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CAS 123-73-9

CAS 123-73-9 matches 1 EU annex record across Annex II–VI of Regulation 1223/2009.

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Chemical identity and properties

PubChem 2D chemical structure for CAS 123-73-9
CAS 123-73-9PubChem CID 447466

Crotonaldehyde

IUPAC name
(E)-but-2-enal
Molecular formula
C4H6O
Molecular weight
70.09 g/mol
Exact mass
70.041864811 Da
XLogP3
0.5
Topological polar surface area
17.1 Ų
Hydrogen-bond donors
0
Hydrogen-bond acceptors
1
Covalent units
1
Defined stereocentres
0

Also known as

2-ButenalCrotonalCrotylaldehyde(2E)-but-2-enalCrotonic aldehydeMethylpropenal1-Formylpropenebeta-Methylacrolein
16 more reported names
Propylene aldehyde2-ButenaldehydeKrotonaldehydbeta-Methyl acrolein4170-30-3RCRA waste number U053trans-2-butenaldehydeUN 1143AI3-18303 (USDA)CHEBI:416079G72074TUW3-MethylacroleinNSC-56354RefChem:5709224-030-0trans-Crotonaldehyde
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External database identifiers

Evidence from additional scientific databases

NIH PubChem PUG-View
Exact identifier match447466

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

  • First Aid: Warning: Effects may be delayed. Caution is advised.; Signs and Symptoms of Crotonaldehyde Exposure: Acute exposure to crotonaldehyde may produce tearing and extreme irritation to skin, eyes and, upper respiratory tract. Corneal damage may occur. Respiratory signs may include delayed pulmonary edema.; Emergency Life-Support Procedures: Acute exposure to crotonaldehyde may require decontamination and life support for the victims. Emergency personnel should wear protective clothing appropriate to the type and degree of contamination. Air-purifying or supplied-air respiratory equipment should also be worn, as necessary. Rescue vehicles should carry supplies such as plastic sheeting and disposable plastic bags to assist in preventing spread of contamination.; Inhalation Exposure:; 1. Move victims to fresh air. Emergency personnel should avoid self-exposure to crotonaldehyde.; 2. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is detected, provide CPR. If not breathing, provide artificial respiration. If breathing is labored, administer 100% humidified oxygen or other respiratory support.; 3. Obtain authorization and/or further instructions fr Source: CAMEO Chemicals
  • First Aid: Warning: Crotonaldehyde, (E)- is an extreme eye, respiratory, and skin irritant and can cause corneal damage. Caution is advised.; Signs and Symptoms of Crotonaldehyde, (E)- Exposure: Signs and symptoms of acute exposure to crotonaldehyde, (E)- may include irritation of the eyes, skin, mucous membranes, nose, throat and upper respiratory tract. Delayed onset of pulmonary edema is possible following inhalation. Corneal damage may occur as may allergic contact dermatitis. Seizures may also be observed.; Emergency Life-Support Procedures: Acute exposure to crotonaldehyde, (E)- may require decontamination and life support for the victims. Emergency personnel should wear protective clothing appropriate to the type and degree of contami-nation. Air-purifying or supplied-air respiratory equipment should also be worn, as necessary. Rescue vehicles should carry supplies such as plastic sheeting and disposable plastic bags to assist in preventing spread of contamination.; Inhalation Exposure:; 1. Move victims to fresh air. Emergency personnel should avoid self-exposure to crotonaldehyde, (E)-.; 2. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is Source: CAMEO Chemicals
  • ERG2024, Guide 131P (Crotonaldehyde; Crotonaldehyde, stabilized): General First Aid:; · Call 911 or emergency medical service.; · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination.; · Move victim to fresh air if it can be done safely.; · Administer oxygen if breathing is difficult.; · If victim is not breathing:; -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance.; -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped with a one-way valve or other device).; -- If no pulse detected or no respiratory medical device available, provide continuous compressions. Conduct a pulse check every two minutes or monitor for any signs of spontaneous respirations.; · Remove and isolate contaminated clothing and shoes.; · For minor skin contact, avoid spreading material on unaffected skin.; · In case of contact with substance, remove immediately by flushing skin or eyes with running water for at least 20 minutes.; · For severe burns, immediate medical attention is required.; · Effects of exposure (inhalation, ingestion, Source: Emergency Response Guidebook (ERG)
