Keto-Enol Tautomerism and Sugar Interconversion

This page discusses the Keto-Enol-Tautomerie of fructose and glucose, focusing on their structural changes in different pH environments. The content covers the following key points:

1. Fructose Structure: The page begins with a structural representation of fructose in its β-D-fructopyranose form.

2. Alkaline Environment Conversion: In alkaline solutions, fructose undergoes a transformation into glucose. This process is illustrated with structural diagrams showing the conversion steps.

3. Optical Activity: The document explains that optical activity is a prerequisite for chirality in molecules like fructose, which lacks a mirror plane.

4. Glucose Structure: The glucose structure is presented in its open-chain and cyclic forms, demonstrating the equilibrium between these states.

5. Fehling's Test Limitations: The text points out that the Fehling test is not suitable for distinguishing between glucose and fructose in alkaline conditions due to their interconversion.

6. Acidic Environment Stability: In acidic media, keto-enol tautomerism does not occur, and the sugars remain stable in their original forms.

7. Hemiacetal and Acetal Structures: The page concludes with a brief mention of hemiacetal and acetal structures, which are relevant to sugar chemistry.

Vocabulary: Keto-Enol-Tautomerie refers to a chemical equilibrium between a ketone or aldehyde (keto form) and an enol structure.

Example: The conversion of fructose to glucose in alkaline solution is an example of keto-enol tautomerism.

Definition: Optical activity is the ability of a chiral molecule to rotate the plane of polarized light, which is a characteristic of molecules with asymmetric carbon atoms.

Highlight: The Fehling test's inability to distinguish between glucose and fructose in alkaline conditions due to their interconversion is a crucial point for understanding sugar chemistry.

Quote: "Im sauren Milieu findet keine Keto-Enol-Tautomerie statt." (In acidic media, no keto-enol tautomerism takes place.)