Formaldehyde → N-(Carboxymethyl)-N-(phosphonomethyl)glycine

Participants

Reaction Conditions

Reaction Steps

Water (11.2 g, 0.623 moles) was charged to a 500 ml three neck flask fitted with thermometer, condenser, dropping funnel and stirrer. The stirrer was started and phosphorous acid (42.6 g, at 99%; 0.514 moles) was added whereupon the temperature dropped from 20° C. to 12° C. Sulphuric acid (49.8 g at 98%, 0.498 moles) was then added over 10 minutes whilst maintaining the temperature below 50° C. with a water bath. Iminodiacetic acid (66.5 g at 95.4% strength, 0.479 moles) was then added to the reaction flask. The reaction mixture was heated to 115° C. and formaldehyde (48.2 g at 37.0% strength, 0.594 moles) was added over two hours. The temperature was maintained between 110° and 120° C. during addition. On complete addition, the reaction mixture was held at 115° C. for a furthre hour and then allowed to cool to 90° C. A second water charge (92.0 g) was added over 1 hour maintaining the temperature at approximately 90° C. during the addition. The reaction mixture was allowed to self-cool overnight. The slurry was filtered, washed with cold water (57.0 g) and the resulting product was dried at 60° C. in a vacuum oven overnight to give 100.2 g of N-phosphonomethyliminodiacetic acid at 95.7% strength, equivalent to an isolated yield of 88.1%. The filtrates (172.8 g) and the water wash (71.7 g) contained 4.8% and 1.2% N-phosphonomethyliminodiacetic acid respectively. This gave a total conversion yield of 93.5% N-phosphonomethyliminodiacetic acid.

Provenance & Evidence