Originator
Triclos,Merrell National,US,1972
Manufacturing Process
Trichloroethanol (500 grams) and phosphorus oxychloride (510 grams) were
added to dry diethyl ether (3.5 liters) and stirred at 10°C with ice/water
cooling. Dry pyridine (270 ml) was added dropwise over 1 hour, maintaining
the temperature below 25°C. The resulting suspension was stirred for a
further 1 hour and then stood at 0°C overnight. The pyridine hydrochloride
was removed by filtration and washed with diethyl ether (2 x 300 ml) and
dried in vacuo over P2O5 to give 380 grams.
The ether filtrate and washings were evaporated at room temperature under
reduced pressure to give a clear liquid residue (801 grams). This residue was
distilled under high vacuum to give trichloroethyl phosphorodichloridate (556
grams, 62.4% of theory), boiling point 75°C/0.8 mm.
The phosphorodichloridate was hydrolyzed by adding to a stirred solution of
sodium carbonate (253 grams) in water (2.9 liters). After 1 hour the solution
was cooled and acidified with a solution of concentrated sulfuric acid (30 ml)
in water (150 ml) and then extracted with a mixture of tetrahydrofuran and
chloroform (2.3/1; 3 x 1 liter). The tetrahydrofuran/chloroform liquors were
bulked and evaporated to dryness to give a light brown oil. This was dissolved
in water (1 liter) and titrated with 2 N sodium hydroxide solution to a pH of
4.05 (volume required 930 ml). The aqueous solution was clarified by filtration
through kieselguhr and then evaporated under reduced pressure to a syrup
(737 grams).
Hot acetone (4.5 liters) was added to this syrup and the clear solution stood
at room temperature for 2 hours and then at 0°C overnight. The white
crystalline solid was filtered off, washed with acetone (2 x 400 ml) and dried
at 60°C in vacuo to give sodium trichloroethyl hydrogen phosphate (414
grams, 49.3% of theory from trichloroethanol).
