Problem 93 - Chemistry: The Central Science

Question

Monosaccharides can be categorized in terms of the number of carbon atoms (pentoses have five carbons and hexoses have six carbons) and according to whether they contain an aldehyde (aldo- prefix, as in aldopentose) or ketone group (keto- prefix, as in ketopentose). Classify glucose and fructose in this way.

Step-by-Step Solution

Answer

Glucose and fructose are both composed of 6 carbon atoms, classifying them as hexoses. Glucose contains an aldehyde group, making it an aldohexose, while fructose contains a ketone group, classifying it as a ketohexose.

Step 1: 1. Determine the number of carbon atoms in glucose and fructose

Glucose and fructose are both composed of 6 carbon atoms, which can be confirmed by their molecular formulas (C6H12O6).

Step 2: 2. Identify the functional groups in glucose and fructose

To determine whether they contain an aldehyde or a ketone group, we need to examine their structures. - Glucose contains an aldehyde group (-CHO) as the highest-oxidized functional group. You can identify this by looking at the structure of glucose and noticing the presence of an aldehyde group at one end of the molecule. - Fructose contains a ketone group (>C=O) as the highest-oxidized functional group. You can identify this by looking at the structure of fructose and noticing the presence of a ketone group inside the molecule.

Step 3: 3. Classify glucose and fructose based on the results from steps 1 and 2

Based on the results from steps 1 and 2, the classifications for glucose and fructose are as follows: - Glucose: Since it has six carbon atoms and contains an aldehyde group, it is classified as an aldohexose. - Fructose: Since it has six carbon atoms and contains a ketone group, it is classified as a ketohexose.