  • First Aid: (General first aid procedures); Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately.; Skin: Water flush immediately - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. Get medical attention promptly.; Breathing: Respiratory support; Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately. Source: The National Institute for Occupational Safety and Health (NIOSH)
  • Signal: Danger Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • GHS Hazard Statements: H225: Highly Flammable liquid and vapor [Danger Flammable liquids]; H301: Toxic if swallowed [Danger Acute toxicity, oral]; H311: Toxic in contact with skin [Danger Acute toxicity, dermal]; H315: Causes skin irritation [Warning Skin corrosion/irritation]; H318: Causes serious eye damage [Danger Serious eye damage/eye irritation]; H330: Fatal if inhaled [Danger Acute toxicity, inhalation]; H335: May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation]; H341: Suspected of causing genetic defects [Warning Germ cell mutagenicity]; H373 **: May causes damage to organs through prolonged or repeated exposure [Warning Specific target organ toxicity, repeated exposure]; H400: Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard] Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • Precautionary Statement Codes: P203, P210, P233, P240, P241, P242, P243, P260, P261, P262, P264, P264+P265, P270, P271, P273, P280, P284, P301+P316, P302+P352, P303+P361+P353, P304+P340, P305+P354+P338, P316, P317, P318, P319, P320, P321, P330, P332+P317, P361+P364, P362+P364, P370+P378, P391, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement) Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • Signal: Danger Source: European Chemicals Agency (ECHA)
  • GHS Hazard Statements: H225 (100%): Highly Flammable liquid and vapor [Danger Flammable liquids]; H301 (100%): Toxic if swallowed [Danger Acute toxicity, oral]; H311 (91.8%): Toxic in contact with skin [Danger Acute toxicity, dermal]; H315 (99.1%): Causes skin irritation [Warning Skin corrosion/irritation]; H318 (99.7%): Causes serious eye damage [Danger Serious eye damage/eye irritation]; H330 (100%): Fatal if inhaled [Danger Acute toxicity, inhalation]; H335 (100%): May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation]; H341 (> 99.9%): Suspected of causing genetic defects [Warning Germ cell mutagenicity]; H373 (> 99.9%): May causes damage to organs through prolonged or repeated exposure [Warning Specific target organ toxicity, repeated exposure]; H400 (100%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard] Source: European Chemicals Agency (ECHA)
  • Precautionary Statement Codes: P203, P210, P233, P240, P241, P242, P243, P260, P261, P262, P264, P264+P265, P270, P271, P273, P280, P284, P301+P316, P302+P352, P303+P361+P353, P304+P340, P305+P354+P338, P316, P317, P318, P319, P320, P321, P330, P332+P317, P361+P364, P362+P364, P370+P378, P391, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement) Source: European Chemicals Agency (ECHA)
  • ECHA C&L Notifications Summary: Aggregated GHS information provided per 1784 reports by companies from 27 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.; Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website. Source: European Chemicals Agency (ECHA)
