Aldehyde C-9 (Nonanal)

In short

Aldehyde C-9, nonanal, is an aliphatic aldehyde with a waxy, rosy-citrus odour. It occurs in rose and citrus oils and adds a fresh, slightly fatty sparkle in traces.

What Aldehyde C-9 (Nonanal) smells like

Nonanal (aldehyde C-9) is a waxy, aldehydic material whose citrus side turns towards rose. Firmenich describes a classical aldehyde note — waxy, citrus, floral and green; Givaudan aldehydic, fatty, rosy and citrus; Bedoukian strong, floral and mostly orange. Parchem adds a slightly green lemon-peel nuance and a cucumber-like fattiness. It occurs in rose and citrus oils and is used to improve rose-like odours.

Leading note: Waxy aldehydic
Clear facets: Rose, orange and citrus peel
Supporting facets: Fatty
Faint facets: Green, cucumber
Character: Waxy, fatty, fresh, soft

What makes Aldehyde C-9 (Nonanal) distinctive

The rose. Of the straight-chain aldehydes it is the one whose waxiness reads floral and rosy as well as citrus — the reason it is used in rose compositions, not only in citrus ones.

How Aldehyde C-9 (Nonanal) is used

Used at low levels for aldehydic lift in floral and citrus compositions, and particularly to make rose notes more natural.

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

How Aldehyde C-9 (Nonanal) differs from similar materials

Aldehyde C-8 (Octanal): Octanal is sharper and more pungent, fatty orange peel; nonanal is waxier and rosier.
Aldehyde C-10 (Decanal): Decanal is the powerful orange-peel aldehyde; nonanal shares its waxiness but tilts towards rose rather than orange.
Rosalva: Rosalva is an alcohol, dewier and more specifically rose-petal; nonanal is a waxy aldehyde leaning rose and orange.
1-Nonanol: 1-Nonanol (alcohol C-9), its alcohol, is rose-citrus and floral without the aldehydic, waxy edge.

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

Strong; dose from dilution. Oxidises over time.

Identity and classification

Type: Aroma chemical
Origin: Occurs in nature
Odour family: Aldehydic / Floral
Note position: Top note
Physical form at room temperature: Liquid
Also known as: Nonanal, Pelargonaldehyde
CAS number: 124-19-6
Molecular formula: C9H18O
Molecular weight: 142.24 g/mol
IUPAC name: nonanal

The CAS number, formula and molecular weight are taken from PubChem compound 31289, 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 (1,956 reports): H412 harmful to aquatic life with long lasting effects (92.9% of reports); H315 causes skin irritation (19.3% of reports); H319 causes serious eye irritation (18.5% of reports). 83 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

Aldehyde C-10 (Decanal)
Aroma chemical · Aldehydic / Citrus — aldehydic, waxy, orange peel, fatty
Rose Oil (Rosa damascena)
Essential oil · Floral / Fruity — rose, honeyed, spicy, fresh
Phenylethyl Alcohol
Aroma chemical · Floral / Green — rose, honeyed, soft, floral

Aldehyde C-9 (Nonanal) is also suggested as a partner on the pages for 1-Nonanol, Aldehyde C-7 (Heptanal) and Aldehyde C-8 (Octanal).

Used in formulas and accords

Used in 8 published formulas

Aldehyde C-9 (Nonanal) is an ingredient in 4 perfume formulas and 4 accords in the Formula & Accord Library.

Community formulas

Peony Accord
Community Formula · Accord · listed as “Aldehyde C-9”
Tamarind Accord
Community Formula · Accord · listed as “Aldehyde C-9”
Wisteria Accord
Community Formula · Accord · listed as “Aldehyde C9”

RUŌOD House Originals

Original compositions by RUŌOD House.

Champagne Static
RUŌOD House Original · listed as “Aldehyde C-9 (Nonanal) 10% DPG”, at 10% in DPG
Glass Rose Accord
RUŌOD House Accord · listed as “Aldehyde C-9 (Nonanal) 10% DPG”, at 10% in DPG
Maple Fog
RUŌOD House Original · listed as “Aldehyde C-9 (Nonanal) 10% DPG”, at 10% in DPG
Rose Graphite
RUŌOD House Creation · listed as “Aldehyde C-9 (Nonanal) 10% DPG”, at 10% in DPG
Wool Fog
RUŌOD House Original · listed as “Aldehyde C-9 (Nonanal) 10% DPG”, at 10% in DPG

Questions about Aldehyde C-9 (Nonanal)

Is Aldehyde C-9 (Nonanal) natural or synthetic?

The molecule occurs in nature. Commercial Aldehyde C-9 (Nonanal) 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 Aldehyde C-9 (Nonanal)?

124-19-6. It was checked against PubChem on 19 October 2026.

Which published formulas use Aldehyde C-9 (Nonanal)?

Aldehyde C-9 (Nonanal) is used in 8 published formulas in the RUŌOD Lab Formula & Accord Library, including Champagne Static, Glass Rose Accord and Maple Fog. Each is listed with a link under "Used in formulas and accords" on this page.

Sources

PubChem — compound 31289, 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 — nonanal (with Firmenich, Givaudan and Bedoukian descriptions) — odour database.
Parchem — nonanal specification — distributor's description.
ChemicalBook — nonanal (CAS 124-19-6) — odour database.
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.