Paraldehyde (CAS 123-63-7) — Sweet N/A Note Fragrance Ingredient
Paraldehyde
CAS 123-63-7
What Is Paraldehyde?
Paraldehyde is a synthetic chemical primarily used in industrial applications and medical settings as a sedative. It’s rarely encountered in consumer products today. Historically, it was used in perfumery for its sharp, ethereal character. This ingredient matters as a cautionary example of how pharmaceutical chemicals were once repurposed in fragrance before modern safety standards.
Safety Profile
PROFESSIONAL USEWhat Does Paraldehyde Smell Like?
Paraldehyde assaults the senses with a piercing, medicinal sharpness reminiscent of hospital antiseptics. The initial blast carries metallic undertones and a volatile, almost electrical quality. As it settles, it reveals a strange fruity-etheric character like overripe apples preserved in rubbing alcohol. The dry-down leaves a lingering chemical bitterness that persists unnervingly on skin and fabric.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
2D Molecular Structure
SMILES: CC1OC(C)OC(C)O1
Chemistry, Properties & Perfumer Guide
The Chemistry
Paraldehyde is the cyclic trimer of acetaldehyde, forming a six-membered ring structure with three oxygen atoms. This unusual cyclic ether structure contributes to its high stability compared to acetaldehyde. Industrially produced through acid-catalyzed polymerization of acetaldehyde, its synthesis requires careful control to prevent decomposition back to the monomer. The molecule exists as a racemic mixture with no optical activity.
Physical & Chemical Properties
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|
Classic Accords
Tip: Not recommended for modern perfumery due to safety concerns.
Alternatives & Comparisons
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not listed in IFRA standards due to pharmaceutical classification.
GHS Classification
RIFM Assessment
No current RIFM evaluation due to pharmaceutical classification.
Sustainability
Paraldehyde production has significant environmental concerns due to acetaldehyde handling requirements and polymerization byproducts. As a pharmaceutical chemical with limited fragrance applications, it represents an obsolete material in modern sustainable perfumery.
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Ingredient Data Sheet
CAS 123-63-7Physical Properties
| Molecular Weight | 132.16 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 0.7🔬 PubChem |
| Boiling Point | 127.8 °C🔬 EPA CompTox |
| Vapor Pressure | 11 mmHg @ 25°C📊 OPERA |
| Flash Point | 35.6 °C🔬 EPA CompTox |
| Involatility Index | 1.0313💻 Calculated |
| log Kp (skin permeability) | -3.009💻 Calculated |
| SMILES | CC1OC(OC(O1)C)C🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Fast💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | fruityrumsweet• leffingwell |
| Functional Groups | ether💻 RDKit |
| Paraldehyde has a characteristic aromatic odor and warm, but disagreeable burning taste.📖 Fenaroli | |
Sensory Thresholds
| Odor Detection Threshold | 0.0224 ppm (n=2)📖 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: DTXSID9023419
Physical Properties
| Molecular Weight | 132.159 g/mol🔬 EPA CompTox |
| Density | 0.992 g/cm^3🔬 EPA CTX |
| Boiling Point | 124.763 °C🔬 EPA CTX |
| Melting Point | 12.439 °C🔬 EPA CTX |
| Flash Point | 34.969 °C🔬 EPA CTX |
| Refractive Index | 1.386 Dimensionless📊 OPERA |
| Molar Volume | 139.559 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 0.67 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 0.641 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 0.641 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.16 Log10 unitless📊 OPERA |
| Water Solubility | 0.865 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 13.184 mmHg🔬 EPA CTX |
| Viscosity | 1.21 cP📊 OPERA |
| Surface Tension | 24.596 dyn/cm📊 OPERA |
| Thermal Conductivity | 124.515 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 27.69 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 3 count💻 Computed |
| Rotatable Bonds | 0 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 32.775 cm^3/mol📊 OPERA |
| Polarizability | 12.993 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.