  • GHS Hazard Statements: H225 (100%): Highly Flammable liquid and vapor [Danger Flammable liquids]; H300 (10.8%): Fatal if swallowed [Danger Acute toxicity, oral]; H301 (100%): Toxic if swallowed [Danger Acute toxicity, oral]; H310 (11.2%): Fatal in contact with skin [Danger Acute toxicity, dermal]; H311 (99.6%): Toxic in contact with skin [Danger Acute toxicity, dermal]; H315 (100%): Causes skin irritation [Warning Skin corrosion/irritation]; H318 (94.2%): Causes serious eye damage [Danger Serious eye damage/eye irritation]; H330 (100%): Fatal if inhaled [Danger Acute toxicity, inhalation]; H335 (100%): May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation]; H341 (100%): Suspected of causing genetic defects [Warning Germ cell mutagenicity]; H373 (99.6%): May causes damage to organs through prolonged or repeated exposure [Warning Specific target organ toxicity, repeated exposure]; H400 (96.9%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard] Source: European Chemicals Agency (ECHA)
  • ECHA C&L Notifications Summary: Aggregated GHS information provided per 223 reports by companies from 11 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.; Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website. Source: European Chemicals Agency (ECHA)
  • Signal: Danger Source: NITE-CMC
  • GHS Hazard Statements: H225: Highly Flammable liquid and vapor [Danger Flammable liquids]; H340: May cause genetic defects [Danger Germ cell mutagenicity]; H350: May cause cancer [Danger Carcinogenicity]; H401: Toxic to aquatic life [Hazardous to the aquatic environment, acute hazard] Source: NITE-CMC
  • Precautionary Statement Codes: P203, P210, P233, P240, P241, P242, P243, P273, P280, P303+P361+P353, P318, P370+P378, P403+P235, P405, and P501 (click each P-code to see the statement) Source: NITE-CMC
  • NFPA Health Rating: 4 - Materials that, under emergency conditions, can be lethal. Source: Hazardous Substances Data Bank (HSDB)
  • NFPA Fire Rating: 3 - Liquids and solids that can be ignited under almost all ambient temperature conditions. Materials produce hazardous atmospheres with air under almost all ambient temperatures or, though unaffected by ambient temperatures, are readily ignited under almost all conditions. Source: Hazardous Substances Data Bank (HSDB)
  • NFPA Instability Rating: 2 - Materials that readily undergo violent chemical changes at elevated temperatures and pressures. Source: Hazardous Substances Data Bank (HSDB)
  • NFPA Specific Notice: W - No water: Materials that react violently or explosively with water. Source: Hazardous Substances Data Bank (HSDB)
  • Toxicity Summary: IDENTIFICATION AND USE: Crotonaldehyde is a water-white, mobile liquid. Crotonaldehyde was formerly used in the manufacture of n-butanol, but currently, the most extensive use of crotonaldehyde is in the manufacture of sorbic acid. Crotonaldehyde has also been used as a warning agent in fuel gases, in the preparation of rubber accelerators, in leather tanning, as an alcohol denaturant, and as a stabilizer for tetraethyl-lead. HUMAN STUDIES: A 15-minute exposure to crotonaldehyde at 4.1 ppm was highly irritating to the nose and upper respiratory tract and produced lacrimation in human volunteers in 30 seconds. Crotonaldehyde is highly toxic by the dermal route. Direct contact with liquid crotonaldehyde causes rapid and severe eye and skin irritation or burns. Exposure to vapor produces inflammation of mucous membranes. Clinical cases of sensitization have occurred. Crotonaldehyde vapors may produce pulmonary edema at high concentrations. Crotonaldehyde, a mutagen and carcinogen, reacts with deoxyguanosine (dGuo) in DNA to generate a pair of diastereomeric adducts (Cro-dGuo). Cro-dGuo adducts inhibit DNA synthesis and induce miscoding in human cells. DNA from human liver, lung, and b Source: Hazardous Substances Data Bank (HSDB)
  • Toxicity Summary: IDENTIFICATION AND USE: (E)-Crotonaldehyde is a liquid. It is used in the manufacture of butyl alcohol, butyraldehyde, methoxybutyraldehyde, sorbic acid, maleic acid, crotonic acid, crotyl alcohol. In polymer chemistry, it is used in the manufacture of resins and polyvinyl acetals, as a solvent for polyvinyl chloride, as a rubber antioxidant, and it increases rubber strength with ketones. It is also used in preparation of insecticides and fertilizers, and in production of flavors. HUMAN STUDIES: (E)-Crotonaldehyde is a lacrymating material that is very dangerous to the eyes. It is a human skin and respiratory system irritant. Individuals with chronic respiratory disease, impaired pulmonary function, obstructive airway diseases, or skin disease may be at an increased risk from exposure to crotonaldehyde. ANIMAL STUDIES: Reported LD50 ranged from 140 mg/kg in rabbit to 1331 mg/kg in guinea pig, and LC50 for inhalation in rat was 4000 mg/cu m per 30 min exposure. Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Bioconcentration: An estimated BCF of 3 was calculated in fish for crotonaldehyde(SRC), using an estimated log Kow of 0.60(1) and a regression-derived equation(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low. Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Bioconcentration: An estimated BCF of 3 was calculated in fish for (E)-crotonaldehyde(SRC), using an estimated log Kow of 0.60(1) and a regression-derived equation(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low. Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Fate: TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 2(SRC), determined from a structure estimation method(2), indicates that crotonaldehyde is expected to have very high mobility in soil(SRC). Volatilization of crotonaldehyde from moist soil surfaces is expected(SRC) given an estimated Henry's Law constant of 1.5X10-5 atm-cu m/mole(SRC), based upon its vapor pressure, 30 mm Hg(3), and water solubility, 1.81X10+5 mg/L(4). Crotonaldehyde is expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3). A 73% of Theoretical BOD using activated sludge in the Japanese MITI test(5) suggests that biodegradation is an important environmental fate process in soil(SRC). Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Fate: AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 2(SRC), determined from a structure estimation method(2), indicates that crotonaldehyde is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 1.5X10-5 atm-cu m/mole(SRC), derived from its vapor pressure, 30 mm Hg(4), and water solubility, 1.81X10+5 mg/L(5). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 2.1 and 18 days, respectively(SRC). Crotonaldehyde is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(3). According to a classification scheme(6), an estimated BCF of 3(SRC), from an estimated log Kow of 0.60(2) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low. The half-lives for olefinic structures (similar to crotonaldehyde) in sunlit natural waters are about 13 and 8 days with respect to reaction via hydroxyl radicals and singlet oxygen(7). Crotonaldehyde was observed to hav 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), crotonaldehyde, which has a vapor pressure of 30 mm Hg at 20 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase crotonaldehyde 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 11 hours(SRC), calculated from an experimental rate constant for trans-crotonaldehyde of 3.6X10-11 cu cm/molecule-sec(3) and an estimated rate constant for cis-crotonaldehyde of 3.6X10-11 cu cm/molecule-sec(SRC) that was derived using a structure estimation method(4). The atmospheric reaction half-life of crotonaldehyde with ozone is estimated to be 6.3 and 12 days for the trans- and cis-isomers, respectively, based on estimated reaction rates of 1.8X10-18 and 9.1X10-19 cu cm/molecule-sec at 25 °C(SRC), derived using a structure estimation method(4), and an atmospheric concentration of 7X10+11 ozone molecules per cu cm(5). Crotonaldehyde absorbs at wavelengths >290 nm(6) and, therefore, may be susceptible to direct photolysis by sunlight(SRC). Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Fate: TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 2(SRC), determined from a structure estimation method(2), indicates that (E)-crotonaldehyde is expected to have very high mobility in soil(SRC). Volatilization of (E)-crotonaldehyde from moist soil surfaces is expected(SRC) given a Henry's Law constant of 1.94X10-5 atm-cu m/mole(3). (E)-Crotonaldehyde is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 38 mm Hg at 25 °C(4). A 73% of Theoretical BOD using activated sludge in the Japanese MITI test(5) suggests that biodegradation is an important environmental fate process in soil(SRC). Other biodegradation studies suggest that (E)-crotonaldehyde may be biodegradable in soil(6), especially in anaerobic conditions(7,8). Source: Hazardous Substances Data Bank (HSDB)
