cis-4-Decenal

In short

cis-4-Decenal is an unsaturated aldehyde with a powerful fatty-orange odour. It is used in very small amounts to make orange and other citrus accords smell juicier and more like fresh peel.

What cis-4-Decenal smells like

cis-4-Decenal is a juicy citrus aldehyde with an orange and mandarin character. The Good Scents Company lists citrus, aldehydic, orange, watery and cardamom for the cis isomer, and a flavour profile of zesty citrus peel, herbal, fresh, fatty, fruity and floral; FlavorDB adds tangerine and mandarin. A patent describes using 4-decenal to enhance mandarin and tangerine character, noting its pulpy, juicy quality, and Arcadi Boix Camps described it as an extremely agreeable citric-aldehydic, orange-flower odour while warning of its strength.

Leading note: Juicy orange
Clear facets: Mandarin, tangerine
Supporting facets: Fatty, watery
Faint facets: Cardamom
Character: Juicy, fatty, fresh, intense

What makes cis-4-Decenal distinctive

Pulp rather than peel. Decanal smells of waxy orange zest; cis-4-decenal is the juicy, pulpy side of orange and mandarin.

Concentration and dilution

Intensely fatty and harsh when concentrated; diluted, it reads as juicy, fruity citrus.

Where the descriptions disagree: Most supplier descriptions are for the mixed or trans isomers; the cis isomer's own descriptors are sparser and less mandarin-heavy.

How cis-4-Decenal is used

Used in traces to give orange, mandarin and tangerine accords a juicy, pulpy realism, in fragrance and flavour.

Typical role: modifier (used in small amounts to change the character of a blend).

How cis-4-Decenal differs from similar materials

Aldehyde C-10 (Decanal): Decanal is waxy orange zest; cis-4-decenal is juicier and more mandarin-like, the pulp rather than the peel.
trans-2-Decenal: trans-2-Decenal pairs its orange with coriander leaf and a fatty, chicken-fat note neat; cis-4-decenal is cleaner, juicier mandarin.

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

Extremely potent; dose by the drop from a 0.1% dilution. Prone to oxidation, so keep it cold and away from air.

Identity and classification

Type: Aroma chemical
Origin: Occurs in nature
Odour family: Citrus / Aldehydic
Note position: Top note
Physical form at room temperature: Liquid
Also known as: (Z)-Dec-4-enal
CAS number: 21662-09-9
Molecular formula: C10H18O
Molecular weight: 154.25 g/mol
IUPAC name: (Z)-dec-4-enal

The CAS number, formula and molecular weight are taken from PubChem compound 5362620, whose own record lists this CAS number; checked 19 October 2026.

Safety and compliance

Hazard classification of the neat substance, as PubChem summarises it, read 26 October 2026. Companies notifying the ECHA C&L Inventory classify it (370 reports): H315 causes skin irritation (11.9% of reports); H319 causes serious eye irritation (11.9% of reports); H335 may cause respiratory irritation (10.5% of reports). 311 of the reports find it does not meet the hazard criteria. 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

Sweet Orange Oil
Essential oil · Citrus / Fruity — citrus, sweet, juicy, orange peel
Aldehyde C-10 (Decanal)
Aroma chemical · Aldehydic / Citrus — aldehydic, waxy, orange peel, fatty
Aldehyde C-8 (Octanal)
Aroma chemical · Aldehydic / Citrus — aldehydic, fatty, citrus, orange
Grapefruit Oil (Expressed)
Essential oil · Citrus / Fruity — citrus, bitter, juicy, sparkling

Used in formulas and accords

Used in 2 published formulas

cis-4-Decenal is an ingredient in 2 perfume formulas in the Formula & Accord Library.

RUŌOD House Originals

Original compositions by RUŌOD House.

Fig Jam Brioche
RUŌOD House Original · listed as “cis-4-Decenal 1% DPG”, at 1% in DPG
Orange Soda Sunset
RUŌOD House Original · listed as “cis-4-Decenal 1% DPG”, at 1% in DPG

Questions about cis-4-Decenal

Is cis-4-Decenal natural or synthetic?

The molecule occurs in nature. Commercial cis-4-Decenal may be made by synthesis or obtained from natural sources, so check the supplier's specification if the distinction matters to you.

What is the CAS number of cis-4-Decenal?

21662-09-9. It was checked against PubChem on 19 October 2026.

Which published formulas use cis-4-Decenal?

cis-4-Decenal is used in 2 published formulas in the RUŌOD Lab Formula & Accord Library: Fig Jam Brioche and Orange Soda Sunset. Each is listed with a link under "Used in formulas and accords" on this page.

Sources

PubChem — compound 5362620, checked 19 October 2026.
PubChem — GHS classification (the ECHA C&L Inventory notifications and any harmonised EU entry), read 26 October 2026.
The Good Scents Company — (Z)-4-decenal — odour database.
FlavorDB — cis-4-decenal — odour database.
ChemicalBook — 4-decenal (CAS 65405-70-1) — odour database.
Olfactory profile: the RUŌOD Lab team's synthesis of the published descriptions above, reviewed 20 October 2026. Evidence: more than one published description. Classification and the short description: revision 1. Descriptions of odour are judgement, not measurement.