4-Hydroxyacetophenone (CAS 99-93-4) — Sweet Middle Note Fragrance Ingredient
4-Hydroxyacetophenone
CAS 99-93-4
What Is 4-Hydroxyacetophenone?
4-Hydroxyacetophenone is a synthetic fragrance ingredient with a sweet, powdery, and slightly phenolic scent. It’s occasionally used in perfumes and cosmetics to add subtle floral nuances. This molecule matters because it serves as a building block for more complex fragrance materials and can contribute to powdery accords in fine fragrances.
Safety Profile
GENERALLY SAFEWhat Does 4-Hydroxyacetophenone Smell Like?
4-Hydroxyacetophenone presents a delicate balance of sweet powderiness with subtle phenolic undertones. The initial impression is reminiscent of heliotrope’s soft almond-like sweetness, evolving into a clean, slightly medicinal character. As it dries down, it reveals a persistent powdery note that blends well with floral and woody materials, behaving like a quiet supporting actor rather than a dominant note.
2D Molecular Structure
SMILES: CC(=O)C1=CC=C(O)C=C1
Chemistry, Properties & Perfumer Guide
The Chemistry
4-Hydroxyacetophenone is a simple phenolic ketone with the molecular formula C8H8O2. It’s synthesized through Friedel-Crafts acylation of phenol or through oxidation of 4-ethylphenol. The hydroxyl group at the para position makes it moderately polar, influencing both its solubility and odor characteristics. While not chiral itself, it serves as a precursor to various chiral fragrance molecules.
Physical & Chemical Properties
| Melting Point | 109-112 °C |
|---|---|
| Boiling Point | 296 °C |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Powdery floral modifier |
| Cosmetics | 0.1-1% | Up to 3% | Background note |
Classic Accords
Tip: Use sparingly in floral compositions to enhance powdery aspects without overwhelming the blend.
Alternatives & Comparisons
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions apply to 4-hydroxyacetophenone.
RIFM Assessment
Limited RIFM assessment available due to low usage volume.
Sustainability
As a synthetic material, 4-hydroxyacetophenone has minimal environmental impact in production. Its synthesis from phenol derivatives is well-established with good atom economy. Being produced in controlled industrial settings reduces ecological concerns compared to some natural extracts.
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References
- PubChem Compound Summary for 4-Hydroxyacetophenone PubChem CID 7468
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID0029133
Physical Properties
| Molecular Weight | 136.15 g/mol🔬 EPA CompTox |
| Density | 1.27 g/cm^3🔬 EPA CTX |
| Boiling Point | 281.333 °C📊 OPERA |
| Melting Point | 108.519 °C🔬 EPA CTX |
| Flash Point | 121.3 °C🔬 EPA CTX |
| Refractive Index | 1.552 Dimensionless📊 OPERA |
| Molar Volume | 119.394 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.366 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 1.51 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.413 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 7.78 Log10 unitless📊 OPERA |
| Water Solubility | 0.073 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.003 mmHg🔬 EPA CTX |
| Viscosity | 7.316 cP📊 OPERA |
| Surface Tension | 42.075 dyn/cm📊 OPERA |
| Thermal Conductivity | 151.682 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 37.3 Ų💻 Computed |
| H-Bond Donors | 1 count💻 Computed |
| H-Bond Acceptors | 2 count💻 Computed |
| Rotatable Bonds | 1 count💻 Computed |
| Aromatic Rings | 1 count💻 Computed |
| Molar Refractivity | 38.162 cm^3/mol📊 OPERA |
| Polarizability | 15.129 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.
