The role of H-bonding in the structure of the 4-piperidinecarboxylic acid monohydrate

In this work we have investigated the hydrogen bond scheme of 4-piperidinecarboxylic (isompecotic) acid by means of X-ray diffraction, NMR spectroscopy and semi-empirical calculations. The 4-piperidinecarboxylic acid displays a three-dimensional assembly of hydrogen bonds. Hence, infinite chains of amino acid molecules linked by amino-carboxylate intermolecular hydrogen bonds run parallel to the b and c axes; additionally, chains of amino acid molecules intercalated with water molecules held together by water-carboxylate hydrogen bonds run parallel to the a axis. The theoretical calculations show large cooperative effects for the first of the amino acid chains mentioned above, which is manifested as shortening on the aminocarboxylate hydrogen bond distances and decreasing of the hydrogen bond enthalpies per monomer of the hydrogen bonded clusters, with increment of monomers in the chain. (C) 2002 Elsevier Science B.V. All rights reserved.