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Preparation and Structure of Magnesium Bis(hydrogen β ‐glutamate) Hexahydrate
Author(s) -
Wiesbrock Frank,
Nogai Stefan,
Schier Annette,
Schmidbaur Hubert
Publication year - 2002
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(200204)85:4<1151::aid-hlca1151>3.0.co;2-p
Subject(s) - chemistry , potentiometric titration , magnesium , aqueous solution , hydrogen bond , inorganic chemistry , glutamic acid , dissociation (chemistry) , titration , hydrogen , crystal structure , coordination sphere , ion , crystallography , amino acid , molecule , organic chemistry , biochemistry
The dissociation equilibria of aqueous solutions of β ‐glutamic acid were studied by potentiometric titration and the three p K values determined under standard conditions. The hydrogen β ‐glutamate anion β ‐GluH − was found to be the dominating species in the physiologically relevant pH range 4.0–9.4. Neutralization of β ‐glutamic acid by magnesium oxide affords magnesium bis(hydrogen β ‐glutamate) Mg ( β ‐GluH) 2 , which crystallizes as the hexahydrate from dilute aqueous solution. A single‐crystal X‐ray study showed that the β ‐GluH − anions are not part of the coordination sphere of the magnesium ion. Instead hexahydrated dications [Mg(H 2 O) 6 ] 2+ are intimately associated with free β ‐GluH − anions through a three‐dimensional network of H‐bonds. This study provides the first structural and conformational reference data for the β ‐GluH − anion.