In short
Aldehyde C-8, octanal, is an aliphatic aldehyde with a sharp, fatty-citrus smell reminiscent of orange and lemon peel. It is used in traces to give citrus accords realism.
What Aldehyde C-8 (Octanal) smells like
Octanal (aldehyde C-8) is a fatty, citrus-orange aldehyde with a green, peely edge. Suppliers list fatty and orange, and aldehydic, waxy, citrus orange with a green peel nuance. Neat it is harsh and pungent; diluted to around 1% or less it gives a citrus-peel character, which one supplier describes as lemon-lime. It oxidises readily in air, turning sour and rancid.
- Leading note
- Fatty orange
- Clear facets
- Green peel
- Supporting facets
- Waxy
- Faint facets
- Lemon-lime
- Character
- Sharp, fatty, pungent, fresh
What makes Aldehyde C-8 (Octanal) distinctive
It is the sharp, green end of the citrus aldehydes: more pungent and peel-green than decanal, which is rounder orange peel, and fattier and more citrus than heptanal.
Concentration and dilution
Harsh and pungent neat; on dilution to around 1% or less it becomes citrus peel.
How Aldehyde C-8 (Octanal) is used
Used in traces as a top-note modifier in citrus accords, to make orange and lemon notes read as fresh peel.
Typical role: modifier (used in small amounts to change the character of a blend).
How Aldehyde C-8 (Octanal) differs from similar materials
- Aldehyde C-10 (Decanal)
- Decanal is the fuller, rounder orange peel; octanal is sharper, more pungent and greener, closer to lemon-lime in dilution.
- Aldehyde C-7 (Heptanal)
- Heptanal is greener and herbal, with a boozy nuance; octanal is fatty orange and citrus peel.
- Aldehyde C-9 (Nonanal)
- Nonanal turns rosy and waxy; octanal stays citrus — sharper, fattier orange peel.
- Octyl Acetate
- Octyl acetate is the fruity ester of the same chain, orange with jasmine and neroli; octanal is the sharp, fatty aldehyde.
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 strong and prone to oxidation; work from dilutions and store cold.
Identity and classification
- Type
- Aroma chemical
- Origin
- Occurs in nature
- Odour family
- Aldehydic / Citrus
- Note position
- Top note
- Physical form at room temperature
- Liquid
- Also known as
- Octanal, Caprylic aldehyde
- CAS number
- 124-13-0
- Molecular formula
- C8H16O
- Molecular weight
- 128.21 g/mol
- IUPAC name
- octanal
The CAS number, formula and molecular weight are taken from PubChem compound 454, 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 (1,971 reports): H315 causes skin irritation (97.4% of reports); H319 causes serious eye irritation (97.3% of reports); H226 flammable liquid and vapor (93.3% of reports); H411 toxic to aquatic life with long lasting effects (77.1% of reports); H412 harmful to aquatic life with long lasting effects (19.8% of reports). 1 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
-
Aldehyde C-9 (Nonanal)
Aroma chemical · Aldehydic / Floral — aldehydic, waxy, rosy, citrus
-
Lemon Oil (Cold-Pressed)
Essential oil · Citrus / Aldehydic — citrus, sharp, zesty, juicy
Aldehyde C-8 (Octanal) is also suggested as a partner on the pages for Aldehyde C-7 (Heptanal), cis-4-Decenal and Octyl Acetate.
Used in formulas and accords
Used in 8 published formulas
Aldehyde C-8 (Octanal) is an ingredient in 5 perfume formulas and 3 accords in the Formula & Accord Library.
Community formulas
RUŌOD House Originals
Original compositions by RUŌOD House.
Further reading
Questions about Aldehyde C-8 (Octanal)
Is Aldehyde C-8 (Octanal) natural or synthetic?
The molecule occurs in nature. Commercial Aldehyde C-8 (Octanal) 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-8 (Octanal)?
124-13-0. It was checked against PubChem on 19 October 2026.
Which published formulas use Aldehyde C-8 (Octanal)?
Aldehyde C-8 (Octanal) is used in 8 published formulas in the RUŌOD Lab Formula & Accord Library, including Champagne Static, Cherry Accord and Cola Amber. Each is listed with a link under "Used in formulas and accords" on this page.
Sources
- PubChem — compound 454, 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 — octanal — odour database.
- ChemicalBook — octanal (CAS 124-13-0) — odour database.
- Scent.vn — Aldehyde C-8 Octanal — distributor's description.
- Olfactory profile: the RUŌOD Lab team's synthesis of the published descriptions above, reviewed 20 October 2026. Evidence: several independent published descriptions, which agree. Classification and the short description: revision 1. Descriptions of odour are judgement, not measurement.