X-ray mapping in heterocyclic design. I. Diffractometric study of crystalline 1,2-dihydro-2-imino-1-carboxymethylpyridine monohydrate: Structural evidence for the zwitterionic character of the molecule

A single-crystal X-ray diffraction analysis of 1,2-dihydro-2-imino-1-carboxymethylpyridine is carried out. The transparent colorless crystals are orthorhombic, and the unit-cell parameters are as follows: a=5.026(1) A, b=12.320(7) A, c=25.551(1) A, space group Pbca. The structure is solved and refined to R1=0.0562. In the six-membered heterocycle, the partially ordinary bonds alternate with the partially double bonds. The plane of the carboxylate group is almost perpendicular to the plane of the pyridine ring, and the existence of intramolecular hydrogen bonds becomes impossible. The crystal structure involves an extended system of intermolecular bonds, including those with the participation of water molecules