Reduction of D-fructose with a reducing agent yields a mixture of D-sorbitol along with a second, isomeric product. What is the structure of the second product?

Verified step by step guidance

1. Understand the context: Reduction of D-fructose involves the addition of hydrogen (H₂) to the carbonyl group (C=O) in the sugar molecule, converting it into an alcohol group (-OH). This process is typically carried out using a reducing agent such as sodium borohydride (NaBH₄) or hydrogen gas with a catalyst.
2. Identify the structure of D-fructose: D-fructose is a ketohexose, meaning it contains six carbons and a ketone group at the second carbon (C2). The ketone group is the functional group that will be reduced.
3. Determine the products of reduction: Reduction of the ketone group in D-fructose can yield two different products because the ketone group is located at C2, which is adjacent to a chiral center (C3). Reduction can produce either D-sorbitol (a sugar alcohol derived from D-glucose) or another isomeric sugar alcohol.
4. Explain the formation of the second product: The second product is D-mannitol, which forms when the reduction of the ketone group leads to the formation of a hydroxyl group (-OH) with the opposite stereochemistry at C2 compared to D-sorbitol. This occurs because the reduction process can produce a racemic mixture at the C2 position.
5. Summarize the structures: The two products of the reduction of D-fructose are D-sorbitol (with the same stereochemistry as D-glucose) and D-mannitol (with the stereochemistry of D-mannose). Both are sugar alcohols, differing only in the configuration of the hydroxyl group at C2.

Key Concepts

Reduction of Sugars

Reduction of sugars involves the conversion of carbonyl groups (aldehydes or ketones) into alcohols using reducing agents. In the case of d-fructose, a ketose sugar, reduction leads to the formation of d-sorbitol, an alditol. Understanding this process is crucial for predicting the products of sugar reduction.

Isomerism

Isomerism refers to the existence of compounds with the same molecular formula but different structural arrangements or spatial orientations. In the context of d-fructose reduction, the second product formed alongside d-sorbitol is likely to be an isomer, such as d-mannitol, which has a different configuration at one or more carbon atoms.

Structural Representation of Sugars

Structural representation of sugars involves depicting their molecular structure, including the arrangement of atoms and functional groups. For d-fructose and its reduction products, understanding how to draw and interpret Fischer projections or Haworth structures is essential for identifying the second product's structure and its relationship to d-sorbitol.