Ingredient Dictionary

ISOBUTYRIC ACID

Isobutyric acid is a branched fatty acid comprising propanoic acid carrying a methyl branch at C-2.

Definition

Isobutyric acid is a branched fatty acid comprising propanoic acid carrying a methyl branch at C-2. It has a role as a volatile oil component, a plant metabolite and a Daphnia magna metabolite. It is a fatty acid 4:0, a branched-chain saturated fatty acid and a methyl-branched fatty acid. It is a conjugate acid of an isobutyrate.

Source: PubChem

US FDA substance register · UNII 8LL210O1U0 · registered name Isobutyric acid · single chemical substance

Source: US FDA Unique Ingredient Identifier (UNII)

Cosmetic roles

Keeps pH steadyBUFFERING

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

ISOBUTYRIC ACIDINCI아이소부티릭애씨드Korean label name (MFDS standard)Propanoic acid, 2-methyl-Synonym

CAS No.chemical registry number: 79-31-2
EC No.EU chemical inventory number: 201-195-7
DTXSIDUS EPA chemical ID: DTXSID4021636
DTXCIDUS EPA compound ID: DTXCID601636

IUPAC: 2-Methylpropanoic acid
Molecular formula: C4H8O2
Molecular weight: 88.106 g/mol

Measured properties

Appearance: Isobutyric acid appears as a colorless liquid with a light odor of rancid butter. Corrosive to metals and tissue. · Liquid
Odour: Pungent odor like that of butyric acid, but not as unpleasant · SHARP, BUTTER-FAT-LIKE ODOR
Boiling point: 309 °F at 760 mmHg (USCG, 1999) · 154.4 °C
Melting point: -51 °F (USCG, 1999) · -46 °C
Solubility: 167000 mg/L (at 20 °C) · Slightly soluble in carbon tetrachloride
Density: 0.949 at 68 °F (USCG, 1999) - Less dense than water, will float · 0.950 at 20 °C/4 °C
Stability: Stable during transport.
Viscosity: 1.126 mPa.s · (1.126 mPa.s)
Dissociation constant: 4.84 (at 20 °C) · pKa = 4.84
Colour: colourless
Odour threshold: 8.1 ppm
pH: 2.9
Melting/freezing point: -47 ℃
Initial boiling point and range: 152~155 ℃
Flash point: 56 ℃
Upper/lower flammability or explosive limits: 9 / 2
Vapour pressure: 0.13 ㎪ (at 14.7℃)
Water solubility: 167000 ㎎/ℓ
Vapour density: 3
Relative density: 0.95 (at 20℃)
n-Octanol/water partition coefficient (Kow): 0.94
Auto-ignition temperature: 481 ℃
Molecular weight: 88.11

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 9 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.

Fragrance2
Intermediate2
Flavouring and nutrient2
No specific technical function1
Solvent1
pH regulating agent1

Source: US EPA CompTox dashboard

Irritation and sensitisation studies

5 skin studies and 2 eye studies are on record.

Classed as highly irritating2

The study conclusions largely agree (100%). These tests are on the raw material itself; irritation at the amount in a finished product is a different question.

See all 7 studies

Skin corrosion/irritation - Category 1
Skin Irritation · Screening
Corrosive
skin irritation: in vivo · Screening · OECD Guideline 404 (Acute Dermal Irritation / Corrosion) 1981 according to
Category 8.2C (Category 1C)
Skin Irritation · Read Across
Classification not possible
Skin Sensitization · Screening
Category 1
Skin Irritation · Screening
Category 1
Eye Irritation · Screening
Category 8.3A (Category 1)
Eye Irritation · Read Across