What are the differences in the Fischer projections of d-fructose and d-galactose?

Verified step by step guidance

1. Understand the Fischer projection: A Fischer projection is a two-dimensional representation of a molecule's three-dimensional structure, commonly used for carbohydrates. The vertical lines represent bonds going into the plane (away from the viewer), and the horizontal lines represent bonds coming out of the plane (toward the viewer). The most oxidized carbon is placed at the top.
2. Identify the structure of D-fructose: D-fructose is a ketohexose, meaning it has six carbons and a ketone functional group. In its Fischer projection, the ketone group is located at the second carbon (C2), and the hydroxyl (-OH) groups on the remaining carbons are arranged in a specific pattern.
3. Identify the structure of D-galactose: D-galactose is an aldohexose, meaning it has six carbons and an aldehyde functional group. In its Fischer projection, the aldehyde group is located at the first carbon (C1), and the hydroxyl (-OH) groups on the remaining carbons are arranged in a specific pattern.
4. Compare the functional groups: The key difference between D-fructose and D-galactose is the type and position of the carbonyl group. D-fructose has a ketone group at C2, while D-galactose has an aldehyde group at C1.
5. Compare the hydroxyl group arrangements: The arrangement of the hydroxyl (-OH) groups on the chiral carbons (C3, C4, and C5) differs between D-fructose and D-galactose. Carefully examine the Fischer projections to identify the specific differences in the orientation of these groups.

Key Concepts

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting the stereochemistry of carbohydrates. In these projections, vertical lines represent bonds that extend away from the viewer, while horizontal lines indicate bonds that come towards the viewer. This format helps in visualizing the spatial arrangement of atoms and functional groups in sugars.

D-Fructose Structure

D-fructose is a ketohexose, meaning it contains six carbon atoms and a ketone functional group. In its Fischer projection, the carbonyl group is located at the second carbon atom, and it has a specific arrangement of hydroxyl groups that distinguishes it from other sugars. Understanding its structure is crucial for comparing it with other carbohydrates, such as D-galactose.

D-Galactose Structure

D-galactose is an aldohexose, which means it has six carbon atoms and an aldehyde functional group. In its Fischer projection, the carbonyl group is at the first carbon atom, and the arrangement of hydroxyl groups differs from that of D-fructose. Recognizing these structural differences is essential for understanding the distinct properties and functions of these two sugars.