Binding of glyphosate by open-chain polyammonium cations

✍ Scribed by Lorenzo Abate; Concetta De Stefano; Claudia Foti; Silvio Sammartano

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 102 KB
• Volume: 18
• Category: Article
• ISSN: 0730-7268
• DOI: 10.1002/etc.5620181003

✦ Synopsis

Interaction of glyphosate (N-(phosphonomethyl)-glycine) with six polyamines (ethylendiamine, cadaverine, putrescine, triethylenetetramine, spermine, and tetraethylenepentamine) was studied potentiometrically. Several species of different stoichiometry are formed in the various systems, according to the general formation reaction

(where A ϭ amine and glp ϭ glyphosate). The complex species formed are always A(glp)H r (r Ϫ 3) with r ϭ 1 . . . (n ϩ 2) (n ϭ maximum degree of protonation of amines). The stability of various complexes is a linear function of charges involved in the formation reaction, and can be expressed as logK ij ϭ 0.9(Ϯ0.2) (where ϭ i[3 Ϫ j]). From the temperature dependence of formation constants, ⌬H 0 (and T⌬S 0 ) values have been obtained. Formation percentages of mixed glyphosate-polyammonium cation complexes are relevant also in low concentration conditions, and this means that these species may play a significant role in the speciation of natural fluids containing the reactants.