GB703181A - Alkylene diamine methylene phosphonic acids - Google Patents

Abstract

The invention comprises as new compounds those having the formula:- <FORM:0703181/IV(b)/1> wherein Alk represents an alkylene radical (CnH2n) containing from two to six carbon atoms, R is hydrogen or <FORM:0703181/IV(b)/2> , and R1 is hydrogen or <FORM:0703181/IV(b)/3> and the alkali metal salts of said compounds. The compounds may be prepared by reacting a halo-methylphosphonic acid salt with an alkylene diamine containing from two to six carbon atoms in alkaline aqueous solution at elevated temperature. In this method, the alkylene diamine may be dissolved in water containing caustic alkali, e.g. sodium hydroxide, in an amount providing a pH of 10-11.5 and the solution heated to from 60 DEG C. to refluxing temperature and a halomethyl phosphonic acid salt in aqueous solution then added and the mixture boiled under reflux. In an example the tetramethylene phosphonic acid derivative of ethylene diamine is prepared by dissolving one molar weight of ethylene diamine in water, heating the solution to about 70 DEG C. and then adding a solution containing four mols of the disodium salt of chloromethyl phosphonic acid and an excess of a base such as sodium carbonate to maintain a pH of 10.0 to 11.5. The solution is then boiled under reflux, cooled, and a mineral acid such as hydrochloric acid added to reduce the pH to 6-7. The solution is then filtered, the filtrate evaporated to dryness, the dry residue taken up in water and the formed solution filtered and then treated with ethyl alcohol to precipitate the tetrasubstituted ethylene diamine. Alternatively, the latter may be precipitated by acidifying the solution with hydrochloric acid to a pH of about 1-2. When two of the phosphonic groups are fully neutralized to form the tetra-alkali metal salt the remaining phosphonic groups react as chelating groups for mono- and poly-valent metal ions without insolubilizing the compound. The octa sodium salts and other sodium salts representing less than full neutralization are also strong chelating agents for most polyvalent metals. The iron chelate obtained by reacting the tetra alkali metal salt of the ethylene diamine derivative in aqueous solution with freshly precipitated iron hydroxide (Fe(OH)3) and the copper chelate of the octa alkali metal salt of the same derivative are referred to. When three mols of halomethyl phosphonic acid salt are employed per mol. of ethylene diamine the product contains a mixture of ethylene diamine di-, tri-, and tetra-(methylene-phosphonic acid) compounds and when two mols of the former reagent are employed per mol. of ethylene diamine a mixture of the mono-, di- and tri-substituted compounds is obtained which consists predominately of the di-substituted product. These intermediate products are also chelating agents but their chelating power is generally less than that of the tetra substituted compound. Thus a metal ion such as copper will combine preferentially with the latter when treated with a mixture of the di- and tetra-substituted compounds. The symmetrical alkylene diamine di(methylene phosphonic acid) compounds may also be prepared by reacting two mols of an alkali metal salt of amino-methyl phosphonic acid with one mol. of an alkylene dihalide containing from two to six carbon atoms, the reaction being carried out at elevated temperature in an aqueous solution having a pH not less than 7 and this reaction may be carried out under reflux in 50 per cent. ethanol. The N:N1 di-substituted ethylene diamine compound may also be obtained from hydroxymethyl phosphonic acid di-alkyl ester which is first converted to the chloromethyl derivative by treatment with hydrogen chloride, the chloromethyl derivative being treated with ethylene diamine in the ratio of two mols of the phosphonic ester per mol. of ethylene diamine to form the tetraalkyl ester which is then hydrolysed or saponified. Instead of ethylene diamine other alkylene diamines containing from two to six carbon atoms, e.g. propylene diamine or trimethylene diamine may also be employed.