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Chemical Fact Sheet

Chemical Abstract Number (CAS #) 123739
CASRN 123-73-9
SynonymsCrotonaldehyde, (E)
2-Butenal, (E)-
Analytical Methods EPA Method 554
EPA Method 8315
Molecular FormulaC4H6O

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use CHEM INT FOR N-BUTYL ALCOHOL, QUINALDINE, CROTONIC ACID, SURFACE-ACTIVE AGENTS, TEXTILE & PAPER SIZES, INSECTICIDES & FLAVORING AGENTS; FUEL-GAS WARNING AGENT; SOLVENT FOR POLYVINYL CHLORIDE; ALCOHOL DENATURANT; LEATHER TANNING AGENT
Boiling Point 104 DEG C
Melting Point -74 DEG C
Molecular Weight 70.09
Density 0.869 AT 20 DEG C/20 DEG C
Odor Threshold Concentration Odor detection in air 5.25X10 2 ppb (gas chromatically pure) Odor low: 0.1050 mg/cu m; Odor high: 3.0000 mg/cu m
Sensitivity Data Crotonaldehyde vapor is so highly irritant to the eyes that people are unable to remain in the presence of dangerous concn IDLH 400 mg/cu m/; at 45 ppm the odor is extremely obnoxious & there is considerable eye discomfort. Its strongly lacrimatory vapors make it a valuable warning agent. Its most pronounced feature is its irritating effect on the nose, pharynx, & larynx.
Environmental Impact Crotonaldehyde (both the trans- and cis-isomers) is released to the atmosphere from the combustion of wood, polymers, and tobacco, in gasoline, diesel, and turbine engine exhausts, and in volcanic gases. If released to the atmosphere, trans-crotonaldehyde degrades rapidly (typical half-life of 11 hours) via reaction with photochemically produced hydroxyl radicals. If released to water in low concentrations, crotonaldehyde can degrade via reaction with photochemically produced oxidants (estimated half-life of 5 days) and volatilize (estimated half-lives of 40 hours from a model river one meter deep and 18.3 days from a pond). If released to soil, crotonaldehyde is susceptible to significant leaching. Evaporation from dry surfaces can be expected to occur. If released to the environment in a spill situation, a significant fraction of the spill may polymerize. The general population may be exposed to crotonaldehyde through inhalation of tobacco smoke, gasoline and diesel engine exhausts, and wood combustion. Occupational exposure via inhalation and dermal contact is possible at sites of its commercial production and use.
Environmental Fate TERRESTRIAL FATE: Crotonaldehyde is expected to leach in soil based on estimated Koc values of 6-50. Its relatively high vapor pressure of 30 mm Hg at 20 deg C indicates that evaporation from terrestrial surfaces may occur relatively rapidly. One screening study suggests that crotonaldehyde may be biodegradable, but data are insufficient to predict the importance of biodegradation in the environment. Crotonaldehyde readily polymerizes; therefore, if it is released to soil in a spill situation, a significant fraction may polymerize. AQUATIC FATE: When present in water in low concentrations, crotonaldehyde can be degraded by photochemically produced oxidants and transported to the atmosphere via volatilization. In sunlit natural water, olefinic structures (similar to crotonaldehyde) decompose via hydroxyl radicals and singlet oxygen at a combined half-life rate of about 5 days(1,SRC). Estimated volatilization half-lives are 40 hours for a model river (1 meter deep) and 18.3 days for an environmental pond(2,3). One screening study suggests that crotonaldehyde may be biodegradable, but data are insufficient to predict the importance of biodegradation in the environment. Aquatic hydrolysis, bioconcentration, and adsorption to sediment are not significant. If released in a spill situation, a significant fraction of the crotonaldehyde may polymerize. ATMOSPHERIC FATE: Crotonaldehyde is expected to exist almost entirely in the vapor-phase in the ambient atmosphere , based on a vapor pressure of 30 mm Hg at 20 deg C(1,SRC). trans-Crotonaldehyde reacts rapidly in the vapor-phase (typical half-life of 11 hours) with photochemically produced hydroxyl radicals. Reaction with ozone also occurs, but the rate (average half-life of 15.5 days) is not significant in comparison to hydroxyl radical reaction.
Drinking Water Impact DRINKING WATER: Crotonaldehyde (isomer not reported) has reportedly been identified in a drinking water sample (source and concn not reported) . Crotonaldehyde (steric form not reported) has reportedly been identified in a drinking water sample from the US (concn not reported) . EFFL: Crotonaldehyde (steric form not reported) was detected in 1 (concn <10ppb) of 6 US industrial effluents . A photographic industry wastewater effluent was found to contain crotonaldehyde . Crotonaldehyde concns of 0.006-0.116 g/kg were detected in emissions from wood burning fireplaces . Crotonaldehyde has been detected in exhausts from both gasoline and diesel engines .

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