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In industrial chemistry, polymer synthesis, and organic intermediate synthesis, Carbonic dichloride (Phosgene / Carbonyl chloride), defined by the molecular formula CCl₂O, is a reactive and highly toxic organic compound belonging to the class of carbonyl halides.
Carbonic dichloride exists as a colorless liquid at low temperatures, and as a colorless, heavy gas with an odor reminiscent of freshly cut grass or moldy hay at room temperature and pressure.
Carbonic dichloride is primarily used in the chemical industry as a strategic reagent in the synthesis of isocyanates, which are the main components of polyurethane production, in the manufacture of polycarbonate plastics, and in the preparation of pesticide and pharmaceutical intermediates.
CAS Registry Number: 75-44-5.
EC / EINECS Number: 200-870-3.
PubChem CID: 6371.
UN Dangerous Goods Number: UN 1076 (Class 2.3 Toxic Gas, Subsidiary Risk 8 Corrosive).
Molecular Weight: 98.92 g/mol.
Synonyms: Carbonic dichloride, Carbonyl chloride, Phosgene, Carbon oxychloride, Carbon oxide dichloride, Carbonyl dichloride, Dichloromethanone, Chloroformyl chloride, Carbonic acid dichloride, COCl₂.
Basic Properties, Physicochemistry, and Identifiers
Density: Liquid density at 0 °C is 1.432 g/cm³; gas density (relative to air) is 3.41 (significantly heavier than air).
Melting Point: -127.8 °C.
Boiling Point: 8.2 °C.
Flash Point: Non-flammable (Does not ignite, but forms toxic decomposition products under high heat).
Vapor Pressure: 161.8 kPa (1.6 atm) at 20 °C.
Solubility in Water: Insoluble in water; rapidly hydrolyzes upon contact with water to form carbon dioxide (CO₂) and hydrochloric acid (HCl).
Solubility in Organic Solvents: Soluble in benzene, toluene, xylene, chloroform, acetic acid, and chlorinated hydrocarbons.
Thermal Decomposition: Carbonic dichloride decomposes at high temperatures into carbon monoxide (CO) and chlorine (Cl₂) gases.
Food Additive Status: Carbonic dichloride is strictly unsuitable as a food additive or for human consumption (It has no E-number).
Production Processes and Chemical Synthesis
Carbonic dichloride is produced on an industrial scale by the exothermic reaction of purified carbon monoxide (CO) and chlorine (Cl₂) gases in the presence of an active carbon catalyst.
The hot gas mixture leaving the reactor is gradually cooled to liquefy crude Carbonic dichloride and is transferred to the purification unit.
Carbonic dichloride is brought to ultra-high purity via cryogenic distillation and stored as a liquefied gas inside high-security closed-loop systems, or directly fed into consumption reactors.
Applications and Industrial Uses
The largest industrial application of Carbonic dichloride is the synthesis of methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), which are raw materials for polyurethane foam, flexible sponges, and coatings.
Carbonic dichloride is reacted with Bisphenol A (BPA) to produce high-impact polycarbonate plastics widely used in the automotive, electronics, and optics sectors.
Carbonic dichloride is evaluated as a reagent in the synthesis of chloroformate and isocyanate intermediates for the production of carbamate group insecticides and herbicides.
Carbonic dichloride is used in the pharmaceutical industry as an acylating agent in the synthesis of active pharmaceutical ingredients (APIs), carbamates, and carbonate esters.
Carbonic dichloride serves as a strategic functional group transfer agent in specialized organic synthesis, dye intermediates, and synthetic fiber chemical synthesis.
Safety, Toxicology, and Storage Standards
According to GHS standards, Carbonic dichloride is classified as Fatal if Inhaled (Acute Toxicity Inhalation Category 1), Causes Severe Skin Burns and Eye Damage (Category 1B), and Gas Under Pressure.
Carbonic dichloride possesses extremely high pulmonary toxicity; when inhaled, Carbonic dichloride slowly hydrolyzes with water in the pulmonary alveoli to form HCl, and this Carbonic dichloride-induced condition leads to delayed pulmonary edema, respiratory failure, and death.
Both gas and liquid forms of Carbonic dichloride cause tissue destruction in the eyes and skin, severe chemical burns, and necrosis.
Carbonic dichloride is subject to strict international protocols regarding chemical weapons and toxic gases; Carbonic dichloride must only be used in fully sealed closed systems with continuous gas detector monitoring.
Carbonic dichloride reacts violently and exothermically with water, moisture, alcohols, amines, strong bases, and ammonia.
Carbonic dichloride rapidly corrodes metals in moist environments.
Carbonic dichloride must be stored in cool, dry, exceptionally ventilated areas, connected to gas scrubber systems, and kept within specially approved steel pressure vessels.
