title: Complexation of Al(III) with gluconate in alkaline to hyperalkaline solutions: formation, stability and structure.
abstract: Contrary to suggestions in the literature, it has been proven that Al(III) forms a 1 : 1 complex with gluconate (hereafter Gluc(-)) in strongly alkaline (pH > 12) aqueous solutions. The complex formation was proven via(27)Al and (1)H NMR, freezing-point depression, polarimetric measurements as well as potentiometric and conductometric titrations. This complexation is a pH independent process, i.e., a condensation reaction takes place. The stability constant of the complex formed was derived from (1)H NMR and polarimetric measurements, and was found to be log K = 2.4 ± 0.4. In the complex formed, Al(III) has a tetrahedral geometry, and the Al(OH)4(-) is most probably statistically distributed between the alcoholate groups of the Gluc(-).
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged, H-6720, Hungary.
authors.forename: Attila
authors.initials: A
authors.lastname: Pallagi
authors.forename: Ágost Gyula
authors.initials: ÁG
authors.lastname: Tasi
authors.forename: Gábor
authors.initials: G
authors.lastname: Peintler
authors.forename: Péter
authors.initials: P
authors.lastname: Forgo
authors.forename: István
authors.initials: I
authors.lastname: Pálinkó
authors.forename: Pál
authors.initials: P
authors.lastname: Sipos
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D005942:Gluconates / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry*; D012996:Solutions
chemical_list: D005942:Gluconates; D009942:Organometallic Compounds; D012996:Solutions; D012972:Sodium Hydroxide; D000535:Aluminum; C030691:gluconic acid