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CAS 105-45-3

CAS 105-45-3 matches 0 EU annex records across Annex II–VI of Regulation 1223/2009.

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Chemical identity and properties

PubChem 2D chemical structure for CAS 105-45-3
CAS 105-45-3PubChem CID 7757

Methyl acetoacetate

Methyl acetoacetate appears as a clear colorless liquid. Flash point 158 °F. Denser than water and slightly soluble in water. Vapors heavier than air. — CAMEO Chemicals

IUPAC name
methyl 3-oxobutanoate
Molecular formula
C5H8O3
Molecular weight
116.11 g/mol
Exact mass
116.047344113 Da
XLogP3
0.0
Topological polar surface area
43.4 Ų
Hydrogen-bond donors
0
Hydrogen-bond acceptors
3
Covalent units
1
Defined stereocentres
0

Also known as

MethylacetoacetateMethyl acetylacetateAcetoacetic acid methyl esterMethyl 3-oxobutyrate3-Oxobutanoic acid methyl esterMethyl acetylacetonateButanoic acid, 3-oxo-, methyl esterAcetoacetic methyl ester
16 more reported names
1-Methoxybutane-1,3-dioneAcetoacetic acid, methyl esterMethylester kyseliny acetoctoveCW4I82QAX1RefChem:817587203-299-8Methylacetoacetic acid3-Oxobutyric Acid Methyl Ester3-oxo-butyric acid methyl ester3-oxo-Butanoic acid methyl esterAcetoacetate methyl estermethyl acetoacetate(MAA)METHYL ACETOACETATE [MI]Tox21_200162s3091CAS-105-45-3
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

Evidence from additional scientific databases

EMBL-EBI ChEBI
Exact identifier matchCHEBI:166454

Methylacetoacetic acid

Formula
C5H8O3
Average mass
116.116 g/mol
Monoisotopic mass
116.04734 Da
Formal charge
0
  • oxo carboxylic acid — is a (CHEBI:25754)
  • oxo carboxylic acid — is a (CHEBI:25754)
Additional curated names
methyl 3-oxobutanoate
Cross-references from this source

Mapped by: Exact CAS cross-reference in the ChEBI compound record. Retrieved: 2026-08-31. Open source record

NIH PubChem PUG-View
Exact identifier match7757

Attributed physical-property, hazard, environmental and use annotations.

  • First Aid: INHALATION: Call for medical aid. Remove to fresh air. If not breathing, give aritificial respiration. If breathing is difficult, give oxygen.; EYES: Flush eyes with copious amounts of water for at least 15 minutes.; SKIN: Wash with soap and copious amounts of water. (USCG, 1999) Source: CAMEO Chemicals
  • NFPA Health Rating: 2 - Materials that, under emergency conditions, can cause temporary incapacitation or residual injury. Source: Hazardous Substances Data Bank (HSDB)
  • NFPA Fire Rating: 2 - Materials that must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur. Materials would not under normal conditions form hazardous atmospheres with air, but under high ambient temperatures or under moderate heating could release vapor in sufficient quantities to produce hazardous atmospheres with air. Source: Hazardous Substances Data Bank (HSDB)
  • NFPA Instability Rating: 0 - Materials that in themselves are normally stable, even under fire conditions. Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Bioconcentration: An estimated BCF of 3.1 was calculated for methyl acetatoactate(SRC), using an estimated log Kow of -0.69(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC). Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Fate: TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 1.0(SRC), determined from a structure estimation method(2), indicates that methyl acetoacetate is expected to have very high mobility in soil(SRC). Volatilization of methyl acetoacetate from moist soil surfaces is expected to be slow(SRC) given an estimated Henry's Law constant of 2.7X10-7 atm-cu m/mole(SRC), derived from its vapor pressure of 0.892 mm Hg(3), and water solubility, 5X10+5 mg/L(4). A base-catalyzed second-order hydrolysis rate constant of 0.57 L/mole-sec(SRC) was estimated using a structure estimation method(5); this corresponds to half-lives of 140 and 14 days at pH values of 7 and 8, respectively(5). Methyl acetoacetate would be expected to hydrolyze in moist soil under basic conditions(SRC). Methyl acetoacetate is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.892 mm Hg(3). One screening test observed 78% biodegradation of methyl acetoacetate in 14 days(6); although this study was not specific to soil, it suggests that biodegradation in soil may be rapid(SRC). Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Fate: AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 1.0(SRC), determined from a structure estimation method(2), indicates that methyl acetoacetate is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected to be slow(3) based upon an estimated Henry's Law constant of 2.7X10-7 atm-cu m/mole(SRC), derived from its vapor pressure of 0.892 mm Hg(4), and water solubility, 5X10+5 mg/L(5). A base-catalyzed second-order hydrolysis rate constant of 0.57 L/mole-sec(SRC) was estimated using a structure estimation method(6); this corresponds to half-lives of 140 and 14 days at pH values of 7 and 8, respectively(6). According to a classification scheme(7), an estimated BCF of 3.1(SRC), from an estimated log Kow of -0.69(8) and a regression-derived equation(9), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Fate: ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), methyl acetoacetate, which has a vapor pressure of 0.892 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase methyl acetoacetate is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 5 days(SRC), calculated from its rate constant of 3.25X10-13 cu cm/molecule-sec at 25 °C(3). Methyl acetoacetate does not absorb light with wavelengths >290 nm(4) and is not expected to be susceptible to direct photolysis by sunlight(SRC). Source: Hazardous Substances Data Bank (HSDB)

Mapped by: Existing checksum-valid CAS to unique PubChem CID match. Retrieved: 2026-08-31. Open source record

Scientific classifications and hazard annotations provide context and do not replace the market-specific regulatory decision shown above.

Additional source coverage and match status
SourceResultChecked
EMBL-EBI ChEBIExact match2026-08-31
NIH PubChem PUG-ViewExact match2026-08-31

A recorded no-match is useful evidence that the source was checked; it is not a claim that the substance does not exist elsewhere.

Retrieved from NIH PubChem on 2026-08-31 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Records for CAS 105-45-3

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How CAS 105-45-3 is used on this site

CAS 105-45-3 is the Chemical Abstracts Service identifier used to pin this page to a specific substance. In the current dataset, 0 EU annex records share this identifier, which helps you cross-check whether the same substance appears under one regulatory context or several.

Use this page when a supplier specification, SDS or raw-material dossier gives you CAS 105-45-3 and you need to see every linked Annex II–VI record in one place. The entry cards above are the quickest route to concentration limits, warnings, annex placement and product-type conditions.