Isobutyl propionate (CAS 540-42-1) — Sweet Top Note Fragrance Ingredient
Isobutyl propionate
CAS 540-42-1
What Is Isobutyl propionate?
Isobutyl propionate is a synthetic ester commonly used in fruit-flavored products and perfumes. You’ll encounter it in candies, baked goods, and fragrances aiming for a juicy, ripe fruit effect. This ingredient matters because it delivers a crisp, natural-smelling fruitiness without relying on actual fruit extracts, making it versatile for both food and fragrance applications where consistency and shelf stability are important.
Safety Profile
GENERALLY SAFEWhat Does Isobutyl propionate Smell Like?
Isobutyl propionate bursts with the crisp sweetness of freshly cut pineapple and ripe Bartlett pears. The opening is all effervescent fruit salad – think juicy apples dipped in light syrup with a subtle green banana peel nuance. As it dries down, the sweetness softens into a creamy, almost rum-like warmth with faint floral undertones reminiscent of apple blossoms. The dry-down maintains a clean, slightly waxy fruit character that blends beautifully with other esters without becoming cloying.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to amplify the green tomato leaf accord with its crisp fruity facets, creating a dewy garden effect that bridges herbal and fruity elements seamlessly.
Provides the juicy mango top note illusion, blending with grapefruit and green notes to create the perfume’s signature sun-ripened fruit basket effect.
2D Molecular Structure
SMILES: CCC(=O)OCC(C)C
Chemistry, Properties & Perfumer Guide
The Chemistry
Isobutyl propionate belongs to the ester class, formed through esterification of propionic acid with isobutanol. Industrially, it’s synthesized via acid-catalyzed Fischer esterification. The molecule features a branched alkyl group (isobutyl) that contributes to its volatility and fruity character. Unlike straight-chain esters, the branching creates steric hindrance that affects both odor properties and hydrolysis resistance. While naturally occurring in some fruits at trace levels, commercial production is exclusively synthetic due to cost efficiency and purity requirements for fragrance applications.
Physical & Chemical Properties
| Boiling Point | 137-139 °C |
|---|---|
| Density | 0.869 g/cm³ at 20°C |
| Refractive Index | 1.397-1.399 |
| Flash Point | 33 °C (closed cup) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Fruity top note enhancer |
| Functional Fragrance | 1-3% | Up to 10% | Soap and detergent fruity notes |
| Flavor | 10-50 ppm | 5-100 ppm | Fruit flavor compositions |
Classic Accords
Tip: Use with citrus oils to extend their fruity character without the harshness of higher-boiling esters.
Alternatives & Comparisons
More banana-like character, useful when a heavier, more candied fruit effect is desired.
Stronger pineapple note with more diffusion, better for top-heavy compositions needing projection.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not restricted under current IFRA standards (Amendment 49).
GHS Classification
RIFM Assessment
Evaluated by RIFM in 2015 (FEMA 2212) with no safety concerns at current usage levels.
Sustainability
As a synthetic material, isobutyl propionate has minimal environmental impact in production. The petrochemical feedstocks are common industrial intermediates with established supply chains. Unlike natural fruit extracts, its production doesn’t compete with food crops and offers consistent quality year-round. The ester’s relatively simple structure makes it readily biodegradable under standard OECD test conditions.
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781420090772
- Arctander, S. (1969). Perfume and Flavor Chemicals. Allured Publishing. ASIN B0006BX4V4
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID8060240
Physical Properties
| Molecular Weight | 130.187 g/mol🔬 EPA CompTox |
| Density | 0.862 g/cm^3🔬 EPA CTX |
| Boiling Point | 137 °C🔬 EPA CTX |
| Melting Point | -71.4 °C🔬 EPA CTX |
| Flash Point | 36.538 °C🔬 EPA CTX |
| Refractive Index | 1.404 Dimensionless📊 OPERA |
| Molar Volume | 147.942 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.093 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.093 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.093 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.89 Log10 unitless📊 OPERA |
| Water Solubility | 0.013 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0.001 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 6.499 mmHg🔬 EPA CTX |
| Viscosity | 0.762 cP📊 OPERA |
| Surface Tension | 24.823 dyn/cm📊 OPERA |
| Thermal Conductivity | 129.547 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 | 3 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 36.212 cm^3/mol📊 OPERA |
| Polarizability | 14.356 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.
