2-Methylpentanal (CAS 123-15-9) — Green Top Note Fragrance Ingredient
2-Methylpentanal
CAS 123-15-9
What Is 2-Methylpentanal?
2-Methylpentanal is a synthetic fragrance ingredient with a distinctive green, leafy aroma. You’ll encounter it in perfumes, especially those aiming for fresh, natural green notes. This aldehyde matters because it can mimic the crispness of crushed leaves or unripe fruit at minute concentrations, adding realism to nature-inspired fragrances.
Safety Profile
USE WITH AWARENESSWhat Does 2-Methylpentanal Smell Like?
2-Methylpentanal bursts with an intensely green, almost aggressive top note reminiscent of freshly torn grass blades and broken tomato vines. The initial sharpness mellows into a cucumber-like watery freshness, with subtle undertones of unripe apples. In drydown, it leaves a faint waxy-green trail, behaving like a more tenacious version of leaf alcohol but with greater diffusion.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used to amplify the hyper-realistic crushed galbanum effect, contributing razor-sharp greenness that defines this legendary chypre’s opening.
Provides the wet vegetal accent that mimics monsoon-drenched foliage, blending with ginger and cardamom for a rain-soaked garden effect.
2D Molecular Structure
SMILES: CCCC(C)C=O
Chemistry, Properties & Perfumer Guide
The Chemistry
2-Methylpentanal is a branched-chain aldehyde (C6H12O) produced industrially via hydroformylation of 2-methyl-1-pentene. Its structure features an α-branch that intensifies green character compared to linear hexanal. The molecule exists as enantiomers, with the (R)-form showing greater olfactory potency. Synthesis typically employs rhodium catalysts under controlled pressure, yielding material with <1% residual olefin content.
Physical & Chemical Properties
| Boiling Point | 130-132 °C |
|---|---|
| Vapor Pressure | 12.3 mmHg at 25°C |
| Density | 0.815 g/cm³ |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Powerful green modifier |
| Functional Fragrance | 0.01-0.1% | Up to 0.2% | Freshness booster in detergents |
Classic Accords
Tip: Stabilize in ethanol before adding to water-based systems to prevent aldehyde polymerization.
Alternatives & Comparisons
Less intense linear version for softer green effects, preferred in food flavors and delicate floral compositions.
More transient but extremely natural ‘cut grass’ note, suitable for top note bursts in naturalistic fragrances.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No specific restrictions under IFRA 51st Amendment. General aldehyde precautions apply.
GHS Classification
RIFM Assessment
RIFM assessment complete (2019). Safe at current industry usage levels with recommended concentration limits.
Sustainability
Synthesized from petrochemical feedstocks but used at extremely low doses (typically <0.1%). Production employs efficient catalytic processes with >90% atom economy. No known ecological accumulation due to rapid atmospheric degradation (half-life <24h).
Explore 2-Methylpentanal
Browse essential oils and aroma compounds.
Browse on iHerb →Affiliate disclosure: we may earn a small commission at no extra cost to you.
References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781439810743
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID9021978
Physical Properties
| Molecular Weight | 100.161 g/mol🔬 EPA CompTox |
| Density | 0.811 g/cm^3🔬 EPA CTX |
| Boiling Point | 117.988 °C🔬 EPA CTX |
| Melting Point | -100 °C🔬 EPA CTX |
| Flash Point | 18.522 °C🔬 EPA CTX |
| Refractive Index | 1.394 Dimensionless📊 OPERA |
| Molar Volume | 125.271 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.8 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 1.693 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.693 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.53 Log10 unitless📊 OPERA |
| Water Solubility | 0.042 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 19.617 mmHg🔬 EPA CTX |
| Viscosity | 0.571 cP📊 OPERA |
| Surface Tension | 23.811 dyn/cm📊 OPERA |
| Thermal Conductivity | 137.043 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 | 3 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 29.992 cm^3/mol📊 OPERA |
| Polarizability | 11.89 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.
