Abstract
Two of the constituent mol-ecules in the title structure, 2C6H7N2O+·HPO32-·H2O, i.e. the phosphite anion and the water mol-ecule, are situated on a symmetry plane. The mol-ecules are held together by moderate N-H⋯O and O-H⋯N, and weak O-H⋯O and C-H⋯Ocarbon-yl hydrogen bonds in which the amide and secondary amine groups, and the water molecules are involved. The structural features are usual, among them the H atom bonded to the P atom avoids hydrogen bonding.
Highlights
Two of the constituent molecules in the title structure, 2C6H7N2O+ÁHPO32ÀÁH2O, i.e. the phosphite anion and the water molecule, are situated on a symmetry plane
The structural features are usual, among them the H atom bonded to the P atom avoids hydrogen bonding
It is difficult to predict which of these two forms would be prefererred, because of a small difference of ÁpKa = pKa(base) À pKa(acid) (Childs et al, 2007). [The pKa values for 3-carbamoylpyridine and H3PO3 are 3.3 and 1.3, respectively (CRC Handbook, 2009).]
Summary
Nicotinamide (pyridine-2-carboxamide) is a biologically important molecule, being the active part of vitamin B3 and nicotinamide adenine dinucleotide (NAD) (e.g. Wald, 1991; Williamson et al, 1967). Nicotinamide (pyridine-2-carboxamide) is a biologically important molecule, being the active part of vitamin B3 and nicotinamide adenine dinucleotide (NAD) Wald, 1991; Williamson et al, 1967). Interest in the preparation of the title hydrated salt was called for with respect to an investigation of the configuration of the –NH2 group and its dependence on its environment. It was hoped that 3-carbamoylpyridine (nicotinamide) would make a salt or a co-crystal with phosphorous acid, H3PO3. It is difficult to predict which of these two forms would be prefererred, because of a small difference of ÁpKa = pKa(base) À pKa(acid) (Childs et al, 2007). [The pKa values for 3-carbamoylpyridine and H3PO3 are 3.3 and 1.3 (first degree), respectively (CRC Handbook, 2009).]
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