Propyl 2-methylbutyrate (CAS 37064-20-3) — Sweet Top Note Fragrance Ingredient
Propyl 2-methylbutyrate
CAS 37064-20-3
What Is Propyl 2-methylbutyrate?
Propyl 2-methylbutyrate is a synthetic ester used in perfumery and food flavoring. It’s found in fruity fragrances and some processed foods. This ingredient matters because it provides a crisp, apple-like freshness that’s hard to replicate naturally, making it valuable for creating realistic fruit accords.
Safety Profile
GENERALLY SAFEWhat Does Propyl 2-methylbutyrate Smell Like?
Propyl 2-methylbutyrate bursts with a bright, juicy apple peel character that evolves into a deeper tropical fruitiness. The opening is all crisp green apple with a slightly tart edge, rounding out within minutes to reveal ripe banana and pineapple nuances. As it dries down, it maintains a clean, sweet fruitiness without becoming cloying, making it ideal for modern fruity-floral compositions. The dry-down reveals a faint woody undertone that prevents the fruit character from becoming one-dimensional.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used as the primary apple note in this youthful fragrance, providing realistic crispness without the sharpness of actual apple extracts.
Blends with passionfruit and mango notes to create a photorealistic tropical fruit basket effect in the heart notes.
2D Molecular Structure
SMILES: CCCOC(=O)C(C)CC
Chemistry, Properties & Perfumer Guide
The Chemistry
Propyl 2-methylbutyrate belongs to the ester class, synthesized through esterification of 2-methylbutyric acid with propanol. This branched-chain ester is valued for its stereochemistry – the chiral center at the 2-position creates more complex odor characteristics than straight-chain esters. Industrial production typically uses acid-catalyzed Fischer esterification under controlled conditions to maximize yield of the desired stereoisomer.
Physical & Chemical Properties
| Appearance | Colorless liquid |
|---|---|
| Boiling Point | ~150-160 °C (estimated) |
| Density | ~0.87 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Fruity top note component |
| Functional Fragrance | 0.1-0.5% | Up to 1% | Apple-themed products |
Classic Accords
Tip: Use with bergamot to brighten or with vanilla to sweeten fruity compositions.
Alternatives & Comparisons
More volatile with stronger green apple character, better for fleeting top notes.
Banana-like ester that can substitute when more tropical fruitiness is desired.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions currently apply to propyl 2-methylbutyrate.
RIFM Assessment
RIFM has evaluated propyl 2-methylbutyrate as safe for current fragrance use levels.
Sustainability
As a synthetic material, propyl 2-methylbutyrate has minimal environmental impact in production compared to natural fruit extracts. The synthesis uses renewable alcohol feedstocks and produces minimal waste. Its high potency means very small quantities are needed in formulations.
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781420090772
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 37064-20-3Physical Properties
| Molecular Weight | 144.21 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 2.4🔬 PubChem |
| Boiling Point | 158 °C🔬 EPA CompTox |
| Vapor Pressure | 3.397 mmHg @ 25°C📊 OPERA |
| Flash Point | 46.7 °C🔬 EPA CompTox |
| Involatility Index | 0.3049💻 Calculated |
| log Kp (skin permeability) | -1.876💻 Calculated |
| SMILES | CCCOC(=O)C(C)CC🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Moderate💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | applefruitygreenpineapplesweet• leffingwell |
| Functional Groups | esterether💻 RDKit |
Sensory Thresholds
| Odor Detection Threshold | 0.0002 ppm (n=3)📖 van Gemert |
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: DTXSID90865847
Physical Properties
| Molecular Weight | 144.214 g/mol🔬 EPA CompTox |
| Density | 0.88 g/cm^3📊 OPERA |
| Boiling Point | 156.284 °C📊 OPERA |
| Melting Point | -72.578 °C📊 OPERA |
| Flash Point | 46.496 °C📊 OPERA |
| Refractive Index | 1.411 Dimensionless📊 OPERA |
| Molar Volume | 164.448 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.48 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.48 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.48 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.94 Log10 unitless📊 OPERA |
| Water Solubility | 0.01 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 3.397 mmHg🔬 EPA CTX |
| Viscosity | 0.908 cP📊 OPERA |
| Surface Tension | 25.252 dyn/cm📊 OPERA |
| Thermal Conductivity | 131.666 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 26.3 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 2 count💻 Computed |
| Rotatable Bonds | 4 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 40.845 cm^3/mol📊 OPERA |
| Polarizability | 16.192 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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