STRONG-ACID, CARBOXYL-GROUP STRUCTURES IN FULVIC-ACID FROM THE SUWANNEE RIVER, GEORGIA .2. MAJOR STRUCTURES

Polycarboxylic acid structures that account for the strong-acid charac teristics (pK(a1) near 2.0) were examined for fulvic acid from the Suw annee River. Studies of model compounds demonstrated that pK, values n ear 2.0 occur only if the alpha-ether or alpha-ester groups were in cy clic structures with two to three additional electronegative functiona l groups (carboxyl, ester, ketone, aromatic groups) at adjacent positi ons on the ring. Ester linkage removal by alkaline hydrolysis and dest ruction of ether linkages through cleavage and reduction with hydriodi c acid confirmed that the strong carboxyl acidity in fulvic acid was a ssociated with polycarboxylic alpha-ether and alpha-ester structures. Studies of hypothetical structural models of fulvic acid indicated pos sible relation of these polycarboxylic structures with the amphiphilic and metal binding properties of fulvic acid.