1H-NMR Karplus Analysis of Molecular Conformations of Glycerol under Different Solvent Conditions: A Consistent Rotational Isomerism in the Backbone Governed by Glycerol/Water Interactions

Abstract

Glycerol is a symmetrical, small biomolecule with high flexibility in molecular conformations. Using a 1H-NMR spectroscopic Karplus analysis in our way, we analyzed a rotational isomerism in the glycero backbone which generates three kinds of staggered conformers, namely gt (gauche-trans), gg (gauche-gauche), and tg (trans-gauche), at each of sn-1,2 and sn-2,3 positions. The Karplus analysis has disclosed that the three rotamers are consistently equilibrated in water keeping the relation of ‘gt:gg:tg = 50:30:20 (%)’ at a wide range of concentrations (5 mM~540 mM). The observed relation means that glycerol in water favors those symmetric conformers placing 1,2,3-triol groups in a gauche/gauche geometry. We have found also that the rotational isomerism is remarkably changed when the solvent is replaced with DMSO-d6 or dimethylformamide (DMF-d7). In these solvents, glycerol gives a relation of ‘gt:gg:tg = 40:30:30 (%)’, which means that a remarkable shift occurs in the equilibrium between gt and tg conformers. By this shift, glycerol turns to also take non-symmetric conformers orienting one of the two vicinal diols in an antiperiplanar geometry.

Microstructure and performance modification of PVDF ultrafiltration membrane via adjusting the composition of coagulation Bath

“…Due to its abundant hydroxyl groups, glycerol can reduce the intermolecular forces between polymer chains, thereby overcoming membrane brittleness and increasing the flowability of polymer chains. 23 A general glycerol treatment in membrane separation technology referred to immersing prepared membranes in a certain concentration of glycerol to prevent pore shrinkage or collapse. 24 In order to simplify the membrane production process, glycerol was added to the solidification bath.…”

“…Glycerol, as a symmetrical small biomolecule, is an important component in the production of plasticized flexible membranes. Due to its abundant hydroxyl groups, glycerol can reduce the intermolecular forces between polymer chains, thereby overcoming membrane brittleness and increasing the flowability of polymer chains 23 . A general glycerol treatment in membrane separation technology referred to immersing prepared membranes in a certain concentration of glycerol to prevent pore shrinkage or collapse 24 .…”