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Aldehydes

Q: Is Aldehydes natural or synthetic?

. Extraction: All perfumery-grade aliphatic aldehydes are produced synthetically. Two industrial routes dominate: (1) Hydroformylation (the oxo process) — terminal alkenes react with syngas (CO + H2) over cobalt or rhodium catalysts at 85–200°C and 18–300 bar, yielding the corresponding aldehyde with one additional carbon. Rhodium-phosphine catalysts (developed 1970s onward) operate at lower pressures and give higher linear-to-branched selectivity. (2) Catalytic oxidation or dehydrogenation of primary alcohols — e.g., 1-decanol to decanal over copper or silver catalysts at 300–400°C. Some shorter-chain aldehydes occur naturally in citrus oils — decanal is found at 0.1–0.5% in sweet orange peel oil, nonanal in trace amounts — but commercial supply is entirely synthetic for consistency, purity, and cost. 2-Methylundecanal was first synthesised in 1904 by Georges Darzens via the glycidic ester condensation that bears his name..

POPULAR AND WEIRD / fresh · citrus · fruity

Aldehydes

Category	POPULAR AND WEIRD
Subcategory	fresh · citrus · fruity
Origin
Volatility	Top Note
Botanical	N/A — both synthetic and naturally occurring class of organic compounds
Appearance	Colorless to pale yellow clear liquid
Odor Strength	High
Producing Countries	Manufactured globally
Pyramid	Top

Blown-out candle wax, ironed linen, a metallic spark that lifts everything around it. Aldehydes are not one smell but a chemical series — C-8 through C-13 — each member distinct, all sharing that waxy, soapy, almost electric transparency that makes a composition feel radiant rather than grounded.

Scent
The Full Story
Fun Fact
Extraction & Chemistry
In Perfumery

Scent

The short-chain members (C-8, C-9) hit as sharp orange-zest brightness — pure citrus rind without sweetness. At C-10, the character shifts: still citrusy but now with a waxy, candle-tallow warmth underneath. C-11 is where the "aldehydic" archetype lives — clean, soapy, laundry-line freshness, the smell most people associate with the word. C-12 lauric is heavier, fattier, soapier, with a powdery spread that in extreme diluti on turns violet-like. C-12 MNA (2-methylundecanal) is the outlier: metallic, sparkling, amber-tinged, with a coumarinic drydown. Compared to musks, which soften and cushi on, aldehydes electrify. Compared to ozonic notes, which chill, aldehydes warm. At high concentration, the waxy-candle quality dominates; at trace levels, they become invisible architecture — structure without smell.

Evolution over time

Immediately

Sparkling, waxy, metallic effervescence — sharp citrus-candle wax brightness with soapy transparency

After a few hours

Waxy-candle sharpness fades; soapy, powdery, clean-linen character persists; C-12 MNA leaves a faint coumarinic-amber trail

After a few days

Short-chain members (C-8 to C-10) fully evaporated within hours. C-11 and C-12 lauric leave a faint waxy-soapy residue on fabric. C-12 MNA, the most substantive (388 hours per TGSC), retains a faint metallic-amber whisper

The Full Story

Aldehydes in perfumery refers principally to a small group of fatty long-chain aliphatic aldehydes — C-8 (octanal, CAS 124-13-0), C-9 (nonanal), C-10 (decanal, CAS 112-31-2), C-11 (undecanal), C-12 (dodecanal lauric, CAS 112-54-9) and C-12 MNA (methyl nonyl acetaldehyde) — that introduced a particular metallic-soapy-fatty-waxy character to twentieth-century perfumery. The 'aldehydic' note that defines Chanel No 5 (1921) [A] is principally this family.

This note in Première Peau. Gravitas Capitale. Sample all seven extraits in the Discovery Set.

Beyond the fatty aldehydes

Chemically, aldehyde simply means R-CHO (an aldehyde functional group), and many other perfumery materials are aldehydes by chemistry: vanillin, cinnamaldehyde, citral, hydroxycitronellal, benzaldehyde. But 'aldehydic' as a perfumery note refers specifically to the fatty C-8 to C-12 family. The historical breakthrough was the synthesis of these aldehydes in commercial purity in the early twentieth century — Ernest Beaux's use of them at the previously impossible 1% in Chanel No 5 is the canonical example.

