Hydroxymethanediphosphonic acid

In the alkyl chain hydroxy groups or side chains may be present. The reaction is somewhat different when acyl halides are used. Hydroxymethanediphosphonic acid is prepared by reacting phosgene with an alkali metal, dialkyl phosphite. The reaction is rapid and exothermic. The temperature is controlled between 10 and 20°C. After hydrolysis with HC1, hydroxymethanediphosphonic acid is recovered [91,92]. 

The following reaction sequence was used to obtain methyl hydroxymethanediphosphonic acid. This compound is widely used as a water hardness sequestering agent and detergent builder. Triethyl chloride was reacted with acetyl chloride to give diethylacetylphosphonate, followed by a conversion with diethyl phosphite and sodium. After completion of this reaction the substance was hydrolyzed with HC1 to yield hydroxymethanediphosphonic acid, [93,94], as shown in Eqs. (49)-(51) ... 

---