Question

The term anomers of glucose refers to

• A. A mixture of (4)-glucose and (L)-glucose
• B. Enantiomers of glucose
• C. Isomers of glucose that differ in configuration at carbon one (C-1)
• D. Isomers of glucose that differ in configurations at carbons one and four (C-1 and C-4)

Answer 1

Answer: (C)

Isomers of glucose that differ in configuration at carbon one (C-1)

Answer 2

Due to cyclic hemiacetal or cyclic hemiketal structures, all the pentoses and hexoses exist in two stereoisomeric forms i.e., a form in which the OH at C1 in aldoese and C2 in ketoses lies towards the right and b form in which it lies towards left. Thus glucose, fructose, ribose etc, all exist in a and b form. Glucose exists in to forms a -D-glucose and

b -D glucose.

a -D-(+) equilibrium mixture b -(4)

glucose (+) glucose

As a result of cyclization of anomeric (C – 1) becomes asymmetric and the newly formed – OH group may be either on left or on right in Fischer projection thus resulting in the formation to two isomers (anomers). The isomers having – OH group ot the left of the C – 1 designated b -D glucose and the other having – OH group on the right as a -D-glucose.

and