alpha-Terpinene

What alpha-Terpinene smells like

JECFA, as published by PubChem, describes alpha-terpinene as a colourless oily liquid with a refreshing, lemony-citrus aroma. PubChem links it to several natural-product databases. Sigma-Aldrich's food-grade listing gives lemon, medicinal, citrus and woody as its organoleptic profile.

Leading note

Lemony

Clear facets

Citrus

Character

Refreshing

• lemon
• citrus
• fresh

What makes alpha-Terpinene distinctive

A terpene that reads as lemon rather than as pine or herb.

How alpha-Terpinene is used

Used in citrus and herbal reconstructions and fresh top notes.

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

How alpha-Terpinene differs from similar materials

gamma-Terpinene

gamma-Terpinene is the herbal, citrus-terpenic isomer; alpha-terpinene is described as refreshing and lemony-citrus.

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

Like other terpenes, it oxidises in air.

Identity and classification

Type

Aroma chemical

Origin

Occurs in nature

Odour family

Citrus / Aromatic

Note position

Top note

Physical form at room temperature

Liquid

Also known as

α-Terpinene

CAS number

99-86-5

Molecular formula

C10H16

Molecular weight

136.23 g/mol

IUPAC name

1-methyl-4-propan-2-ylcyclohexa-1,3-diene

The CAS number, formula and molecular weight are taken from PubChem compound 7462, whose own record lists this CAS number; checked 24 October 2026.

Safety and compliance

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; H302 harmful if swallowed; H304 may be fatal if swallowed and enters airways; H317 may cause an allergic skin reaction; H411 toxic to aquatic life with long lasting effects. Companies notifying the ECHA C&L Inventory classify it (2,054 reports): H226 flammable liquid and vapor (100% of reports); H411 toxic to aquatic life with long lasting effects (98.9% of reports); H304 may be fatal if swallowed and enters airways (94.8% of reports); H319 causes serious eye irritation (16.7% of reports); H317 may cause an allergic skin reaction (16.1% 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

• gamma-Terpinene

  Aroma chemical · Citrus / Aromatic — citrus, herbal, oily, lime

• d-Limonene

  Aroma chemical · Citrus / Fruity — citrus, orange, fresh, light

• Terpinolene

  Aroma chemical · Aromatic / Woody — piney, herbal, citrus, woody

Used in formulas and accords

Used in 1 published formula

alpha-Terpinene is an ingredient in 1 accord in the Formula & Accord Library.

• Pumpkin Accord

  Community Formula · Accord · listed as “Alpha Terpinene”

Further reading

• Citrus Oils in Perfumery: Bergamot, Lemon, Orange and Their Limits

  The main citrus oils, phototoxicity and FCF bergamot, why citrus fades and how to extend it, oxidation, allergens, and grades from expressed to terpeneless.

Questions about alpha-Terpinene

Sources

• PubChem — compound 7462, checked 24 October 2026.
• PubChem — GHS classification (the ECHA C&L Inventory notifications and any harmonised EU entry), read 26 October 2026.
• PubChem — Alpha-Terpinene (CID 7462): JECFA organoleptic description — odour database.
• Sigma-Aldrich — alpha-terpinene (W355801) — manufacturer's description.
• Olfactory profile: the RUŌOD Lab team's synthesis of the published descriptions above, reviewed 26 October 2026. Evidence: more than one published description. Classification and the short description: revision 1. Descriptions of odour are judgement, not measurement.