Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

20. Carbohydrates

Mutarotation

GOB Chemistry

20. Carbohydrates

Mutarotation

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3:00 minutes

Problem 73

Textbook Question

If α−galactose is dissolved in water, β−galactose is eventually present. Explain how this occurs.

Verified step by step guidance

Understand that α-galactose and β-galactose are anomers, which are a type of stereoisomers differing in the configuration around the anomeric carbon (the carbon derived from the carbonyl group in the cyclic form of the sugar).

Recognize that when α-galactose is dissolved in water, it undergoes a process called mutarotation. Mutarotation is the interconversion between the α and β forms of a sugar through the open-chain form.

In water, the cyclic form of α-galactose can briefly open up to form its linear (open-chain) structure. This occurs because the glycosidic bond at the anomeric carbon is not fixed and can break in aqueous solution.

Once in the open-chain form, the molecule can reclose to form either the α or β anomer. The β form is created when the hydroxyl group on the anomeric carbon is positioned on the opposite side of the ring compared to the α form.

Over time, an equilibrium is established between the α and β forms of galactose in solution, with both forms present in specific proportions. This is why β-galactose is eventually present when α-galactose is dissolved in water.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Anomeric Carbon

The anomeric carbon is the carbon atom in a sugar molecule that is derived from the carbonyl carbon during the formation of a cyclic structure. In the case of galactose, this carbon can exist in two configurations: α and β. The interconversion between these forms is crucial for understanding how α-galactose can eventually lead to the presence of β-galactose in solution.

Mutarotation

Mutarotation is the process by which anomeric forms of sugars interconvert in solution, resulting in a change in optical rotation. When α-galactose is dissolved in water, it undergoes mutarotation, allowing it to convert to β-galactose. This dynamic equilibrium between the anomers is a key concept in carbohydrate chemistry.

Equilibrium in Solution

In a solution, chemical species can exist in dynamic equilibrium, where the rates of the forward and reverse reactions are equal. For α- and β-galactose, this means that while α-galactose can convert to β-galactose, the reverse reaction can also occur. Eventually, a stable ratio of both anomers is established, explaining the presence of β-galactose when α-galactose is dissolved in water.

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