Citral (CAS 5392-40-5) — Citrus Top Note Fragrance Ingredient
Citral
CAS 5392-40-5
What Is Citral?
Citral is a bright, lemony fragrance molecule found naturally in citrus fruits and herbs like lemongrass. You’ll encounter it in citrus-scented cleaning products, perfumes, and lemon-flavored foods. This zesty ingredient matters because it creates that instant ‘fresh squeezed lemon’ impression in fragrances, while also serving as a building block for more complex citrus notes.
Safety Profile
USE WITH AWARENESS
What Does Citral Smell Like?
Citral bursts with piercing lemon intensity – imagine peeling a fresh Meyer lemon with that initial citrus spray. The top note is almost metallic in its brightness, like lemon zest rubbed between fingers. As it evolves, it reveals subtle herbal undertones reminiscent of lemongrass tea. The dry-down maintains a clean, slightly waxy citrus character, though less sweet than actual lemon oil. In blends, it provides a crisp, photorealistic lemon note that cuts through heavier ingredients.
Scent Profile
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Citral provides the electrifying citrus spark in this classic cologne, cutting through the herbal heart with photorealistic lemon zest.
Used alongside other citrus notes to create the fragrance’s signature ‘sun-drenched lemon grove’ opening accord.
Citral contributes to the unisex fragrance’s bright, clean citrus top notes that made it revolutionary in the 90s.
The citral-lemon verbena pairing creates a transparent citrus note that floats above the classic Guerlain base.
Citral helps recreate the traditional citrus bouquet that defines this historic cologne formula.
2D Molecular Structure
SMILES: CC(C)=CCCC(C)=CC=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Citral is an aldehyde terpenoid consisting of two isomers: geranial (citral A) and neral (citral B). It occurs naturally in citrus oils (up to 5% in lemon oil) and lemongrass (up to 85%). Industrial production typically involves synthesis from myrcene or via the citral process involving condensation of acetone with acetylene. The E/Z isomerism affects odor quality – geranial is sharper while neral is softer. Citral readily undergoes cyclization to form ionones and is a key intermediate in vitamin A synthesis.
Physical & Chemical Properties
| Boiling Point | 229 °C |
|---|---|
| Density | 0.889 g/cm³ |
| Refractive Index | 1.487-1.489 |
| Flash Point | 101 °C |
| Vapor Pressure | 0.01 mmHg at 20°C |
| Solubility | Slightly soluble in water, miscible with alcohol |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Citrus top note compositions |
| Functional Products | 0.1-0.5% | Up to 1% | Cleaning products, detergents |
| Flavors | 10-100 ppm | Up to 200 ppm | Lemon flavor profiles |
| Aromatherapy | 0.5-5% | Up to 10% | In blends with other citrus oils |
Classic Accords
+ Lavender + Oakmoss = Modern fougère
+ Ginger + Mint = Refreshing cologne
+ Verbena + Rosemary = Herbal citrus
Tip: Stabilize citral in alcohol bases with 0.1% BHT to prevent oxidation and discoloration.
Alternatives & Comparisons
Less sharp citrus note with rosy undertones, preferred when phototoxicity is a concern.
Modern captive with similar citrus character but improved stability and reduced sensitization potential.
When a less aggressive citrus note is needed that blends smoothly with woody notes.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. IFRA, REACH, EU Cosmetics Regulation standards update periodically. Consult current IFRA Standards Library before formulating. Not legal or regulatory advice.
IFRA Status
IFRA 49th Amendment restricts citral to 5% in leave-on products and 10% in rinse-off due to sensitization potential.
EU Allergen Declaration
Must be declared when present at ≥0.001% in leave-on products or ≥0.01% in rinse-off products (EU Regulation No 1223/2009).
GHS Classification
H317 May cause allergic skin reaction
H319 Eye irritation
RIFM Assessment
RIFM assessment confirms citral as a skin sensitizer with NOAEL of 250 mg/kg/day based on repeated dose toxicity studies.
Sustainability
Most commercial citral is synthesized from petrochemical sources, though natural extraction from lemongrass remains viable. The synthetic route has higher atom efficiency (85%) than early processes. Recent advances enable production from bio-based myrcene. Environmental impact is moderate due to biodegradability (80% in 28 days) and low bioaccumulation potential (log Kow 2.7).
Explore Citral
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Industry & Science Data
References
- Bauer et al. (2001). Common Fragrance and Flavor Materials. Wiley-VCH. ISBN 9783527616324
- IFRA Standards (2022). 49th Amendment. IFRA Standards
- PubChem Compound Summary for Citral CID 638011
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Mar 2026.
Ingredient Data Sheet
CAS 5392-40-5Physical Properties
| Molecular Weight | 152.23 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 3🔬 PubChem |
| Boiling Point | 228.9 °C🔬 EPA CompTox |
| Vapor Pressure | 5 mmHg @ 25°C📊 OPERA |
| Flash Point | 101.7 °C🔬 EPA CompTox |
| Involatility Index | 0.4368💻 Calculated |
| log Kp (skin permeability) | -1.499💻 Calculated |
Volatility & Performance
| Fragrance Note | Heart💻 Calculated |
| Volatility Class | Moderate💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | citrusfreshfruitylemon• leffingwell |
| “Widely used as a powerful Lemon-fragrance G. Floral-citrusy, delicate odor, very different CH8 from that of Citral.”📖 Arctander | |
| Citral has a strong, lemon-like odor and a characteristic bittersweet taste. Commercially, the product is a mixture of two geometric isomers — a-citral and b-citral, each exhibiting cis- and trans-isomers because of the position of the double bond.📖 Fenaroli | |
Sensory Thresholds
| Odor Detection Threshold | 0.1866 ppm (n=21)📖 van Gemert |
Regulatory Status
| IFRA Listed | Yes — see IFRA Standards for category limits⚖️ IFRA 51 |
| EU Annex III | Listed (restricted)⚖️ IFRA 51 |
| 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: DTXSID6024836
Physical Properties
| Molecular Weight | 152.237 g/mol🔬 EPA CompTox |
| Density | 0.891 g/cm^3🔬 EPA CTX |
| Boiling Point | 228 °C🔬 EPA CTX |
| Melting Point | -0.5 °C🔬 EPA CTX |
| Flash Point | 91.556 °C🔬 EPA CTX |
| Refractive Index | 1.457 Dimensionless📊 OPERA |
| Molar Volume | 177.753 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.76 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 3.058 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 3.058 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 5.01 Log10 unitless📊 OPERA |
| Water Solubility | 0.008 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 0.091 mmHg🔬 EPA CTX |
| Viscosity | 1.373 cP📊 OPERA |
| Surface Tension | 25.346 dyn/cm📊 OPERA |
| Thermal Conductivity | 133.582 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 | 4 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 48.365 cm^3/mol📊 OPERA |
| Polarizability | 19.174 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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