Methylammonium hydrogen maleate

O- -H bonds in the anion, the negative region of the Laplacian is not shared by the VSCCs of either of the 0-atoms. Similar situations are found for symmetric intermolecular O- H O HBs realized in the crystal structures of methylam-monium hydrogen succinate monohydrate [89] and methylammonium hydrogen maleate [90] considerable covalent signal (V p cp < 0) for the O -H interactions, without shared VSCCs with the 0-atoms. 

D. Madsen, C. Flensburg and S. Larsen, Properties of the experimental crystal density of methylammonium hydrogene maleate. A salt with very short intramolecular O-H- O hydrogen bond, / Phys. Chem. A102, 2177-2188 (1998). 

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