Hydrogen Bonding in 2-Methyl-1,2,3-propanetricarboxylic Acid, Ammonium Dihydrogen 1,2,3-Propanetricarboxylate Hemihydrate and Tetraammonium 1,2,3,4-Butanetetracarboxylate Monohydrate

The extensive hydrogen-bonded networks of the title compounds, C₇H₁₀O₆, (I), NH₄⁺.C₆H₇O₆^-.1/2H₂O, (II), 4NH₄⁺.C₈H₆O₈^4-.H₂O, (III), have been analyzed. In compound (I), layers are formed by eight-membered and 16-membered hydrogen-bonded rings. In compound (II), the anions are arranged into double chains of 30-membered rings through short hydrogen bonds. These chains are cross-linked by weaker hydrogen bonds to H₂O and NH₄⁺. In compound (III), stacks of centrosymmetric anions are connected by hydrogen bonds to H₂O and NH₄⁺.