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Chemical Sampling Information (CSI)
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General Description

Synonyms: Isobutaldehyde; Isobutanal; Isobutyl aldehyde; Isobutyric Aldehyde; Isopropylformaldehyde; Methyl Propanal; 2-Methyl-1-propanol; 2-Methylpropanal; 2-Methylpropionaldehyde; Valine Aldehyde

OSHA IMIS Code Number: R237

Chemical Abstracts Service (CAS) Registry Number: 78-84-2

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: NQ4025000

Department of Transportation Regulation Number (49 CFR 172.101) and Guide: 2045 130

Chemical Description and Physical Properties:

colorless liquid with pungent odor
molecular weight: 72.1
vapor pressure: 15.3 kPa @ 20°C
molecular formula: C4H8O
boiling point: 63-64°C
melting point: -65°C
flash point: -40°C closed cup; -23.9°C open cup

Incompatibilities: very dangerous fire hazard when exposed to heat, flame, or oxidizers - reacts with oxidants, strong reductants and strong bases

Health Factors

Potential Symptoms: Irritation of eyes, skin, nose, throat; cough, sore throat, shortness of breath, labored breathing, pulmonary edema (may be delayed); eye and skin pain, redness, burns; skin blisters; contact dermatitis; loss of vision; INGES. ACUTE: Burning sensation, abdominal cramps; shock or collapse

Health Effects: Irritation-Eyes, Nose, Throat, Skin---Marked (HE14); Pulmonary edema (HE4)

Affected Organs: Eyes, skin, respiratory system


  1. OSHA does not have a PEL for isobutyraldehyde.
  2. Vapor/air mixtures of isobutryaldehyde may be explosive.
  3. Isobutyraldehyde occurs naturally in some foods, such as white bread, beer, and chocolate, and it is listed by the FDA as a synthetic flavoring substance that is permitted for direct addition to food for human consumption (21 CFR 172.515).
  4. Two-year carcinogenicity studies were negative for cancer, but non-neoplastic nasal lesions were caused at inhaled isobutyraldehyde concentrations of 1000 and 2000 ppm in rats and mice. Higher concentrations (4000 and 8000 ppm) were lethal to some rats and mice in 13-week inhalation studies.
  5. Several cytochrome P-450 isozymes have been identified in rabbit liver, which can metabolize isobutyraldehyde to propylene.

Literature Basis:

  • International Chemical Safety Cards (WHO/IPCS/ILO): Isobutyraldehyde.
  • Abdo, K.M., Haseman, J.K. and Nyska, A.: Isobutyraldehyde administered by inhalation (whole body exposure) for up to thirteen weeks or two years was a respiratory tract toxicant but was not carcinogenic in F344/N rats and B6C3F1 mice. Toxicol. Sci. 42(2): 136-151, 1998.
  • Counet, C., Callemien, D., Ouwerx, C. and Collin, S.: Use of gas chromatography-olfactometry to identify key odorant compounds in dark chocolate. Comparison of samples before and after conching. J. Agric. Food Chem. 50(8): 2385-2391, 2002.
  • Pohanish, R.P. (editor): Isobutyraldehyde. In, Sittig’s Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 2. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 1329-1330.
  • Roberts, E.S., Vaz, A.D.N. and Coon, M.J.: Catalysis by cytochrome P-450 of an oxidative reaction in xenobiotic aldehyde metabolism: deformylation with olefin formation. Proc. Natl. Acad. Sci. U.S.A. 88(20): 8963-8966, 1991.

Date Last Revised: 02/05/2007

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: Coated XAD-2 Tube (150/75 mg sections, 20/60 mesh); coating is 10% (w/w) 2-(Hydroxymethyl)piperidine
    analytical solvent: Toluene
    maximum volume: 5 Liters
    maximum flow rate: 0.05 L/min
    current analytical method: Gas Chromatography; GC/NPD with GC/MS identification
    method reference: OSHA Modified NIOSH Analytical Method (NIOSH 2539 [255 KB PDF, 10 pages])
    method classification: Partially Validated
    note: OSHA modification is use of GC/NPD in place of GC/FID. This is a screening method and is not quantitative.

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