Amylose V complexes. II. Lower molecular weight ketones

Abstract

The acetone‐ and methyl ethyl ketone‐amylose V complexes have been prepared and their unit cell dimensions calculated from their x‐ray powder patterns. This work demonstrates the size‐determining effect of these two ketones on the amylose V complex. The small unit cell, with a helix diameter of 13.0 A., observed with the wet methanol and ethanol complexes, is not found with the acetone and methyl ethyl ketone complexes. The wet ketone‐amylose V complexes and the thoroughly dried ketone complexes have the larger helix diameter of 13.7 A. This is the first report of an anhydrous amylose V complex with the expanded helix diameter. Thorough extraction of the methyl ethyl ketone‐amylose complex with methyl alcohol did not change the 13.7 A. helix diameter, although methyl alcohol‐extracted acetone‐amylose complex resulted in a mixture of the 13.0 A. and 13.7 A. helix diameter types. This work demonstrates the size effect of the lower molecular weight ketones on the amylose crystalline structure.

Amylose V complexes from dimethyl sulfoxide solutions

“…The part that various polar solvents play in determining the diameter of the amylose helices has been the subject of some recent i n v e s t i g a t i~n .~~ Germino et al 4 reported the existence on anhydrous amylose V complexes of acetone and methyl ethyl ketone with a 13.7 A. helix diameter. They also found that water had very little effect on these complexes, since the x-ray diffraction pattern was unchanged for samples having water : glucose mole ratios varying from 12 : 1 to 0.65 : 1.…”