THEORETICAL-STUDIES ON THE STRUCTURE OF CHIRAL 1,2-DIOL SYSTEMS - MONOMERS, DIMERS AND MONOHYDRATES

The structures and stabilities of the isolated 1,2-propanediol (PDL1,2) monomers, dimers and monohydrates were investigated by the force field versions PIMM91 and GROMOS87 as well as the semiempirical PM3 method. The results on the PDL1,2 monomers are in agreement with ab initio data and gas phase experimental findings and show that the most stable conformers are stabilized by internal hydrogen bonding. The preferred structures of the dimers are characterized by the formation of additional intermolecular hydrogen bonds. Within the calculations dimers of PDL1,2 generated from the same (R-R) and different (R-S) enantiomers are taken into account. The aim of the investigations on the monohydrates of PDL1,2 was to study the function of water at the association of the 1,2-diol head groups in bilayers with a very simple model. Results on 1,3-propanediol are included for comparison. The different energetic and structural behaviours of both diol groups are discussed with respect to the formation of intramolecular and intermolecular hydrogen bonds.