THE X-RAY CRYSTAL-STRUCTURE OF N-(1-HEXADECYL)-D-GLUCONAMIDE AND POWDER DIFFRACTION STUDIES ON ITS LOWER AND HIGHER HOMOLOGS (N=9-18)

The crystal structure of N-(1-hexadecyl)-D-gluconamide [a = 4.8072(6) Angstrom b = 46.771(5) Angstrom, c = 5.2885(7) Angstrom, beta = 94.37(1)degrees; monoclinic P2(1), Z = 2] displays the same molecular conformation and the same monolayer packing-arrangement as its lower homologues described previously. This is at seeming variance with most recent CPMAS (13) C NMR solid-state investigations describing a bilayer packing. It can be shown that the bilayer arrangement is the result of a kinetically driven crystallisation process, whereas the monolayer packing is the thermodynamically stable polymorph of the title compound. Powder spectra of dried self-assembled layers of N-(l-alkyl)-D-gluconamides showed only one-dimensional order and exhibited at most two periodicities. These could be assigned to a mono- and bilayer arrangement, respectively. Derivatives with long alkyl chains proved to have a smaller tendency towards monolayer assembling than homologues with a short tail.