Crotonaldehyde

Crotonaldehyde is a chemical compound with the formula CH₃CH=CHCHO. The compound is usually sold as a mixture of the E- and Z-isomers, which differ with respect to the relative position of the methyl and formyl groups. The E-isomer is more common. This lachrymatory liquid is moderately soluble in water and miscible in organic solvents. As an unsaturated aldehyde, crotonaldehyde is a versatile intermediate in organic synthesis. It occurs in a variety of foodstuffs, e.g. soybean oils.^[4]

Crotonaldehyde^[1]

Names
IUPAC name (2E)-but-2-enal
Other names Crotonaldehyde Crotonic aldehyde β-Methacrolein β-Methyl acrolein 2-butenal Propylene aldehyde
Identifiers
CAS Number	4170-30-3 (E/Z) Y 123-73-9 (E) Y 15798-64-8 (Z) Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:41607 Y
ChEMBL	ChEMBL1086445 Y
ChemSpider	394562 Y
DrugBank	DB04381 Y
ECHA InfoCard	100.021.846
EC Number	204-647-1
IUPHAR/BPS	6288
KEGG	C19377 N
PubChem CID	447466
RTECS number	GP9499000
UNII	9G72074TUW (E/Z) Y 6PUW625907 (E) Y RB9WCA91QT (Z) Y
UN number	1143
CompTox Dashboard (EPA)	DTXSID8024864
InChI InChI=1S/C4H6O/c1-2-3-4-5/h2-4H,1H3/b3-2+ Y Key: MLUCVPSAIODCQM-NSCUHMNNSA-N Y InChI=1/C4H6O/c1-2-3-4-5/h2-4H,1H3/b3-2+ Key: MLUCVPSAIODCQM-NSCUHMNNBQ
SMILES O=C/C=C/C
Properties ((E) isomer)
Chemical formula	C4H6O
Molar mass	70.091 g·mol−1
Appearance	colourless liquid
Odor	pungent, suffocating odor
Density	0.846 g/cm3
Melting point	−76.5 °C (−105.7 °F; 196.7 K)
Boiling point	104.0 °C (219.2 °F; 377.1 K)
Solubility in water	18% (20 °C)[2]
Solubility	very soluble in ethanol, ethyl ether, acetone soluble in chloroform miscible in benzene
Vapor pressure	19 mmHg (20 °C)[2]
Refractive index (nD)	1.4362
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H301, H310, H311, H315, H318, H330, H335, H341, H373, H400
Precautionary statements	P201, P202, P210, P233, P240, P241, P242, P243, P260, P261, P262, P264, P270, P271, P273, P280, P281, P284, P301+P310, P302+P350, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P312, P314, P320, P321, P322, P330, P332+P313, P361, P362, P363, P370+P378, P391, P403+P233, P403+P235, P405, P501
NFPA 704 (fire diamond)	4 3 2
Flash point	13 °C (55 °F; 286 K)
Autoignition temperature	207 °C (405 °F; 480 K)
Explosive limits	2.1–15.5%
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	600 ppm (rat, 30 min) 1375 ppm (rat, 30 min) 519 ppm (mouse, 2 hr) 1500 ppm (rat, 30 min)[3]
LCLo (lowest published)	400 ppm (rat, 1 hr)[3]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 2 ppm (6 mg/m3)[2]
REL (Recommended)	TWA 2 ppm (6 mg/m3)[2]
IDLH (Immediate danger)	50 ppm[2]
Related compounds
Related alkenals	Acrolein cis-3-hexenal (E,E)-2,4-Decadienal
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Production and reactivity

Crotonaldehyde is produced by the aldol condensation of acetaldehyde:

2 CH₃CHO → CH₃CH=CHCHO + H₂O

Crotonaldehyde is a multifunctional molecule that exhibits diverse reactivity. It is a prochiral dienophile.^[5] It is a Michael acceptor. Addition of methylmagnesium chloride produces 3-penten-2-ol.^[6]

Uses

Crotonylidene diurea is a specialty fertilizer.^[7]

It is a precursor to many fine chemicals. A prominent industrial example is the crossed aldol condensation with diethyl ketone to give trimethylcyclohexenone, this can be easily converted to trimethylhydroquinone, which is a precursor to the vitamin E.^[8] Other derivatives include crotonic acid, 3-methoxybutanol and the food preservative Sorbic acid. Condensation with two equivalents of urea gives a pyrimidine derivative that is employed as a controlled-release fertilizer. ^[4]

Safety

Crotonaldehyde is a potent irritant even at the ppm levels. It is not very toxic, with an LD₅₀ of 174 mg/kg (rats, oral).^[4]

See also

• Crotyl
• Crotonic acid
• Crotyl alcohol
• Methacrolein