threshold activity the analogous derivatives of the adducts of aminoethylpiperazine and urea are quite effective the compounds from which the methylenephosphonates are derived have the formula str8 wherein a is str9 or hydrogen and where m is 0 2 and n is 2 or 3 these compounds are made by reacting urea with an aminohydrocarbylpiperazine thus for example aminoethylpiperazine 516 84 g 4 moles was added to a 1 liter reaction vessel equipped with a stirrer reflux condenser temperature control and indicating means was added 516 84 g 4 moles of aminoethylpiperazine aep after raising the temperature to about 120 u00b0 c 0 32 g 0 0039 mole of 2 methylimidazole catalyst was added immediately followed by the addition of 20 g 0 3 mole of urea after reacting for 2 hours at 120 u00b0 c while stirring another 0 32 g 0 0039 mole of 2 methylimidazole catalyst was added followed by the addition of 40 g 0 7 moles of urea the progress of the reaction was monitored periodically by titration with 1nhcl employing bromthymol blue as an indicator the titration results after 54 3 hours was the same as that after 17 4 hours at 120 u00b0 c the excess aminoethyl piperazine was removed by means of a rotoevaporator at a temperature of 120 u00b0 c and a pressure.