Question

Name the following monosaccharides by placing the appropriate terms

Answer 1

Concepts and reason

The concept used to solve this problem is to locate the anomeric carbon in the given structure and then name the compound using the configuration.

If the given monosaccharide, –OH group and $- {\rm{C}}{{\rm{H}}_2}{\rm{OH}}$ group are trans to each other, then it is called as $\alpha$ anomer. Similarly, if –OH group and $- {\rm{C}}{{\rm{H}}_2}{\rm{OH}}$ group are cis to each other, then it is called as $\beta$ anomer.

If the $- {\rm{C}}{{\rm{H}}_2}{\rm{OH}}$ group is drawn up, then it is known as D-sugar. If the $- {\rm{C}}{{\rm{H}}_2}{\rm{OH}}$ group is drawn down, then it is known as L-sugar.

Fundamentals

Anomers are the two structural forms of same molecule which differentiate from each other only in the direction of the OH (hydroxyl) group present at the hemiacetal carbon.

Six-membered ring containing an oxygen atom is known as pyranose ring. Similarly, the five-membered ring containing an oxygen atom is known as furanose ring.

The structure is as follows:

This is a six-membered ring, so it is a pyranose.

The structure is as follows:

This is a six-membered ring, so it is a pyranose.

The structure is as follows:

This is a five-membered ring, so it is a furanose.

Ans:

The name of the monosaccharide is $\beta {\rm{ - D - galactopyranose}}$ .

The name of the monosaccharide is $\beta {\rm{ - L - glucopyranose}}$ .

The name of the monosaccharide is $\beta {\rm{ - D - fructofuranose}}$ .