Sources & Notes

[A] Beaux, E. (1921) — the formulation work behind Chanel No 5. See: Edwards, M., 'Perfume Legends.' The aldehyde fraction (C-10, C-11, C-12) at 1% concentration was unprecedented for the era.

Did You Know?

Did you know?

The naming convention for perfumery aldehydes is notoriously confusing. Aldehyde C-12 MNA (2-methylundecanal) has only 11 carbon atoms in its main chain — the C-12 designation counts the total carbons including the methyl branch. Meanwhile, Aldehyde C-12 Lauric (dodecanal) is a completely different molecule with a straight 12-carbon chain. A perfumer asking for 'C-12' without specifying 'lauric' or 'MNA' could receive either one — and they smell nothing alike.

Extraction & Chemistry

Extraction method: All perfumery-grade aliphatic aldehydes are produced synthetically. Two industrial routes dominate: (1) Hydroformylation (the oxo process) — terminal alkenes react with syngas (CO + H2) over cobalt or rhodium catalysts at 85–200°C and 18–300 bar, yielding the corresponding aldehyde with one additional carbon. Rhodium-phosphine catalysts (developed 1970s onward) operate at lower pressures and give higher linear-to-branched selectivity. (2) Catalytic oxidation or dehydrogenation of primary alcohols — e.g., 1-decanol to decanal over copper or silver catalysts at 300–400°C. Some shorter-chain aldehydes occur naturally in citrus oils — decanal is found at 0.1–0.5% in sweet orange peel oil, nonanal in trace amounts — but commercial supply is entirely synthetic for consistency, purity, and cost. 2-Methylundecanal was first synthesised in 1904 by Georges Darzens via the glycidic ester condensation that bears his name.

Molecular Formula	General formula: R-CHO — perfumery aldehydes range from C₈H₁₆O to C₁₄H₂₈O
CAS Number	Class of compounds. Key CAS numbers: octanal C-8 (124-13-0), nonanal C-9 (124-19-6), decanal C-10 (112-31-2), undecanal C-11 (112-44-7), dodecanal C-12 lauric (112-54-9), 2-methylundecanal C-12 MNA (110-41-8)
Botanical Name	N/A — both synthetic and naturally occurring class of organic compounds
IFRA Status	Restricted. Individual limits per IFRA/RIFM: decanal max 1% in fragrance concentrate, undecanal max 1%, dodecanal max 2%, 2-methylundecanal max 2%. C-12 MNA (2-methylundecanal) is classified as a skin sensitiser (GHS Cat. 1, H317) and is an EU-listed fragrance allergen requiring label declaration above 0.001% in leave-on products (Regulation 1223/2009, Annex III).
Synonyms	ALDEHYDE · ALIPHATIC ALDEHYDE · AROMATIC ALDEHYDE
Physical Properties
Odor Strength	High
Lasting Power	Varies by chain length: C-8 ~7 hours, C-11 ~72 hours, C-12 lauric ~368 hours, C-12 MNA ~388 hours (TGSC data at 100%)
Appearance	Colorless to pale yellow clear liquid

In Perfumery

Top-note amplifiers, diffusion boosters, and transparency agents. Aliphatic aldehydes (C-8 through C-13) function as olfactory highlighters — they project the heart outward and make surrounding materials brighter and more radiant. Key members and their CAS numbers: octanal (C-8, 124-13-0, orange-peel sharpness), nonanal (C-9, 124-19-6, waxy-citrus-rose), decanal (C-10, 112-31-2, sweet waxy orange-rind), undecanal (C-11, 112-44-7, fresh linen clarity), dodecanal (C-12 lauric, 112-54-9, soapy-waxy-fatty diffusion), and 2-methylundecanal (C-12 MNA, 110-41-8, metallic amber sparkle). Even in compositions not marketed as aldehydic, trace amounts of C-11 or C-12 are routinely dosed at 0.01–0.1% for lift and projection. The aldehydic-floral family — built on overdosed C-10, C-11, and C-12 MNA — defined 20th-century feminine perfumery. Aldehydes also appear in chypre, fougère, and powdery-amber constructions. 2-Methylundecanal is classified as a skin sensitiser (GHS Category 1, H317) and is an EU-listed fragrance allergen requiring declaration above 0.001% in leave-on cosmetic products.