Question

In addition to using numerical prefixes in the general names of sugars to indicate how many carbon atoms are present, we sometimes use the prefixes keto- and aldo- to indicate whether the sugar is a ketone or an aldehyde. For example, the monosaccharide fructose is often called a ketohexose to emphasize that it contains six carbons as well as the ketone functional group. For each of the monosaccharides, classify the sugars as aldohexoses, aldopentoses, ketohexoses, or ketopentoses.

Short answer

The aldohexoses, aldopentoses, ketohexoses, or ketopentoses are classified. Aldohexoses contain 6 carbons and an aldehyde functional group. Aldopentoses are classified by having 5 carbons and an aldehyde functional group present in the structure. Ketohexoses contain 6 carbons and a ketone functional group. Ketopentoses are classified by having 5 carbons and a ketone functional group present in the structure.

Step-by-step solution

To classify  aldohexoses, aldopentoses, ketohexoses, or ketopentoses.

To classify the important monosaccharides, we must first list them down.

There are monosaccharides listed under and they are D-ribose, D-arabinose, and D- ribulose.

There are also four monosaccharides listed under and they are D-glucose, D-mannose, D-galactose and D-fructose.

To classify aldohexoses

Then, to classify them, we must note that aldohexoses contain 6 carbons and an aldehyde functional group. Hence, the aldohexoses must come from the list of hexoses with six carbons.

Observe the structures given below, only D-fructose does not have an aldehyde functional group present in its structure. Thus, the only aldohexoses in the given list are D-mannose, D-glucose, and D-galactose.