Question

Treatment of either anomer of fructose with excess ethanol in the presence of a trace of HCI gives a mixture of the α and β anomers of ethyl-D-fructofuranoside. Draw the starting materials, reagents, and products for this reaction. Circle the aglycone in each product.

Short answer

An anomer is an epimer of a cyclic sugar which possess different configuration at the anomeric carbon. An epimer is one of a pair of stereoisomers which differs only at one stereocenter. For each set of anomers, there exists an alpha anomer and a beta anomer. Anomeric carbon is the hemiacetal or hemiketal carbon of that particular sugar. Fructose hasand-D-fructofuranose as anomers.

Step-by-step solution

Step-1.

An anomer is an epimer of a cyclic sugar which possess different configuration at the anomeric carbon. An epimer is one of a pair of stereoisomers which differs only at one stereocenter. For each set of anomers, there exists an alpha anomer and a beta anomer. Anomeric carbon is the hemiacetal or hemiketal carbon of that particular sugar. Fructose hasand-D-fructofuranose as anomers.

Step-2.

Treatment of either anomer of fructose with excess ethanol and trace of hydrochloric acid gives a mixture of and anomers of ethyl-D-fructofuranoside. Aglycone is the non-sugar part of the glycoside. Aglycone part is circled in both the products.