In short
This record is limonene when a formula does not say which stereoisomer it means. PubChem records CAS 138-86-3 for limonene with its stereochemistry undefined.
What Limonene (isomer not specified) smells like
PubChem's safety records for limonene with undefined stereochemistry (CID 22311) describe a colourless liquid with an odour of lemon, or a citrus-like odour. The individual stereoisomers have their own descriptions; this record makes no claim about which one a formula used.
- Leading note
- Citrus
- Supporting facets
- Lemon
- Character
- Fresh
What makes Limonene (isomer not specified) distinctive
Limonene with no isomer stated: the record for formulas that do not say whether they used d-, l- or a racemic limonene.
How Limonene (isomer not specified) is used
Used for a fresh citrus lift and in citrus reconstitutions; the specific isomer used should be checked against the supplier's specification.
Typical role: lift (adds diffusion and radiance, especially at the top); blender (smooths the joins between other materials).
How Limonene (isomer not specified) differs from similar materials
- d-Limonene
- d-Limonene is the defined isomer that makes up most citrus oils, a thin orange-peel note; this record is for limonene whose isomer a formula does not state, so it may be d-limonene or another form.
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
Limonene has two mirror-image forms, d-limonene and l-limonene, which smell different and are separate materials. Where a formula prints only "Limonene", the isomer is not known, so its lines are matched here rather than to either form. The same CAS number is also used for dipentene, a technical grade of mixed terpenes, which is not what this record describes.
Identity and classification
- Type
- Aroma chemical
- Origin
- Occurs in nature
- Odour family
- Citrus
- Note position
- Top note
- Physical form at room temperature
- Liquid
- CAS number
- 138-86-3
- Molecular formula
- C10H16
- Molecular weight
- 136.23 g/mol
- IUPAC name
- 1-methyl-4-prop-1-en-2-ylcyclohexene
The CAS number, formula and molecular weight are taken from PubChem compound 22311, whose own record lists this CAS number; checked 25 October 2026.
Safety and compliance
The IFRA Standards Library lists a Standard covering Limonene (isomer not specified):
- "Limonene" — Specification, 29th Amendment, published 1995-01
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. It has a harmonised EU classification (Regulation (EC) No 1272/2008, Annex VI): H226 flammable liquid and vapor; H315 causes skin irritation; H317 may cause an allergic skin reaction; H400 very toxic to aquatic life; H410 very toxic to aquatic life with long lasting effects. Companies notifying the ECHA C&L Inventory classify it (3,461 reports): H400 very toxic to aquatic life (98.6% of reports); H304 may be fatal if swallowed and enters airways (49.2% of reports); H319 causes serious eye irritation (14.9% of reports). 1 of the reports find it does not meet the hazard criteria. 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
-
d-Limonene
Aroma chemical · Citrus / Fruity — citrus, orange, fresh, light
-
Sweet Orange Oil
Essential oil · Citrus / Fruity — citrus, sweet, juicy, orange peel
-
Lemon Oil (Cold-Pressed)
Essential oil · Citrus / Aldehydic — citrus, sharp, zesty, juicy
Used in formulas and accords
Used in 17 published formulas
Limonene (isomer not specified) is an ingredient in 13 accords and 4 bases in the Formula & Accord Library.
Further reading
Questions about Limonene (isomer not specified)
Is Limonene (isomer not specified) natural or synthetic?
The molecule occurs in nature. Commercial Limonene (isomer not specified) 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 Limonene (isomer not specified)?
138-86-3. It was checked against PubChem on 25 October 2026.
Which published formulas use Limonene (isomer not specified)?
Limonene (isomer not specified) is used in 17 published formulas in the RUŌOD Lab Formula & Accord Library, including Açaí Accord, Blackberry Accord and Blue Accord. Each is listed with a link under "Used in formulas and accords" on this page.
Is Limonene (isomer not specified) covered by an IFRA Standard?
Yes. The IFRA Standards Library lists a Standard covering it: "Limonene" — Specification, 29th Amendment. The limits depend on the product category; read the Standard itself before formulating.
Sources
- PubChem — compound 22311, checked 25 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.
- PubChem — limonene, stereochemistry undefined (CAMEO, OSHA and Haz-Map descriptions) (CID 22311) — odour database.
- Olfactory profile: the RUŌOD Lab team's synthesis of the published descriptions above, reviewed 26 October 2026. Evidence: few published descriptions; treat the detail with caution. Classification and the short description: revision 1. Descriptions of odour are judgement, not measurement.