Organogels from Carbohydrate Amphiphiles

Gluconamides can be easily functionalized to give a variety of compounds that form organogels with a high viscosity. N - n -octyl- d -gluconamide-6-benzoate gelates a large variety of organic solvents, including 1,2-xylene, chloroform, ethyl acetate, and ethanol, to form gels which are, in some cases, stable even above the boiling point of the pure solvent. The 2-methoxy, 6-imidazolyl, 6-acetyl, and 6-cyclohexanoyl derivatives also show gelation, but the 2,4;3,5-dimethylene-protected derivatives do not. Detailed 1 H NMR, IR, and X-ray powder diffraction studies reveal that the molecules of most gelators are packed in a head-to-tail fashion. If there is, however, the possibility to form inter -layer hydrogen bonds, as in the case of N - n -octyl- d -gluconamide or N - n -octyl- d -gluconamide-6-(3-pyridyl carboxylate), the molecules are packed head-to-head. Some gluconamides, e.g., those with aliphatic substituents, express their molecular chirality in the supramolecular structures, whereas others, in particular those containing a large aromatic substituent on carbon atom C 6, yield nonchiral aggregates, probably due to interfering π−π stacking interactions of the substituents. DSC experiments show that the formation of the gels is an entropy-driven process.