Epimers:Sugar which are differ from each other only in the configuration around one carbon atom are called Epimer.

Mannose and glucose are epimers at C2, galactose and glucose are epimers at C4

Epimers : – stereoisomers that differ only in configuration about one chiral center.

Mutarotation:Aldo hexose when dissolved in water the optical rotation gradually changed until constant rotation of sugar is reached this is called mutarotation.

Cyclic structure of monosaccharide

• all monosaccharide have a cyclic hemiacetal structure. It is (the intra molecular reaction of hydroxyl group in carbon 5 with the carbonyl group forming a cyclic hemiacetal with a 6 member ring containing one oxygen and 5 carbon atom) this is called (( Hawarth Formula )).

• The hawarth formula at D(+) glucose can exist as two isomers because a new cheril center is created at carbon no. 1 to form a cyclic hemiacetal, the new cheril carbon is called ( anomeric carbon ) as result there are two isomers of D glucose, α D glucose and B D- glucose.

α-D-glucose in which the hydroxyl group at the anomeric carbon is below the place of the ring while in β-D glucose the anomeric carbon is above the place of the ring.Hemiacetal formation also occur with D- mannose, D- galactose form 6 member ring like glucose.While D-fructose is found as 5 member ring hemiketal.Monosaccharide exist in two cyclic form

Pyranose (6member ring)Aldohexose

Furanose (5 member ring)Ketohexose

Pyranose, furanose, respectively hawarth structural formula

• α and β form of glucose are formed by hemiacetalization. Formation of hemiacetyl is a condensation reaction between aldo group at C1 and OH group at C5 at the same compound forming ring structure.

• Glycogen is synthesized from α D glucopyranose whereas cellulose is synthesized from β-D glucopyranose.

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