(Hexamethylphosphoric triamide, HMPA, HMPT)

CAS 680-31-9



(Me2N)3P = O


Physical Properties

Colorless liquid

bp 233 °C, mp 6 °C

Completely miscible with water



Spicy odor (no threshold data)


Vapor Density

6.2 (air = 1.0)


Vapor Pressure

0.07 mmHg at 25 °C


Flash Point

105 °C


Toxicity Data

LD50 oral (rat)

2525 mg/kg


LD50 skin (rabbit)

2600 mg/kg

Major Hazards

Possible human carcinogen (OSHA "select carcinogen")


The acute toxicity of hexamethylphosphoramide is low. HMPA can cause irritation upon contact with the skin and eyes.

Hexamethylphosphoramide has been found to cause cancer in laboratory animals exposed by inhalation and meets the criteria for classification as an OSHA "select carcinogen." Chronic exposure to HMPA can cause damage to the lungs and kidneys. Reproductive effects in male animals treated with hexamethylphosphoramide have been observed. HMPA should be regarded as a substance with poor warning properties.

Flammability and Explosibility

Combustible liquid. Its decomposition at high temperatures or in a fire can produce phosphine, phosphorus oxides, and oxides of nitrogen, which are extremely toxic. Carbon dioxide or dry chemical extinguishers should be used for HMPA fires.

Reactivity and Incompatibility

Incompatible with strong oxidizing agents and strong acids.

Storage and Handling

Because of its carcinogenicity, hexamethylphosphoramide should be handled using the "basic prudent practices" of Chapter 5.C, supplemented by the additional precautions for work with compounds of high chronic toxicity (Chapter 5.D). In particular, this compound should be handled only in a fume hood, using appropriate impermeable gloves and splash goggles to prevent skin and eye contact. Containers of this substance should be stored in secondary containers.

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