What sugar is the C-3 epimer of D-fructose?

Verified step by step guidance

1. Understand the concept of epimers: Epimers are stereoisomers that differ in configuration at only one specific carbon atom, while the rest of the molecule remains identical. In this case, we are looking for the C-3 epimer of D-fructose.
2. Recall the structure of D-fructose: D-fructose is a ketohexose, meaning it has six carbons and a ketone functional group at the C-2 position. Its Fischer projection shows the hydroxyl (-OH) groups on specific carbons (C-3, C-4, and C-5) in a particular arrangement.
3. Identify the C-3 position: In the Fischer projection of D-fructose, the C-3 carbon is the third carbon from the top, and its hydroxyl group is on the left side of the projection.
4. Generate the C-3 epimer: To create the C-3 epimer, invert the configuration of the hydroxyl group at the C-3 position. If the hydroxyl group is on the left in D-fructose, place it on the right for the epimer, while keeping the rest of the molecule unchanged.
5. Name the resulting sugar: After modifying the C-3 position, determine the name of the new sugar by comparing its structure to known ketohexoses. This will give you the name of the C-3 epimer of D-fructose.

Key Concepts

Epimers

Epimers are a specific type of diastereomer that differ in configuration at only one stereogenic center. In the context of sugars, this means that two sugars can have the same molecular formula and differ only at one carbon atom's stereochemistry. Understanding epimers is crucial for identifying relationships between different sugars, such as d-fructose and its epimers.

D-Fructose Structure

D-fructose is a ketohexose sugar, meaning it contains six carbon atoms and a ketone functional group. Its structure includes a carbonyl group at C-2 and hydroxyl groups at the other carbons. Recognizing the structure of d-fructose is essential for determining its epimers, particularly by identifying the stereochemistry at C-3.

Sugar Nomenclature

Sugar nomenclature involves the systematic naming of carbohydrates based on their structure and stereochemistry. The prefixes 'D-' and 'L-' indicate the configuration of the sugar relative to glyceraldehyde, while terms like 'epimer' specify the type of stereochemical difference. Familiarity with this nomenclature is important for accurately identifying and discussing sugars and their relationships.