2-Methyl-2-pentenal (CAS 623-36-9) — Green Top Note Fragrance Ingredient
2-Methyl-2-pentenal
CAS 623-36-9
What Is 2-Methyl-2-pentenal?
2-Methyl-2-pentenal is a synthetic fragrance ingredient used to add green, fruity, and slightly metallic nuances to perfumes. It’s often found in modern floral and fruity fragrances. This aldehyde contributes freshness and lift to top notes, making it valuable for creating vibrant, contemporary scents.
Safety Profile
GENERALLY SAFEWhat Does 2-Methyl-2-pentenal Smell Like?
2-Methyl-2-pentenal opens with a sharp, green burst reminiscent of freshly crushed leaves, evolving into a fruity character akin to underripe apples. The metallic edge adds modernity, while the dry-down reveals a subtle nuttiness. Its behavior is linear but impactful, serving as a crisp accent rather than a dominant player.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used to amplify the green galbanum note, creating a cutting-edge chlorophyll effect that defined mid-century freshness.
Provides a crisp green counterpoint to the citrus top notes, enhancing the fragrance’s modern masculinity.
2D Molecular Structure
SMILES: CCC=C(C)C=O
Chemistry, Properties & Perfumer Guide
The Chemistry
2-Methyl-2-pentenal is an α,β-unsaturated aldehyde with the formula C6H10O. It’s synthesized via aldol condensation of propionaldehyde. The double bond conjugation contributes to its reactivity and distinctive odor profile. This molecule exists as E/Z isomers, with the E-isomer being more stable and prevalent in fragrance applications.
Physical & Chemical Properties
| Boiling Point | 134-136 °C |
|---|---|
| Density | 0.846 g/cm³ |
| Refractive Index | 1.432 |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Green accent note |
| Functional Fragrance | 0.05-0.2% | Up to 0.5% | Freshness booster |
Classic Accords
Tip: Use sparingly to avoid overwhelming compositions with its metallic green character.
Alternatives & Comparisons
More intensely green, less fruity. Used when a stronger leaf alcohol character is desired.
Grassier and less metallic. Preferred for naturalistic green effects.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not currently restricted by IFRA. Monitor for sensitization potential at high concentrations.
EU Allergen Declaration
Not listed as an EU allergen.
GHS Classification
RIFM Assessment
RIFM has evaluated this material and found it safe at current usage levels.
Sustainability
Synthesized from petrochemical precursors. Production requires careful waste management due to aldehyde reactivity. No known natural sources, making synthetic production the only viable option for perfumery use.
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References
- Arctander, S. (1969). Perfume and Flavor Chemicals. Montclair, NJ.
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press.
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 623-36-9Physical Properties
| Molecular Weight | 98.14 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 1.4🔬 PubChem |
| Boiling Point | 138.7 °C🔬 EPA CompTox |
| Vapor Pressure | 6.0005 mmHg @ 25°C📊 OPERA |
| Flash Point | 29.5 °C🔬 EPA CompTox |
| Involatility Index | 0.6528💻 Calculated |
| log Kp (skin permeability) | -2.305💻 Calculated |
| SMILES | CCC=C(C)C=O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Moderate💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | greensweet• leffingwell |
| Functional Groups | aldehydealkene💻 RDKit |
| “Powerful and diffusive, "gassy"-green and slightly fruity odor of poor tenacity.”📖 Arctander | |
| 2-Methyl-2-pentenal has a powerful, grassy-green, slightly fruity odor.📖 Fenaroli | |
Flavor Notes (Arctander)
| “The title aldehyde has been synthesized mainly for the purpose of using it in reconstituting the aroma in dry Coffee extracts ("Instant Coffee") and in Onion flavors. However, the material forms only a minor part of the very complex and delicate aroma-picture of Coffee.”📖 Arctander |
Regulatory Status
| IFRA Listed | Yes — see IFRA Standards for category limits⚖️ IFRA 51 |
| IOFI Classification | Nature Identical📖 Fenaroli |
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: DTXSID3052301
Physical Properties
| Molecular Weight | 98.145 g/mol🔬 EPA CompTox |
| Density | 0.858 g/cm^3🔬 EPA CTX |
| Boiling Point | 136.862 °C🔬 EPA CTX |
| Melting Point | -94 °C🔬 EPA CTX |
| Flash Point | 30.533 °C🔬 EPA CTX |
| Refractive Index | 1.42 Dimensionless📊 OPERA |
| Molar Volume | 118.311 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.289 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 1.289 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.289 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.39 Log10 unitless📊 OPERA |
| Water Solubility | 0.116 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 7.598 mmHg🔬 EPA CTX |
| Viscosity | 0.51 cP📊 OPERA |
| Surface Tension | 24.305 dyn/cm📊 OPERA |
| Thermal Conductivity | 138.347 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 17.07 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 1 count💻 Computed |
| Rotatable Bonds | 2 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 29.933 cm^3/mol📊 OPERA |
| Polarizability | 11.867 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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