Isobutyraldehyde (CAS 78-84-2) — Green Top Note Fragrance Ingredient
Isobutyraldehyde
CAS 78-84-2
What Is Isobutyraldehyde?
Isobutyraldehyde is a synthetic chemical used in perfumery to create fruity, green, and malty notes. You’ll encounter it in fragrances that aim for a crisp, slightly fermented apple character. This aldehyde matters because it adds a distinctive ‘sparkling’ top note effect, often used to create modern fruity-floral compositions with an unexpected twist.
Safety Profile
USE WITH AWARENESSWhat Does Isobutyraldehyde Smell Like?
Isobutyraldehyde bursts forth with a sharp, pungent greenness reminiscent of unripe apples and malt liquor. The initial blast quickly settles into a fermented fruit character – imagine cider apples meeting pear drops with a metallic edge. As it evolves, a peculiar nutty-malty nuance emerges, like toasted barley in whiskey production. The dry-down reveals a faintly sweet, hay-like quality that lingers surprisingly long for such a volatile material.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used sparingly here to amplify the crisp violet leaf and citrus opening, contributing to that legendary ‘sparkling green’ effect that defines this fougère masterpiece.
Provides a fleeting fermented fruit nuance that complements the citrus-herbal structure, adding modernity to this classic cologne structure.
2D Molecular Structure
SMILES: CC(C)C=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Isobutyraldehyde (2-methylpropanal) is a branched-chain aldehyde belonging to the same chemical family as formaldehyde but with markedly different properties. Industrially produced via hydroformylation of propene, this volatile compound exists as a colorless liquid. Its reactivity makes it valuable as a chemical intermediate. The branched structure reduces its water solubility compared to straight-chain aldehydes while increasing its stability against polymerization.
Physical & Chemical Properties
| Boiling Point | 63-65 °C |
|---|---|
| Flash Point | -19 °C |
| Density | 0.793 g/cm³ |
| Vapor Pressure | 160 mmHg at 20°C |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Used as top note modifier |
| Functional Fragrance | 0.01-0.1% | Up to 0.2% | Restricted due to potency |
Classic Accords
Tip: Always pre-dilute to 10% in ethanol before blending due to extreme volatility and potency.
Alternatives & Comparisons
Offers similar fermented fruit character but with more pronounced malty/yeasty nuances and slightly better stability in blends.
Provides greener apple character without the fermented aspect, preferred for fresher compositions.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No specific restrictions under current IFRA standards (49th Amendment).
EU Allergen Declaration
Not listed as EU allergen.
GHS Classification
RIFM Assessment
RIFM evaluation confirms safe use at current industry levels with proper handling precautions.
Sustainability
As a petrochemical derivative, isobutyraldehyde’s environmental impact stems from its production process. Modern catalytic hydroformylation methods have reduced energy requirements. Some fragrance houses are exploring bio-based routes using fermentation-derived precursors to improve sustainability profiles.
Explore Isobutyraldehyde
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781420090869
- IFRA Standards Library (2023). 49th Amendment. IFRA
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 78-84-2Physical Properties
| Molecular Weight | 72.11 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 0.8🔬 PubChem |
| Boiling Point | 63.9 °C🔬 EPA CompTox |
| Vapor Pressure | 170 mmHg @ 25°C📊 OPERA |
| Flash Point | -40 °C🔬 EPA CompTox |
| Involatility Index | 21.5764💻 Calculated |
| log Kp (skin permeability) | -2.572💻 Calculated |
| SMILES | CC(C)C=O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Very fast💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | bananachocolatefruitygreen• leffingwell |
| Functional Groups | aldehyde💻 RDKit |
| “Extremely diffusive, penetrating odor, pungent and - undiluted - unpleasant, sour, repulsive. In extreme dilution it becomes almost pleasant, fruity, Banana-like, "overripe fruit-like". Overall more pleasant than the n-Butyraldehyde.”📖 Arctander | |
| Isobutyraldehyde has a characteristic sharp, pungent odor.📖 Fenaroli | |
Flavor Notes (Arctander)
| “Widely used (in traces) in flavor compositions for imitation Banana, Berry, Butter, Caramel, Fruit, Liquor, Wine, Whisky and other flavors. See also comments under n-Butyraldehyde about mixtures with other flavor materials.”📖 Arctander |
Sensory Thresholds
| Odor Detection Threshold | 0.0123 ppm (n=9)📖 van Gemert |
Regulatory Status
| FEMA Number | FEMA 2220⚖️ FEMA GRAS |
| GRAS Status | Generally Recognized as Safe⚖️ FEMA GRAS |
| IOFI Classification | Nature Identical📖 Fenaroli |
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: DTXSID9021635
Physical Properties
| Molecular Weight | 72.107 g/mol🔬 EPA CompTox |
| Density | 0.79 g/cm^3🔬 EPA CTX |
| Boiling Point | 63.161 °C🔬 EPA CTX |
| Melting Point | -65.31 °C🔬 EPA CTX |
| Flash Point | -22.85 °C🔬 EPA CTX |
| Refractive Index | 1.367 Dimensionless📊 OPERA |
| Molar Volume | 92.258 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 0.85 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 0.786 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 0.786 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 2.47 Log10 unitless📊 OPERA |
| Water Solubility | 1.124 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 163.906 mmHg🔬 EPA CTX |
| Viscosity | 0.401 cP📊 OPERA |
| Surface Tension | 22.13 dyn/cm📊 OPERA |
| Thermal Conductivity | 139.334 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 17.07 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 1 count💻 Computed |
| Rotatable Bonds | 1 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 20.726 cm^3/mol📊 OPERA |
| Polarizability | 8.216 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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