Acrolein
Properties
| State | Liquid (volatile) |
| Color | Colorless to yellowish |
| Solubility | Soluble in water (208 g/L at 20°C); miscible with organic solvents |
| Melting Point | -87°C |
| Boiling Point | 53°C |
About Acrolein
Acrolein is the smallest α,β-unsaturated aldehyde, and that structural fact — a carbonyl conjugated with a vinyl group on three carbons total — is responsible for almost everything that's interesting and unpleasant about the molecule. The conjugation makes it the textbook Michael acceptor: the β-carbon carries enough electrophilic character that any soft nucleophile (thiols, amines, carbanions) attacks it readily, generating a 1,4-addition product. The same chemistry that makes acrolein useful in synthesis is what makes it dangerous in vivo, where it reacts indiscriminately with cysteine and lysine residues on proteins and damages tissue at concentrations well below the smell threshold. Industrial production runs over 500,000 tonnes per year, almost all of it via gas-phase oxidation of propylene over a bismuth molybdate catalyst, and almost all of the output is captured immediately as the precursor to acrylic acid (the next oxidation step) without ever being isolated as bulk acrolein. The standalone applications are smaller-scale: methionine synthesis (which feeds animal nutrition at industrial scale), 1,3-propanediol, glutaraldehyde, and water-treatment biocides. The molecule also forms spontaneously when fats overheat past their smoke point — that sharp, eye-watering haze rising from a too-hot frying pan is acrolein, plus a few other unsaturated aldehydes from glycerol decomposition.
Where you'll encounter it
If you've ever burned cooking oil and felt your eyes sting from across the room, that was acrolein — the molecule forms readily when triglycerides overheat past their smoke point and the glycerol backbone dehydrates. It's also a major component of cigarette smoke and one of the standard toxicology endpoints when measuring oxidative damage from lipid peroxidation. In a clinical context, acrolein is the cyclophosphamide metabolite that causes hemorrhagic cystitis — patients on that chemotherapy regimen receive mesna alongside it specifically to scavenge the acrolein in the bladder before it can react with the urothelium. In a synthesis lab, acrolein-related chemistry is what students learn first when introduced to conjugate addition; the parent compound itself is rarely handled because of the toxicity, but the Michael-acceptor pattern it embodies is everywhere in organic chemistry.
Common Uses
- Captive intermediate for industrial acrylic acid production
- Methionine synthesis for poultry and livestock feed
- Aquatic-systems and irrigation-channel biocide
- Glutaraldehyde and 1,3-propanediol synthesis
- Reference Michael acceptor in mechanistic chemistry teaching
Safety Information
Acutely toxic by every route — inhalation, skin contact, and ingestion all carry severe risks. The vapor is lachrymatory at sub-ppm concentrations and corrosive to mucous membranes; sustained exposure damages lung tissue. Highly flammable (flash point -26 °C). GHS pictograms span H225, H300, H311, H314, H330, and H400. Handle in a fume hood with proper PPE; this is one of the few common reagents where the smell threshold is well below the toxic threshold, so trust the gauges, not your nose.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.