High yields of bis‐(dialkoxyphosphonyl‐methyl)‐ phosphinic esters, (RO)2 (O)‐PCH2P(O)OR, bis‐(aloxyphosphinyl‐methyl)‐phosphinic esters, [R(RO)(O)PCH2]2P(O)OR, are obtained by heating bis‐chloromethyl‐phosphinic esters, (CICH2)2P(O)OR, with alkylphoshites, phosphonites and phosphinites, repectively, at 170 to 180°C for several hours. Hydrolysis of these esters in achieved by refluxing with conc. HCl for extended periods.
Bis‐(dihydroxyphosphonyl‐methyl)‐phosphinic acid, HO(O)P[CH2P(O) (OH)2]2, obtained by hydrolysis of the all‐ethyl ester, titrates in aqueous solution as a tetrabasic acid with breaks at pH = 5,2 (three equivalents) and at pH = 8,8 (one equivalent). The fifth proton can be titrated only after addition of NaCl. This acid is an excellent chelating agent for metal ions.
The 1H‐ and 31P‐NMR. spectra of all the compounds prepared are discussed.