The composition of the crystal of tri-3-pyridylmethanol monohydrate (1•H2O) has been determined by the elemental analysis, thermogravimetric analysis (TGA), and X-ray crystallographic analysis. In the crystal of 1•H2O, the oxygen atom of water forms the hydrogen bond with O-H proton of 1, whereas both two hydrogen atoms of water form the hydrogen bonds with the nitrogen atom of 1. Tri-3-pyridylmethanol (1) is one of the promising precursors to tetra-3-pyridylmethane. Wibaut et al. synthesized

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... the reaction of 3-lithiopyridine, generated in situ from 3-bromopyridine by the treatment with n-butyllithium, with ethyl nicotinate or di-3-pyridylketone in 1950's (Scheme 1). [1] They found that 1 dissolved in alkali as well as in acid and determined the acid dissociation constant of 1. In their intensive investigation of 1, they encountered the difficulty in obtaining the crystal of 1 without moisture. Although they reported that the result of the elemental analysis for was "anomalous", the data of the elemental analysis was not presented. This contrasted the fact that tri-2-and tri-4pyridylmethanol were obtained as crystalline substance without moisture and their elemental analyses were not anomalous. [1] Several conformers of 1 based on the rotation of 3-pyridyl groups within a small energy range may prevent 1 from crystallizing. On the other hand, the water molecules may form the hydrogen bonds with 1 to crystallize as hydrate. We have disclosed that the composition of the hydrated crystal of 1 is 1•H2O by the elemental analysis, thermogravimetric analysis (TGA), and X-ray crystallographic analysis. Furthermore, the hydrogen bonds between 1 and water molecule in 1•H2O have also been revealed by X-ray crystallographic analysis. Scheme 1. Synthesis of tri-3-pyridylmethanol (1).