Ingredient Dictionary

4-METHYLPENT-3-EN-2-ONE

4-Methyl-3-penten-2-one, 9CI is an olefinic compound.

Definition

4-Methyl-3-penten-2-one, 9CI is an olefinic compound. It is functionally related to an acrylic acid.

Source: PubChem

US FDA substance register · UNII 77LAC84669 · registered name Mesityl oxide · single chemical substance

Source: US FDA Unique Ingredient Identifier (UNII)

Cosmetic roles

Gives the product a scentPERFUMING

Safety & regulatory references

Not classified under Korea’s toxic-substance GHS list · existing chemical substance

Source: Korea toxic substances GHS register (NIER)

More data — names, identifiers, properties, test records, literature

Names & identifiers

4-METHYLPENT-3-EN-2-ONEINCI3-Penten-2-one, 4-methyl-Synonym

CAS No.chemical registry number: 141-79-7
EC No.EU chemical inventory number: 205-502-5
DTXSIDUS EPA chemical ID: DTXSID1029170
DTXCIDUS EPA compound ID: DTXCID209170

IUPAC: 4-Methylpent-3-en-2-one
Molecular formula: C6H10O
Molecular weight: 98.145 g/mol

Measured properties

Appearance: Mesityl oxide appears as a colorless, oily liquid with a pungent honey-like odor. Flash point 87 °F. Less dense than water and slightly soluble in water. Vapors heavier than air. Used in paint removers, as a solvent for plastics, and as an insect repellent. · Oily, colorless to light-yellow liquid with a peppermint- or honey-like odor, [NIOSH]
Odour: ... spearmint ... · COMMERCIAL GRADE EXHIBITS AN UNPLEASANT ODOR
Boiling point: 266 °F at 760 mmHg (USCG, 1999) · 130 °C at 760 mm Hg
Melting point: -51 °F (USCG, 1999) · -59 °C
Solubility: 3 % (NIOSH, 2024) · Sol in about 30 parts water, miscible with most org liq
Density: 0.853 at 68 °F (USCG, 1999) - Less dense than water, will float · 0.8592 at 15 °C/4 °C
Melting/freezing point: -59 ℃
Initial boiling point and range: 130 ℃
Flash point: 25 ℃(101.3 kPa EU Method A.9, GLP)
Upper/lower flammability or explosive limits: 7.2 / 1.4 %
Vapour pressure: 1.2 ㎪ (20℃)
Water solubility: 26.98 (20℃, pH=3.7 (OECD TG , GLP), g/L)
Vapour density: 3.4 (air=1)
Relative density: 0.8592 (15℃/4℃)
n-Octanol/water partition coefficient (Kow): 1.37
Auto-ignition temperature: 335 ℃ (1013 hPa, (EU Method A.15))
Viscosity: 0.717 (20.15 °C, (OECD TG 114, GLP))
Molecular weight: 98.14

Values measured on the substance itself. The KOSHA data are a reference for writing and reviewing safety data sheets, not a specification for a commercial raw material.

Source: PubChem · KOSHA safety data sheets (Korea)

What products actually use it for

What the 8 products reported to the US EPA with this ingredient use it for. Products outside cosmetics are included, so the top few rows are its main uses.

Solvent4
Fragrance2
Flavouring and nutrient2

Source: US EPA CompTox dashboard

Irritation and sensitisation studies

5 skin studies and 4 eye studies are on record.

Classed as highly irritating1Classed as moderate1Classed as low1

The studies disagree (the most common conclusion covers 33%), so they do not establish that this ingredient is irritating. These tests are on the raw material itself; irritation at the amount in a finished product is a different question.

See all 9 studies

Severe Irritation
skin irritation: in vivo · Screening · OECD Guideline 404 (Acute Dermal Irritation / Corrosion) according to EPA OPPTS 870.2500 (Acute Dermal Irritation) according to EU Method B.4 (Acute Toxicity: Dermal Irritation / Corrosion) according to
Category 6.3B (Category 3)
Skin Irritation · Read Across
Category 2
Skin Irritation · Screening
Classification not possible
Skin Sensitization · Screening
Not likely to be sensitizing
skin sensitisation: in vivo (non-LLNA) · Screening · according to OECD Guideline 406 (Skin Sensitisation) according to EU Method B.6 (Skin Sensitisation)
Serious eye damage/eye irritation - Category 2
Eye Irritation · Screening
Category 2A
Eye Irritation · Screening
Severe Irritation
eye irritation: in vitro / ex vivo · Screening · other guideline: OECD 437 "Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants (adopted 7 September 2009) according to
Category 8.3A (Category 1)
Eye Irritation · Read Across