[C:1]([OH:8])(=[O:7])/[CH:2]=[CH:3]\[C:4]([OH:6])=[O:5].[OH-:9].[Na+].[CH2:11]([NH2:14])[CH2:12][NH2:13].Cl>O>[CH2:11]([NH:14][CH:3]([C:4]([OH:6])=[O:5])[CH2:2][C:1]([OH:7])=[O:9])[CH2:12][NH:13][CH:2]([C:1]([OH:8])=[O:7])[CH2:3][C:4]([OH:6])=[O:5]A beaker was charged with maleic acid (120.5 g, 1.03 mole); deionized water (120 g); and 50 percent aqueous NaOH (167 g, 2.08 mole). The mixture was stirred until dissolution occurred; the resulting solution was transferred to a 1-liter, stainless-steel autoclave, using 40 g deionized water as a rinse. Ethylenediamine (31.0 g, 0.51 mole) was added over a ten-minute period; and the autoclave was sealed. The mixture was stirred and heated at 140° C. for nine hours and then allowed to cool to ambient temperature. The product solution was acidified to a pH of about 2 with 37 percent aqueous HCl, resulting in the precipitation of racemic/meso EDDS acid. When the precipitation was complete, the product was removed by filtration; washed with deionized water (2×300 mL); and dried overnight under vacuum at 60° C. The yield of EDDS acid, shown to be pure by 1H- and 13C-nmr, was 108 g (0.37 mole, 72 percent).
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