Isobutyl 2-methylcrotonate (CAS 61692-84-0) — Sweet Top to middle Note Fragrance Ingredient
Isobutyl 2-methylcrotonate
CAS 61692-84-0
What Is Isobutyl 2-methylcrotonate?
Isobutyl 2-methylcrotonate is a synthetic fragrance ingredient used to add fruity, apple-like nuances to perfumes and scented products. You’ll encounter it in body sprays, candles, and household cleaners. This versatile molecule matters because it can mimic natural fruit aromas at a fraction of the cost, making everyday products smell more appealing without relying on expensive botanical extracts.
Safety Profile
GENERALLY SAFEWhat Does Isobutyl 2-methylcrotonate Smell Like?
Isobutyl 2-methylcrotonate bursts with a bright, crisp green apple top note that carries subtle tropical undertones of pineapple and banana. As it evolves, the scent becomes more candied, like apple Jolly Ranchers with a faint herbal edge. The dry-down reveals a clean, slightly woody character that prevents the fruitiness from becoming cloying. This molecule maintains remarkable tenacity for a fruity note, lingering on scent strips for hours while gradually softening into a pleasant, skin-like muskiness.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used as the core apple note in this photorealistic fragrance, where its crispness perfectly captures the tartness of Granny Smith apples with a cocktail twist.
Provides subtle fruity enhancement to the citrus top notes, adding dimension without overpowering the aquatic heart.
Blends with ethyl maltol to create the candy apple effect that defines this cult gourmand fragrance.
Works alongside other fruity esters to build the signature crisp apple note that made this fragrance iconic.
Contributes to the playful fruity opening that transitions into the white chocolate base.
2D Molecular Structure
SMILES: C\C=C(/C)C(=O)OCC(C)C
Chemistry, Properties & Perfumer Guide
The Chemistry
Isobutyl 2-methylcrotonate belongs to the ester class of organic compounds, specifically an isobutyl ester of 2-methylcrotonic acid. It’s synthesized through esterification reactions between isobutanol and 2-methylcrotonic acid, typically catalyzed by strong acids. The molecule features a branched alkyl chain that contributes to its volatility and fruity odor profile. While not found in nature, its structural analogs occur in various fruits, explaining why humans perceive its scent as familiar and pleasant.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | ~180-190 °C (estimated) |
| Density | ~0.87 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-3% | Up to 5% | Fruity top note component |
| Body Care | 0.1-1% | Up to 2% | Apple-like freshness |
| Household | 0.05-0.5% | Up to 1% | Clean fruity accents |
| Candles | 0.5-2% | Up to 3% | Heat-stable fruit note |
Classic Accords
Tip: Use with cooling agents like menthol derivatives to enhance the perception of crispness in apple-themed fragrances.
Alternatives & Comparisons
When a greener, less sweet apple character is needed, with better longevity in the heart phase.
For a more complex fruity profile that bridges apple and pear notes with tropical nuances.
Provides a stronger pineapple note that can complement the apple character in tropical compositions.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No restrictions under current IFRA standards (49th Amendment).
RIFM Assessment
Not currently evaluated as a standalone material by RIFM, but structurally similar esters have excellent safety profiles.
Sustainability
As a synthetic material, isobutyl 2-methylcrotonate offers consistent quality without agricultural land use. Production typically uses petrochemical feedstocks, though emerging bio-based routes could reduce environmental impact. Its high potency means low usage rates, minimizing ecological load compared to natural extracts requiring large harvest volumes.
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References
- Bauer, K. et al. (2001). Common Fragrance and Flavor Materials. Wiley-VCH. ISBN 978-3-527-30364-6
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID90886456
Physical Properties
| Molecular Weight | 156.225 g/mol🔬 EPA CompTox |
| Density | 0.902 g/cm^3📊 OPERA |
| Boiling Point | 184.799 °C📊 OPERA |
| Melting Point | -35.249 °C📊 OPERA |
| Flash Point | 65.322 °C📊 OPERA |
| Refractive Index | 1.434 Dimensionless📊 OPERA |
| Molar Volume | 174.371 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.979 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.979 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.979 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.43 Log10 unitless📊 OPERA |
| Water Solubility | 0.031 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.706 mmHg📊 OPERA |
| Surface Tension | 26.179 dyn/cm📊 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 | 45.379 cm^3/mol📊 OPERA |
| Polarizability | 17.99 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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