20. Carbohydrates

Identify each pair of carbohydrates as enantiomers or diastereomers.

Draw the enantiomer of given structure of Xylose, and identify as D or L.

Aldoheptoses have five chiral carbon atoms. What is the maximum possible number of aldoheptose stereoisomers? Draw all of the aldoheptose stereoisomers.

Only three stereoisomers are possible for 2,3-dibromo-2, 3-dichlorobutane. Draw them, indicating which pair are enantiomers (optical isomers). Why does the other isomer not have an enantiomer?

Sucrose and d-glucose rotate plane-polarized light to the right; d-fructose rotates light to the left. When sucrose is hydrolyzed, the glucose–fructose mixture rotates light to the left.

b. Why do you think the mixture is called “invert sugar”?

 Identify each of the following pairs of Fischer projections as enantiomers or identical compounds:

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