Butyl 2-methylcrotonate (Z) (CAS 7785-64-0) — Sweet Top to middle Note Fragrance Ingredient
Butyl 2-methylcrotonate (Z)
CAS 7785-64-0
What Is Butyl 2-methylcrotonate (Z)?
Butyl 2-methylcrotonate (Z) is a synthetic fragrance ingredient used to create fruity, tropical nuances in perfumes and scented products. You’ll encounter it in summer fragrances, body sprays, and fruity-floral compositions. This ester matters because it adds a juicy, slightly green character that mimics ripe tropical fruits without being overly sweet, making it versatile for modern fragrance designs.
Safety Profile
GENERALLY SAFEWhat Does Butyl 2-methylcrotonate (Z) Smell Like?
Butyl 2-methylcrotonate (Z) bursts with a vibrant, tropical fruit character reminiscent of passionfruit and mango skins with a subtle green undertone. The opening is juicy and slightly tart, evolving into a smoother, rounded fruitiness that avoids cloying sweetness. In drydown, it leaves a clean, slightly woody-frucy trace that blends well with floral and citrus notes. The (Z)-configuration gives it a brighter, more naturalistic quality compared to its (E)-isomer.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used as the core tropical fruit accord, providing authentic passionfruit nuances without synthetic candy-like effects. Blends with jasmine and coconut for a beachy vibe.
Adds juicy depth to the top notes alongside bergamot and pink pepper. The green facet prevents the citrus from turning too sharp.
2D Molecular Structure
SMILES: CCCCOC(=O)C(\C)=C/C
Chemistry, Properties & Perfumer Guide
The Chemistry
Butyl 2-methylcrotonate (Z) is an unsaturated ester belonging to the crotonate family. The (Z)-configuration (cis arrangement) around the double bond gives it distinct odor properties compared to the (E)-isomer. Synthesized via esterification of 2-methylcrotonic acid with butanol under acidic conditions, often using zeolite catalysts for improved (Z)-selectivity. The molecule’s flexibility and moderate polarity make it versatile in both polar and non-polar fragrance bases.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | ~190-200°C (estimated) |
| Density | ~0.88 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Fruity top note modifier |
| Body Care | 0.1-0.5% | Up to 1% | Adds tropical character |
Classic Accords
Tip: Use with citrus oils to create dynamic fruity openings that don’t turn candied.
Alternatives & Comparisons
Shorter ester with brighter, more volatile fruity character. Better for fleeting top notes.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions currently apply to this material.
RIFM Assessment
Not currently evaluated by RIFM. Limited toxicological data available.
Sustainability
Synthetic production allows consistent quality without agricultural inputs. The manufacturing process has moderate energy requirements but no known hazardous byproducts. Being petroleum-derived, it’s not biodegradable but used at very low levels in formulations.
Explore Butyl 2-methylcrotonate (Z)
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References
- Bauer et al. (2001). Fruit Esters in Modern Perfumery. Perfumer & Flavorist.
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 7785-64-0Physical Properties
| Molecular Weight | 138.25 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 4.8🔬 PubChem |
| Boiling Point | 191.7 °C🔬 EPA CompTox |
| Vapor Pressure | 0.1456 mmHg @ 25°C📊 OPERA |
| Flash Point | 73.3 °C🔬 EPA CompTox |
| Involatility Index | 0.0134💻 Calculated |
| log Kp (skin permeability) | -0.135💻 Calculated |
| SMILES | CCCCC(=C)C(=CC)C🔬 PubChem |
Volatility & Performance
| Fragrance Note | Heart💻 Calculated |
| Volatility Class | Slow💻 Calculated |
| Persistence Score | 1.7 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | citrussweet• leffingwell |
| Functional Groups | alkene💻 RDKit |
Sensory Thresholds
| Odor Detection Threshold | 0.013 ppm📖 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: DTXSID2052526
Physical Properties
| Molecular Weight | 156.225 g/mol🔬 EPA CompTox |
| Density | 0.914 g/cm^3📊 OPERA |
| Boiling Point | 191.712 °C📊 OPERA |
| Melting Point | 10.715 °C📊 OPERA |
| Flash Point | 73.283 °C📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.296 dimensionless💻 Computed |
| Water Solubility | 0.042 mol/L📊 OPERA |
Transport Properties
| Vapor Pressure | 0.146 mmHg📊 OPERA |
| Surface Tension | 26.993 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 | 4 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 48.1 cm^3/mol💻 Computed |
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.
