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Nerve Agent Precursors: Alkyl phosphites
(Dimethyl phosphite, Trimethyl phosphite, Diethyl phosphite, Triethyl phosphite)

CA Index Name Phosphonic acid, dimethyl ester Phosphorous acid, trimethyl ester Phosphonic acid, diethyl ester Phosphorous acid, triethyl ester
CAS Registry Number 868-85-9
121-45-9
 762-04-9 122-52-1
RTECS Number SZ7710000
TH1400000
   TH1130000
Synonyms
  • Bis(hydroxymethyl)phosphine oxide
  • Dimethoxyphosphine oxide
  • Dimethyl acid phosphite
  • Dimethyl hydrogen phosphite
  • Dimethyl hydrogen phosphonate
  • Dimethyl phosphate
  • Dimethyl phosphonate
  • Dimethyl phosphorous acid
  • Hydrogen dimethyl phosphate
  • Methyl phosphonate
  • Phosphorous acid dimethyl ester
  • Trimethoxyphosphine
  • Trimethyl phosphite
  • Ethyl phosphite
  • Diethoxy phosphine oxide
  • Diethyl acid phosphite
  • Diethyl hydrogen phosphite
  • Diethyl phosphite
  • Diethyl phosphonate
  • Hydrogen diethyl phosphite
  • O,O-Diethyl phosphonate
  • Ethyl phosphite
  • Triethoxyphosphine
  • Triethyl phosphite
  • Tris(ethoxy)phosphine
EINECS Number 212-783-8 204-471-5 212-091-6 204-552-5
UN Transport Code   2329   2323
ICSC Number       0684
CWC Schedule 3B

 

Warning symbols
Harmful

 

CHEMICAL AND PHYSICAL PROPERTIES

 

  Dimethyl phosphite Trimethyl phosphite Diethyl phosphite Triethyl phosphite
 
Appearance Colorless liquid
Clear liquid with a pungent, unpleasant odor.
Clear liquid with faint but distinctive smell. Clear liquid with distinctive and unpleasant smell.
Molecular
Formula		 C2H7O3P
C3H9O3P
 C4H11O3P C6H15O3P
Molecular
Weight		 110.06
124.09
138.1 166.16
Boiling
Point		 170°C
111° C
50°C (at 2mm Hg) 158°C
Melting
Point		  
-78° C
   
Liquid
Density		 1.2
1.046
1.072 0.96
Vapor
Density		  
4.3
   
Vapor pressure 8.5 kPa at 95°C      
Flammable

 

NFPA Hazard Ratings
 
FIRE
HEALTH
REACTIVITY

SPECIAL

Dimethyl phosphite * * * *
Trimethyl phosphite 3 3 2 *
Diethyl phosphite * * * *
Triethyl phosphite 2 2 2 *
*Nothing found or not listed.

Also refer to 2000 Emergency Response Guidebook (ERG2000) Guide 129 for responses to triethyl phosphite and trimethyl phosphite.

 


Initial Isolation and Protective Action Distances

There are no specific recommendations for initial isolation distances for alkyl phosphites other than an informal recommendation to clear an area within approx. 1 km of a major spill or fire involving alkyl phosphites.

Health Hazards

All of these alkyl phosphites are harmful irritants. They can cause eye, skin and pulmonary (lung) irritation. The irritation is reversible with proper cleaning of the affected site and suitable follow-up treatment. At high concentrations, irritation of the lungs can cause edema (filling of the lungs with fluid) that can lead to death by asphyxiation. Chronic exposure may lead to long term problems including emphysema and liver and kidney damage. Environmental air limits are set at 10 mg/m3 per 10 hour day. There is evidence that they are carcinogenic and teratogenic.

Risk and Safety Phrases.

Trimethyl phosphite Diethyl phosphite
  • R20 - Harmful by inhalation.
  • R21-Harmful in contact with skin.
  • R22 -Harmful if swallowed.
  • R45 - May cause cancer.
  • R46 - May cause heritable genetic damage.
  • S16 - Keep away from sources of ignition.
  • S26 - In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.
  • S36 - Wear suitable protective clothing.
  • S37 - Wear suitable gloves.
  • S39 - Wear eye / face protection.
  • S45 - In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)
  • R36 - Irritating to eyes.
  • R37 - Irritating to respiratory system.
  • R38 - Irritating to skin.
  • S26 - In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.
  • S36 - Wear suitable protective clothing.
  • S37 - Wear suitable gloves.
  • S39 - Wear eye / face protection.

INDUSTRIAL/COMMERCIAL USES

Alkyl phosphites are versatile reagents and are manufactured in the US, Europe, and Asia. Industrial uses include:

 

COMMENTS

Alkyl phosphites are used in the manufacture of G-type nerve agents. They are relatively easy to manufacture by the reaction of phosphorus trichloride and an alcohol: methanol for the methyl phosphites and ethanol for the ethyl phosphites. As phosphorus trichloride and the alcohols have a worldwide manufacture in the hundreds of thousands to millions of tons, policing the synthesis of the alkyl phosphites is a challenge to proliferation control.

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