2,4-Hexadienyl isobutyrate (CAS 16491-24-0) — Sweet Top to middle Note Fragrance Ingredient
2,4-Hexadienyl isobutyrate
CAS 16491-24-0
What Is 2,4-Hexadienyl isobutyrate?
2,4-Hexadienyl isobutyrate is a synthetic fragrance ingredient used to add fruity, tropical notes to perfumes and scented products. It’s commonly found in body sprays, air fresheners, and tropical-themed fragrances. This ester compound matters because it provides a cost-effective way to create fresh, juicy fruit accords without using natural extracts, making fragrances more affordable and consistent in quality.
Safety Profile
GENERALLY SAFEWhat Does 2,4-Hexadienyl isobutyrate Smell Like?
2,4-Hexadienyl isobutyrate bursts with a lively, juicy fruit character reminiscent of ripe pineapple and strawberry jam. The opening is bright and slightly tart, like the first bite of a just-ripe mango, softening into a sweeter, creamier heart that suggests coconut milk and passionfruit. As it dries down, it maintains a pleasant fruity persistence without becoming cloying, leaving a clean, almost citrusy finish that makes it useful in fresh compositions. The overall effect is tropical yet balanced – more sophisticated than simple fruit notes but still immediately recognizable as a summer fragrance component.
2D Molecular Structure
SMILES: CC=CC=CCOC(=O)C(C)C
Chemistry, Properties & Perfumer Guide
The Chemistry
2,4-Hexadienyl isobutyrate is an ester formed from isobutyric acid and 2,4-hexadienol. As a synthetic molecule, it’s typically produced through acid-catalyzed esterification under controlled conditions. The conjugated diene system in the hexadienyl portion contributes to its reactivity and fruity character. Being wholly synthetic, it doesn’t occur in nature but was designed to mimic tropical fruit esters while offering greater stability and lower production costs than natural alternatives.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Odor Strength | Medium to strong |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Fruit accord booster |
| Body Care | 0.1-1% | Up to 3% | Shower gel freshness |
| Home Fragrance | 1-3% | Up to 7% | Tropical air fresheners |
Classic Accords
Tip: Use in small doses to brighten citrus top notes or in larger amounts for full tropical effects.
Alternatives & Comparisons
More apple-like fruit character with similar volatility, useful when a less tropical profile is desired.
Stronger pineapple note with better diffusion, though slightly more aggressive in character.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No current IFRA restrictions. Not listed in any amendment as of 2023.
RIFM Assessment
Not currently assessed by RIFM but considered low priority due to low volume of use.
Sustainability
As a fully synthetic material, 2,4-Hexadienyl isobutyrate has minimal environmental impact in production compared to natural extracts. Its synthesis from petrochemical feedstocks raises typical sustainability concerns of non-renewable sourcing, but its potency means very small quantities are needed in formulations. No known ecological toxicity issues at current usage levels.
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Ingredient Data Sheet
CAS 16491-24-0Physical Properties
| Molecular Weight | 168.23 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 2.7🔬 PubChem |
| Boiling Point | 218 °C🔬 EPA CompTox |
| Vapor Pressure | 0.2239 mmHg @ 25°C📊 OPERA |
| Flash Point | 85.5 °C🔬 EPA CompTox |
| Involatility Index | 0.0186💻 Calculated |
| log Kp (skin permeability) | -1.809💻 Calculated |
| SMILES | CC=CC=CCOC(=O)C(C)C🔬 PubChem |
Volatility & Performance
| Fragrance Note | Heart💻 Calculated |
| Volatility Class | Slow💻 Calculated |
| Persistence Score | 1.1 / 5💻 Calculated |
Odor & Flavor
| Functional Groups | esteretheralkene💻 RDKit |
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: DTXSID4047414
Physical Properties
| Molecular Weight | 168.236 g/mol🔬 EPA CompTox |
| Density | 0.904 g/cm^3🔬 EPA CTX |
| Boiling Point | 211.49 °C📊 OPERA |
| Melting Point | -59.454 °C📊 OPERA |
| Flash Point | 78.59 °C📊 OPERA |
| Refractive Index | 1.456 Dimensionless📊 OPERA |
| Molar Volume | 184.691 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 3.023 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 3.023 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 3.023 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.83 Log10 unitless📊 OPERA |
| Water Solubility | 0.007 mol/L📊 OPERA |
| Henry's Law Constant | 0.001 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.111 mmHg📊 OPERA |
| Viscosity | 1.348 cP📊 OPERA |
| Surface Tension | 26.608 dyn/cm📊 OPERA |
| Thermal Conductivity | 133.884 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 | 50.227 cm^3/mol📊 OPERA |
| Polarizability | 19.911 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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