Triplal

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.

Related Notes

See also: Galbanum, Violet Leaf, Hedione, Basil.

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