trans-2-Hexenal

What trans-2-Hexenal smells like

Trans-2-hexenal, leaf aldehyde, is a sharp, intensely green and leafy material with a distinct green-apple side. Neat it is pungent, with an acrid, vegetable-green sharpness; diluted it becomes pleasantly green and apple-like. Descriptions add herbal and watermelon nuances, and at higher concentration a fatty edge. It is the stable aldehyde that forms when cut grass releases cis-3-hexenal, and its odour threshold is far lower than that of leaf alcohol, which makes it the more penetrating of the two.

Leading note

Sharp leafy green

Clear facets

Green apple

Supporting facets

Herbal

Faint facets

Fatty, watermelon

Character

Sharp, pungent, green, crisp

• green
• leafy
• apple
• sharp
• fresh

What makes trans-2-Hexenal distinctive

Its bite. Among the leaf greens it is the aldehyde — sharper and more pungent than cis-3-hexenol, and with an unripe-apple crispness the alcohol does not have.

Concentration and dilution

Pungent and acrid neat, with a sharp vegetable greenness; on dilution it turns pleasantly green and apple-like.

How trans-2-Hexenal is used

Used in traces for a crisp green-apple and leafy top note in fruity, green and fresh compositions, and in fruit flavours. It fades quickly from the blotter.

Typical role: modifier (used in small amounts to change the character of a blend); lift (adds diffusion and radiance, especially at the top).

How trans-2-Hexenal differs from similar materials

cis-3-Hexenol

Leaf alcohol is the softer, more literal cut grass; trans-2-hexenal is sharper and more pungent, with a green-apple crispness.

trans-2-Hexenol

The alcohol is sweeter, fruitier and wine-like; the aldehyde is the sharp, pungent leaf note.

Leaf Acetal

Leaf acetal, built on leaf alcohol, is described as powerful, green and herbaceous rather than sharp and aldehydic.

Each difference compares the published descriptions of the two materials. Smell varies with grade, supplier and dilution; compare them side by side on blotters before substituting one for another.

Formulation considerations

Very volatile and reactive. Use from dilution and expect it to change in alkaline or oxidising bases.

Identity and classification

Type

Aroma chemical

Origin

Occurs in nature

Odour family

Green / Fruity

Note position

Top note

Physical form at room temperature

Liquid

Also known as

Leaf aldehyde, (E)-Hex-2-enal

CAS number

6728-26-3

Molecular formula

C6H10O

Molecular weight

98.14 g/mol

IUPAC name

(E)-hex-2-enal

The CAS number, formula and molecular weight are taken from PubChem compound 5281168, whose own record lists this CAS number; checked 19 October 2026.

Safety and compliance

The IFRA Standards Library lists a Standard covering trans-2-Hexenal:

• "2-Hexenal" — Restriction, 51st Amendment, published 2023-06

Limits differ by product category and are set out in the Standard itself; this page does not reproduce them. The list above reflects the library as read on 19 October 2026.

Hazard classification of the neat substance, as PubChem summarises it, read 26 October 2026. Companies notifying the ECHA C&L Inventory classify it (1,801 reports): H302 harmful if swallowed (99.7% of reports); H317 may cause an allergic skin reaction (99.4% of reports); H226 flammable liquid and vapor (96.6% of reports); H311 toxic in contact with skin (96.4% of reports); H411 toxic to aquatic life with long lasting effects (94.8% of reports); H319 causes serious eye irritation (78.7% of reports). A skin sensitiser classification concerns handling the neat material and the dose in a finished product; the IFRA Standards, where they apply, set the limits. Unless it is harmonised, this is the notifiers' own classification, not a binding one.

This page is general information, not a safety assessment or a specification. Confirm identity, composition, IFRA status and allergen content from your supplier's documents for the lot you hold.

Materials it works with

• cis-3-Hexenol

  Aroma chemical · Green / Fruity — green, cut grass, leafy, fresh

• cis-3-Hexenyl Acetate

  Aroma chemical · Green / Fruity — green, fruity, unripe banana, fresh

• Hexyl Acetate

  Aroma chemical · Fruity / Green — pear, apple, fruity, green

• Galbanum Oil

  Essential oil · Green / Resinous — green, sharp, bitter, resinous

trans-2-Hexenal is also suggested as a partner on the pages for 1-Hexanol, Leaf Acetal and trans-2-Hexenol.

Used in formulas and accords

Used in 1 published formula

trans-2-Hexenal is an ingredient in 1 accord in the Formula & Accord Library.

• Brined Olive Accord

  Community Formula · Accord · listed as “Trans - 2 - Hexanal 1%”, at 1%

Further reading

• Green Notes in Perfumery: Leaf, Galbanum and Violet Leaf

  The green palette — cis-3-hexenol, galbanum, violet leaf, styrallyl acetate — what green notes do, dosage, restrictions and pairings.

• Fruity Notes in Perfumery: Esters, Lactones and Ketones

  How fruit is built in perfumery from esters, lactones, ketones and sulfur materials, why 'C-14' is a lactone, dosage, stability and restrictions.

Questions about trans-2-Hexenal

Sources

• PubChem — compound 5281168, checked 19 October 2026.
• PubChem — GHS classification (the ECHA C&L Inventory notifications and any harmonised EU entry), read 26 October 2026.
• IFRA — Standards Library, read 19 October 2026.
• Wikipedia — trans-2-Hexenal — published perfumery reference.
• FooDB — (E)-2-hexenal — odour database.
• ChemicalBook — trans-2-hexenal (CAS 6728-26-3) — odour database.
• Parchem — (E)-2-hexen-1-al — distributor's description.
• Olfactory profile: the RUŌOD Lab team's synthesis of the published descriptions above, reviewed 24 October 2026. Evidence: several independent published descriptions, which agree. Classification and the short description: revision 1. Descriptions of odour are judgement, not measurement.