engleski

Crystal polymorphism in several saccharides

Scanning electron microscopy micrographs were recorded with JEOL T300 instrument operating at 10 kV. All samples were carbon coated. Raman spectra from 10 - 300 cm-1 were recorded with DILOR Z24 Raman spectrometer. Samples were cooled with CTI CRYOGENICS closed cycle Helium cryostat. Chemicals were products of Sigma Aldrich, purity 98 % or better. Dihidroxyacetone (2, 5-dihydroxymethyl-2, 5-dihydroxy-1, 4-dioxane) exhibits the most complex behaviour, having 5 crystal modifications. In the SEM photograph small dark spots present may indicate the pores through which water evaporated in the electron beam. In the low frequency Raman spectra the same number of phonons is expec-ted to be observed for dioxane and for glyceraldehyde - six. We can com- pare the phonons positions of glycolal- dehyde with those of dioxane, and as- sign the OH torsion to the 240 cm-1 band.

electron microscopy; Raman spectroscopy; glyceraldehyde; glycolaldehyde; dihydroxyacetone

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