  • Environmental Fate: AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 2(SRC), determined from a structure estimation method(2), indicates that (E)-crotonaldehyde is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon a Henry's Law constant of 1.94X10-5 atm-cu m/mole(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 40 hours and 15 days, respectively(SRC). (E)-Crotonaldehyde is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(3). According to a classification scheme(5), an estimated BCF of 3(SRC), from an estimated log Kow of 0.60(2) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low. Biodegradation studies suggest that (E)-crotonaldehyde may be biodegradable in water(6), especially in anaerobic conditions(7,8). 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), (E)-crotonaldehyde, which has a vapor pressure of 38 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase (E)-crotonaldehyde is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals and ozone(SRC); the half-lives for these reactions in air are 11 hours and 15.5 days(SRC), calculated from respective rate constants of 3.6X10-11(3) and 7.4X10-19(4) cu cm/molecule-sec. (E)-Crotonaldehyde contains chromophores that absorb at wavelengths >290 nm(5) and, therefore, may be susceptible to direct photolysis by sunlight(SRC). Source: Hazardous Substances Data Bank (HSDB)
  • Sources/Uses: Used in the synthesis of other organic chemicals; [ACGIH] Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
  • Sources/Uses: Used to make other chemicals (n-butyl alcohol, quinaldine, crotonic acid, 2-ethylhexyl alcohol, butyraldehyde, surface-active agents, resins, rubber antioxidants, textile and paper sizes, insecticides, and flavoring agents); Also used as a fuel-gas warning agent, solvent for polyvinyl chloride and purification of mineral oils, alcohol denaturant, leather tanning agent, to locate breaks and leaks in pipes, and in chemical warfare; [HSDB] Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
  • Industrial Processes with risk of exposure: Petroleum Production and Refining [Category: Industry]; Leather Tanning and Processing [Category: Industry] Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
  • Uses: For crotonaldehyde (USEPA/OPP Pesticide Code: 202600) there are 0 labels match. /SRP: Not registered for current use in the U.S., but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./ Source: Hazardous Substances Data Bank (HSDB)
  • Uses: Crotonaldehyde was formerly used in the manufacture of n-butanol, but currently, the most extensive use of crotonaldehyde is in the manufacture of sorbic acid. Crotonaldehyde has also been used as a warning agent in fuel gases, in the preparation of rubber accelerators, in leather tanning, as an alcohol denaturant, and as a stabilizer for tetraethyl-lead. Source: Hazardous Substances Data Bank (HSDB)
  • Uses: Manufacture of butyl alcohol, butyraldehyde, methoxybutyraldehyde, sorbic acid, maleic acid, crotonic acid, crotyl alcohol. In polymer chemistry: manufacture of resins and polyvinyl acetals, solvent for polyvinyl chloride, rubber antioxidant, increases rubber strength with ketones. In prepatation of insecticides and fertilizers. In production of flavors. Source: Hazardous Substances Data Bank (HSDB)
  • Uses: Intermediate for n-butyl alcohol and 2-ethylhexyl alcohol, solvent, preparation of rubber accelerators, purification of lubricating oils, insecticides, tear gas, fuel-gas warning agent, organic synthesis, leather tanning, alcohol denaturant. Source: Hazardous Substances Data Bank (HSDB)
  • Uses: 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 Source: Hazardous Substances Data Bank (HSDB)
  • Uses: Manufacture of butyl alcohol, butyraldehyde, methoxybutyraldehyde, sorbic acid, maleic acid, crotonic acid, crotyl alcohol. In polymer chemistry: manufacture of resins and polyvinyl acetals, solvent for polyvinyl chloride, rubber antioxidant, increases rubber strength with ketones. In prepatation of insecticides and fertilizers. In production of flavors. /Crotonaldehyde/ 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.

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

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