© 2026 Sinochem Nanjing Corporation,
All Right Reserved
Name: Propiolic acid
Chemical Formula: HC≡C–COOH
CAS Number: 471-25-0
Description: Propiolic acid stands out in the laboratory with its sharp, acrid smell and colorless, oily appearance. People involved in organic chemistry often come across it because of its triple-bonded carbon structure, which makes it reactive and somewhat unpredictable on the bench.
Hazards: Corrosive to skin and eyes, flammable vapor, severe respiratory hazard, can affect the nervous system during prolonged exposure, and forms hazardous fumes such as carbon monoxide under fire conditions. Its volatility and the risk of rapid vapor formation often catch folks off guard, which is why the focus stays on ventilation and containment.
Hazard Symbols: Corrosive, Flammable, Harmful
Routes of Exposure: Inhalation, skin absorption, ingestion.
Risk Phrases: Causes burns, harmful if inhaled or swallowed, serious risk of irreversible effects on skin and mucous membranes.
Chemical: Propiolic acid, purity usually above 97% in standard preparations.
Impurities: Acetic acid, water, trace alkyne derivatives—these amplify reactivity and can lead to variable toxicity or unexpected reactions if overlooked in synthetic setups.
Inhalation: Remove person to fresh air right away. Monitor for cough, wheezing, or delayed breathing issues. If symptoms persist, seek emergency medical attention.
Skin Contact: Flush contaminated skin using copious amounts of water. Remove clothes and accessories that could trap liquid. Check for lingering redness or blistering, as these can hint at deeper tissue damage.
Eye Contact: Flush eye with water for at least 15 minutes, rolling the eyeball to ensure coverage.
Ingestion: Rinse mouth. Do not provoke vomiting. Medical staff should get involved as soon as possible because of the potential for mucosal burns.
Clinical Considerations: Chemical burns from propiolic acid require fast, aggressive care—experience shows delays compound injury, so speed matters most.
Suitable Extinguishing Media: Carbon dioxide, dry chemical powder, alcohol-resistant foam.
Fire Hazards: Vapors ignite easily at room temperature, and decomposition releases carbon monoxide and acrid smoke. Heat sources should stay isolated from storage.
Protective Equipment: Self-contained breathing apparatus and full protective suit—propiolic acid fumes can leave lasting injury to eyes, throat, and lungs.
Special Advice: Removing containers from fire zone requires judgment and backup, as explosions may follow if handling slips.
Personal Precautions: Shield exposed skin, use goggles, put on NIOSH-approved respirator. Experienced lab workers say slipping into a splash suit is a must, not a formality.
Environmental Precautions: Contain spills away from drains and soil. Propiolic acid trickling into waterways spells long-term toxicity for aquatic life.
Cleanup Methods: Absorb spill with inert material like vermiculite, shovel residues into tightly sealed hazardous waste containers. Minor releases get neutralized with soda ash before final disposal.
Handling: Use in chemical fume hood. Keep away from open flames, static charge build-up, and incompatible chemicals, especially bases and strong oxidizers. Direct user experience always points out how even seasoned professionals should avoid working alone.
Storage: Keep containers tightly closed, store in cool, dry, ventilated area, outside direct sunlight. Glass containers with Teflon-lined seals stay preferred, as typical plastics sometimes deform under contact.
Incompatibilities: Bases, amines, strong oxidizers—mixing with these can trigger violent reactions or degradation.
Engineering Controls: Chemical fume hood, explosion-proof ventilation.
Personal Protection: Safety goggles, chemical-resistant gloves (nitrile or butyl), flame-resistant lab coat, full face shield for larger scale handling.
Respiratory Protection: Organic vapor respirator if handling outside of fume hood proves unavoidable.
Hygiene Measures: Wash hands thoroughly after use, avoid eating or drinking in the work area, use disposable towel for skin contact cleanup.
Exposure Limits: No specific OSHA or ACGIH limits for propiolic acid, but adopt same standards as other corrosive, volatile organics.
Appearance: Colorless, oily liquid
Odor: Pungent, acrid
Melting Point: -23°C
Boiling Point: 80°C
Density: 1.036 g/cm³
Solubility: Miscible with water; higher volatility near boiling point means strong fumes quickly form in open containers. The sharp odor provides instant warning of leaks or spills.
Stability: Stable in tightly closed containers at room temperature. Exposure to bases or oxidizing agents initiates rapid, sometimes exothermic decomposition.
Reactive Conditions: Heat, open flames, incompatible chemicals.
Hazardous Decomposition: Carbon monoxide, carbon dioxide, acrid organic vapors.
Polymerization: Does not self-polymerize under normal conditions, but small traces of catalysts provoke runaway reactions—one of the reasons for cautious supervision during synthetic work.
Acute Effects: Powerful skin and eye irritant, corrosive upon contact, inhalation causes coughing, chest pain, and sometimes delayed pulmonary edema. Workers exposed chronically report headaches and confusion likely tied to nervous system involvement.
Chronic Effects: Prolonged or repeated skin contact produces dermatitis and skin cracking.
Routes of Exposure: Absorption especially pronounced via respiratory and digestive tracts.
Animal Data: Animal studies confirm corrosive properties, with delayed tissue damage more common than for related short-chain carboxylic acids.
User Perspective: Even in low doses, improper handling leaves a real mark on skin and respiratory passages, so respect for protective gear usually grows after folks witness an exposure incident.
Aquatic Toxicity: Toxic to aquatic organisms, with both acute and chronic risks documented in the literature—breakdown products linger and accumulate in sensitive environments.
Persistence and Degradability: Limited data, but alkynes in general resist rapid breakdown, raising concerns about long-term buildup.
Bioaccumulation: Not expected to bioaccumulate in higher organisms, though breakdown intermediates might pose risks for bottom-dwelling life.
Environmental Precautions: Spill control is a must, as many practitioners learn the hard way that even small leaks spell trouble for lab drains.
Disposal Methods: Incineration at specialized hazardous waste facilities. Neutralization with dilute base, followed by dilution and professional disposal, aligns with experience as the safest lab-scale approach.
Container Disposal: Triple rinse containers, then offer for chemical waste collection—landfilling without cleaning presents risks of lingering corrosion or fire.
User Note: Those who skip proper disposal measures often face not just regulatory penalties, but also hidden costs from injury and environmental damage.
UN Number: 2929
Hazard Class: 6.1 (Toxic substances), 8 (Corrosive substances)
Packing Group: II
Transport Precautions: Ship in corrosion-resistant packaging, clearly label with hazard class, and avoid bulk transport unless trained to handle chemical emergencies.
Personal Experience: Extra caution pays off during transit; even a well-sealed sample can leak if packaging isn’t robust.
Global Inventories: Listed in key international chemical inventories, including TSCA (US), DSL (Canada), and others.
Labeling & Classification: Classified as hazardous under chemical safety regulations owing to acute toxicity, corrosion, and flammability. Labelling laws force sellers and users alike to mark packages with visible warning symbols and response guidance.
PPE Regulations: National workplace safety bodies direct the use of gloves, goggles, and ventilation controls based on documented exposure risks.
Community Impact: Local environmental protection agencies monitor for releases, reflecting a concern for downstream water quality and accidental releases during disposal or transport.
