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Name: Diethyl Maleate
Synonyms: DEM, Maleic acid diethyl ester
Chemical Formula: C8H12O4
CAS Number: 141-05-9
Common Uses: Found in chemical synthesis, pharmaceuticals, and as a plasticizer for various polymers. In many labs, it sits on the same shelf as common esters, joining organic chemists’ everyday toolkit for reactions needing a mild electrophile.
Hazard Class: Skin and eye irritant based on documented cases
Signal Word: Warning
Pictograms: Exclamation mark for irritant
Routes of Exposure: Reports point to skin contact, eye splashes, and accidental inhalation
Symptoms: Redness, itching, irritation if it gets on skin or in eyes; sneezing and coughing if inhaled
Chronic Risks: Studies note that ongoing exposure can dry the skin or aggravate pre-existing conditions. Safe handling reduces those risks, which matters for anyone working daily in a formulation lab.
Main Ingredient: Diethyl Maleate
Purity: Usually above 98% in industrial use
Impurities: Contains trace amounts of diethyl fumarate, a geometric isomer, sometimes seen in GC-MS reports. The low impurity levels point to consistent batch quality needed by chemists who expect predictable outcomes in scaled reactions.
Skin Contact: Wash thoroughly with soap and plenty of water. Peel off contaminated clothing right away.
Eye Contact: Flush eyes with clean water for at least 15 minutes, lifting eyelids to ensure thorough rinsing
Inhalation: Get the person to fresh air, monitor breathing, and seek medical attention if symptoms persist.
Ingestion: Rinse mouth, do not induce vomiting, and ask for medical advice. Each action steps from established chemical first aid protocols, recognizing the risks even mild esters present if mishandled.
Extinguishing Media: Use foam, dry chemical, or CO2 extinguishers
Combustion Products: Releases carbon monoxide, carbon dioxide, and possibly other toxic gases
Fire Hazards: Diethyl maleate is flammable, and its vapors may travel to an ignition source. Experience in a university setting showed how quickly small vapor concentrations ignite in an unventilated spot.
Advice for Firefighters: Equip with full protective gear and a self-contained breathing apparatus to reduce risk of chemical inhalation during a fire.
Personal Precautions: Wear gloves and goggles; provide adequate ventilation at all times
Environmental Precautions: Do not allow spills into sewers or natural waters. I have watched minor spills escalate due to poor drainage, contaminating floors and raising cleanup costs.
Clean-up Methods: Absorb liquid with sand or inert material, then collect in sealable containers. Ventilate the area and clean thoroughly to avoid leftover contamination.
Safe Handling: Use only in areas with good airflow, avoid direct bodily contact, never eat or smoke while handling
Storage Conditions: Store in tightly closed containers in a cool, dry place away from direct sunlight and incompatible chemicals. One tip that saves trouble is using secondary containment bins, lowering the risk of accidental leaks reaching workbenches.
Incompatibles: Keep away from oxidizers and strong bases, which can trigger dangerous reactions.
Engineering Controls: Use fume hoods or local exhausts to trap vapor
Protective Equipment: Wear safety goggles, chemical-resistant gloves, and lab coats. Those of us working in shared spaces know gloves alone do not always cut it—embedded vapors in clothing can linger and cause irritation.
Hygiene Measures: Wash hands after handling and before eating or touching your face.
Appearance: Clear colorless or slightly yellow liquid
Odor: Mild ester-like smell
Boiling Point: Around 229°C
Melting Point: -60°C
Flash Point: Around 107°C
Solubility: Moderately soluble in water, miscible with organic solvents
Vapor Pressure: Low at room temperature
Density: 1.08 g/cm³ at 20°C
Viscosity: Thin, free-flowing ester.
Chemical Stability: Stable in normal conditions if kept away from acids, bases, and oxidizing agents
Conditions to Avoid: Heat, flame, static electricity, and direct sunlight
Hazardous Polymerization: Not known to polymerize easily, but heating above boiling point can cause decomposition
Decomposition Products: Carbon monoxide, carbon dioxide, maleic acid derivatives if overheated or burned
Likely Routes: Skin, lungs, eyes, ingestion
Acute Toxicity: Moderate—skin and eye irritation widely documented; ingestion causes nausea and abdominal pain
Chronic Effects: Extended contact dries skin, animal studies warn of possible liver impact at high doses, but standard laboratory precautions minimize risks. Throughout my years, quick washing and proper gear have prevented long-term issues in shared lab environments.
Aquatic Toxicity: Hazardous to aquatic life in concentrated spills. Species tests show reduced reproduction rates in fish and daphnia glyp.
Persistence: Not especially persistent, but breaks down faster under sunlight and with certain bacteria
Bioaccumulation: Low bioaccumulation noted in field and lab tests
Soil Mobility: Moves in loose soil, but bonds somewhat in clay-rich environments
Waste Treatment: Collect liquid waste for disposal by licensed chemical hazardous waste handlers
Contaminated Packaging: Rinse triple, then dispose of according to local hazardous waste regulations. Large-scale users, like universities, emphasize labeled drums and scheduled pickups to avoid storage mishaps that have plagued smaller labs.
Sewage Disposal: Never pour down the drain, as even minor organic esters disrupt biological treatment and foul up municipal systems.
UN Number: 1145 for shipping
Proper Shipping Name: Diethyl Maleate
Transport Hazard Class: 3 (flammable liquid)
Packing Group: III
Special Precautions: Transport in secure, upright containers; avoid stacking to prevent leaks in transit. Freight companies with experience in chemicals tend to have fewer incidents, based on industry reviews.
Safety Regulations: Subject to workplace safety labeling and handling requirements; falls under OSHA and GHS standards for irritants
Community Right-to-Know: Not listed as a major toxic release but flagged for prudent handling
Use Restrictions: Only trained staff in qualified laboratories or manufacturing sites
International Status: Recognized in EU under REACH registration for industrial chemicals
Waste Minimization: Facilities are expected to implement best practices that reduce waste and exposure according to environmental guidelines, a point every responsible organization faces not only for compliance but for ethical stewardship in an industry with evolving standards.
