Question

8 Which of the above disaccharides will undergo oxidation?

Answer 1

	Monosaccharides	Type of glycosidic bond	Name of disaccharide
4	Glucose-Glucose	α 1→4	Maltose or 1-4'-α-D-glucopyranosyl-D-glucopyranose
5	Galactose-Glucose	β 1→4	Lactose or 1-4'-β-D-galactopyranosyl-D-glucopyranose
6	Glucose-Fructose	α 1→ 2 β	Sucrose or α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside
7	Glucose-Glucose	β 1→4	Cellobiose or 1-4'-β -D-glucopyranosyl-D-glucopyranose

8. The ones that can undergo oxidations are those with a free anomeric carbon, which are all of them except sucrose, in which the two monosaccharides are bonded through their anomeric carbons, so they none of the can adopt the required linear structure to be oxidized. The other three molecules have one monosaccharide unit (the one on the right of each structure) which has a free anomeric carbon, which can consequently react by, for example, being oxidized.