Question

34.) The configuration at which carbon atom determines if a monosaccharide is D or L? A) The lowest numbered chiral carbon B) The highest numbered chiral carbon C) The chiral carbon closest to the aldehyde or keto group D) The carbon of the primary alcohol group

Answer 1

B) the highest numbered chiral Carbon is correct option.

Explanation:

to determine the configuration of acyclic monosaccharide if it is D or L , we shall first do numbering.

Then , we look at the -OH group which is attached to the last stereocenters (highest numbered) monosaccharide,

If -OH group is at left side ,then it will be termed as L configuration.

if -OH group at last stereocenter is at right side then it will be termed as D configuration.

Let us take example of two monosaccharide ICH₂OH ICHO HO2H HO. 3 H 5CH₂OH A L-configuration HO. 3 H H 4 COH Hest fou 6 CH₂OH 6 D-conth In Structure A, The left side of the centre, therefore it –OH group is at the highest number stereo- is termed as L-configuration While in structure B, the -OH group is at the right side of the highest number stercocentre, Hence, It is termed as b-configuration
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