Colorless to pale yellow liquid with green, floral, aldehydic odor
Odor Strength
High
Producing Countries
Manufactured globally
Pyramid
Top
Crushed ivy on a wet stone wall. A green so sharp it borders on metallic — leaf stems, lemon cortex, the aldehydic snap of freshly cut grass. At full strength it is aggressive; diluted to 1%, it becomes the most convincing green note in the perfumer's palette.
Immediately, intensely green — leaf stems snapped in half, lemon peel scraped against its white pith, the sharp vegetal brightness of crushed ivy. An aldehydic bite sits on top: metallic, almost chemical in the first seconds, then resolving into a tart, herbaceous freshness. Underneath, a faint floral-waxy suggestion, barely perceptible, that recalls privet blossoms in midsummer.
Compared to cis-3-hexenol (which smells of cut grass with a wet, juicy character), this molecule is drier, more angular, and more aldehydic. Compared to galbanum resinoid (which is green but heavy, rubbery, and balsamic), it is transparent and lifts rather than sits. Compared to violet leaf absolute (dense, fatty, cucumber-like), it is sharper and less rounded. The closest natural analogue may be the smell of tearing a privet leaf between your fingers — green, slightly bitter, with a faint metallic edge.
Evolution over time
Immediately
Immediately
Sharp, almost aggressive green-aldehydic attack. Crushed ivy stems, lemon cortex, wet metal. A tart, herbaceous brightness that fills the nose completely — the molecule announces itself before you bring the strip close.
After a few hours
After a few hours
The metallic aldehyde softens. A waxy, slightly floral green emerges — privet leaf, cucumber skin, a faint soapy undertone. Still distinctly green, but rounder, less caustic. The tart citrus-peel facet persists as a background note.
After a few days
After a few days
A pale, clean, faintly woody-green residue. The aldehyde is spent. What remains is a dry leaf-like trace, barely perceptible — moderate tenacity for a top note (8-24 hours depending on substrate).
The Full Story
2,4-Dimethylcyclohex-3-ene-1-carbaldehyde (CAS 68039-49-6, MW 138.21 g/mol) is a cyclic aldehyde synthesised by a single-step Diels-Alder reaction: 2-methyl-1,3-pentadiene reacts with acrolein at 45-75°C under moderate pressure (0.1-0.5 MPa), followed by aging at 70-100°C for two to six hours. The product is a roughly equal mixture of cis- and trans-isomers, both olfactively useful. Colorless to pale yellow liquid. Density 0.932-0.940 at 25°C. Boiling point 196°C at 760 mmHg. LogP 2.34.
The odor is intensely green and aldehydic — sharper than galbanum, more structured than cis-3-hexenol, less vegetal than violet leaf absolute. The character is often described as ivy leaf, privet hedge, and lemon cortex — a crisp, tart greenness with a metallic backbone. At high concentration it smells almost caustic; below 1% it delivers a notably natural green-leaf impression. The non-proprietary name Ligustral references the privet genus (Ligustrum), whose crushed leaves share the molecule's green-aldehydic signature.
The molecule's strength is high — evaluation at neat concentration is overwhelming, and a 10% dilution in dipropylene glycol is the standard starting point for smelling strips. Substantivity is moderate: 8 hours at full concentration on a blotter, extending to roughly 24 hours under occlusion. This positions it as a top-note material with enough tenacity to bridge into the heart, particularly when anchored by heavier green materials or woody fixatives.
IFRA restricts dimethylcyclohex-3-ene-1-carbaldehyde (all isomers combined) due to dermal sensitisation potential. The maximum permitted concentration in fine fragrance (Category 4) is 2.5% of the finished product. In practice, perfumers rarely exceed 0.5-1% in fine fragrance formulas — the molecule is potent enough to anchor a green accord at fractions of a percent.
The non-proprietary name Ligustral derives from the privet genus Ligustrum — the common hedge plant whose crushed leaves share the molecule's sharp green-aldehydic smell. Ligustrum itself comes from the Latin ligare, 'to bind,' because privet branches were traditionally used to make twine and woven fences. A molecule named after binding hedges, used to give perfume its greenest, most outdoor character.
Extraction & Chemistry
Extraction method: Fully synthetic. Produced by a one-step Diels-Alder cycloaddition: 2-methyl-1,3-pentadiene (the diene) reacts with acrolein (the dienophile) at 45-75°C under 0.1-0.5 MPa pressure, then aged at 70-100°C for 2-6 hours. Vacuum distillation yields the product as a roughly equal mixture of cis- and trans-isomers (both olfactively active). Assay: 97-100% sum of isomers. No natural source exists, though the non-proprietary name Ligustral references the privet genus (Ligustrum), whose crushed leaves share the molecule's green-aldehydic character.
Restricted by IFRA (49th Amendment, maintained in 51st). Critical effect: dermal sensitisation (QRA2). Maximum in fine fragrance (Category 4): 2.5%. Category 3 (face/body): 2.7%. Category 9 (rinse-off): 4.9%. Limits apply to the sum of all dimethylcyclohex-3-ene-1-carbaldehyde isomers.
Colorless to pale yellow liquid with green, floral, aldehydic odor
Boiling Point
196°C @ 760 mmHg
Flash Point
151°F (66°C) TCC
Specific Gravity
0.932-0.940 @ 25°C
Refractive Index
1.469-1.475 @ 20°C
In Perfumery
Top-note signature and green-accord anchor. Dimethylcyclohex-3-ene-1-carbaldehyde delivers the single most powerful green note available in modern aroma chemistry. At 0.1-0.3%, it lifts floral compositions without imposing an identifiable green character — it simply makes the florals smell more alive, more outdoor, less synthetic. At 0.5-1%, it defines the green quality of a composition: ivy, hedge, leaf stem. Structural in green chypres, modern fougères, and any composition that needs a naturalistic green opening. In jasmine and muguet accords, small doses (0.05-0.2%) add the aldehydic leafy edge that separates a convincing floral from a flat one. In citrus colognes, it reinforces the peel-rind bitterness without adding sweetness. The molecule blends naturally with cis-3-hexenol, galbanum, violet leaf absolute, and hydroxycitronellal. IFRA-restricted to 2.5% in fine fragrance (Category 4), though typical usage in fine perfumery runs 0.1-0.65%. Stability is good in most bases but poor in bleach and strong acid systems.
