properties

Molecular Weight 204.357 g/mol🔬 EPA CompTox
Density 0.829 g/cm^3📊 OPERA
Boiling Point 261.206 °C📊 OPERA
Melting Point -51.742 °C📊 OPERA
Flash Point 96.475 °C📊 OPERA
Refractive Index 1.46 Dimensionless📊 OPERA
Molar Volume 249.408 cm^3/mol📊 OPERA

Partition & Solubility

LogP (Octanol-Water) 5.93 Log10 unitless📊 OPERA
LogD (pH 5.5) 5.93 Log10 unitless📊 OPERA
LogD (pH 7.4) 5.93 Log10 unitless📊 OPERA
LogKoa (Octanol-Air) 6.91 Log10 unitless📊 OPERA
Water Solubility 0 mol/L📊 OPERA
Henry's Law Constant 0.034 atm-m3/mole🔬 EPA CTX

Transport Properties

Vapor Pressure 0.027 mmHg📊 OPERA
Viscosity 4.087 cP📊 OPERA
Surface Tension 25.374 dyn/cm📊 OPERA
Thermal Conductivity 118.885 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 0 count💻 Computed
Aromatic Rings 0 count💻 Computed
Molar Refractivity 68.27 cm^3/mol📊 OPERA
Polarizability 27.064 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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