Acetaldehyde (CAS 75-07-0) — Citrus Top Note Fragrance Ingredient
Acetaldehyde
CAS 75-07-0
What Is Acetaldehyde?
Acetaldehyde is a simple organic compound found naturally in ripe fruits, coffee, and bread. It’s also produced industrially and used in perfumery for its sharp, fruity-green character. This volatile molecule contributes to the fresh top notes of many fragrances, though it’s more commonly encountered as a byproduct of alcohol metabolism in the human body.
Safety Profile
USE WITH AWARENESSWhat Does Acetaldehyde Smell Like?
Acetaldehyde bursts forth with a piercing, green-apple sharpness that borders on metallic. The initial impression is intensely fruity – like overripe bananas crushed with cider vinegar – but quickly evolves into something more chemical and solvent-like. Within minutes, this volatile top note dissipates into a faint, slightly nutty aroma reminiscent of roasted coffee beans. Its dry-down leaves almost no trace, making it useful for creating fleeting freshness in fragrance openings.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used sparingly to enhance the citrusy freshness of the lemon top notes, creating a sparkling, almost effervescent quality that defines this classic cologne.
Contributes to the crisp green opening, pairing with violet leaf to create a dewy, freshly-cut grass effect before fading into the floral heart.
2D Molecular Structure
SMILES: CC=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Acetaldehyde (CH3CHO) is the simplest aldehyde after formaldehyde. This volatile organic compound occurs naturally through plant metabolism and fermentation processes. Industrially, it’s produced via ethylene oxidation or ethanol dehydrogenation. The molecule’s high reactivity stems from its carbonyl group, making it prone to polymerization and oxidation. In perfumery, stabilized forms are used to prevent rapid degradation.
Physical & Chemical Properties
| Boiling Point | 20.2 °C |
|---|---|
| Flash Point | -39 °C |
| Vapor Pressure | 740 mmHg at 20°C |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.01-0.1% | Up to 0.2% | IFRA restricted |
| Functional Fragrance | Not used | N/A | Generally avoided |
Classic Accords
Tip: Always use stabilized forms and incorporate into alcohol bases last to minimize degradation.
Alternatives & Comparisons
Provides similar green-fruity effects with greater stability and lower reactivity. Lacks acetaldehyde’s sharp metallic edge.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Restricted to 0.2% in leave-on products (IFRA Amendment 49). Prohibited in spray applications.
EU Allergen Declaration
Not listed as EU allergen
GHS Classification
RIFM Assessment
Classified as a potential sensitizer with recommended use limits based on dermal exposure risk.
Sustainability
Most acetaldehyde used in perfumery is synthetic, derived from petrochemical feedstocks. Some bio-based production methods exist using ethanol fermentation. Its high volatility contributes to VOC emissions, though rapid atmospheric degradation limits environmental persistence.
Explore Acetaldehyde
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References
- IFRA Standards (2023). Amendment 49 – Acetaldehyde. IFRA
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID5039224
Physical Properties
| Molecular Weight | 44.053 g/mol🔬 EPA CompTox |
| Density | 0.784 g/cm^3🔬 EPA CTX |
| Boiling Point | 20.502 °C🔬 EPA CTX |
| Melting Point | -124.296 °C🔬 EPA CTX |
| Flash Point | -37.43 °C🔬 EPA CTX |
| Refractive Index | 1.315 Dimensionless📊 OPERA |
| Molar Volume | 58.868 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | -0.128 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | -0.023 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | -0.023 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 1.79 Log10 unitless📊 OPERA |
| Water Solubility | 18.748 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 838.208 mmHg🔬 EPA CTX |
| Viscosity | 0.285 cP📊 OPERA |
| Surface Tension | 20.332 dyn/cm📊 OPERA |
| Thermal Conductivity | 149.31 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 | 0 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 11.501 cm^3/mol📊 OPERA |
| Polarizability | 4.56 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.
