Chelating properties of n,n,n,n-tetrakis-(phosphonomethyl)-1,2-cyclohexanediamine

The octasodium salt of N,N,N',N'-tetrakis-(phosphonomethyl)-1,2-cyclohoxanediamine, Na₈-CDTMP, can be prepared in 45% yield from chloromethylphosphonic acid and 1,2-cyclohexanediamine. The titration curve resulting from the titration of the acid, CDTMP, with sodium hydroxide at 25° and μ = 0.1 was used to estimate the eight pK values for the free acid. The stability constants of metal chelatles of CDTMP were measured at 25° and μ = 0.1 potentiometrically.