Although the results of nitration of benzenephosphonic acid have been reported, lv2 the esters of this acid have not been subjected to this reaction. A study of the aromatic reactions of such esters is of importance because of the ready availability of these derivatives by the modified Friedel-Crafts rea~ tion.~ In addition, the observations on the possible effect of the ester grouping, in comparison with the free acid, may be expected to be of interest.
