NMR analysis of the iron ligand ethylenediaminedi(o-hydroxyphenyl)acetic acid (EDDHA) employed in fertilizers

The exceptional efficiency of the iron chelate of ethylenediaminedi(o-hydro xyphenyl)acetic acid (o,o-EDDHA) in correcting iron chlorosis in plants and the medical applications of various metallic chelates of this compound hav e long been recognized. As commercial preparations of o,o-EDDHA usually con tain impurities, a method for their detection is proposed. By using one- an d two-dimensional nuclear magnetic resonance two impurities were identified . The structure of one of these compounds was assigned to an isomer of EDDH A containing at least one p-hydroxyphenyl moiety. The structure of the othe r impurity was tentatively assigned to a byproduct of the EDDHA synthesis: 2,6-di[CH(COOH)NHCH2CH2NHCH(COOH)Ar] phenol (Ar = hydroxyphenyl). Both comp ounds were also detected in the EDDHA extracted from a commercial iron fert ilizer.