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

Cyclic Structures of Monosaccharides

GOB Chemistry

20. Carbohydrates

Cyclic Structures of Monosaccharides

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1:36 minutes

Problem 23a

Textbook Question

Identify the following carbohydrates as the ⍺ or β anomer:
(a)

Verified step by step guidance

Examine the structure of the carbohydrate provided in the image. Specifically, focus on the anomeric carbon, which is the carbon attached to two oxygen atoms: one in the ring and one in the hydroxyl (-OH) group.

Determine the orientation of the hydroxyl (-OH) group attached to the anomeric carbon. If the -OH group is pointing down (opposite to the CH2OH group on the last carbon of the ring), it is the α-anomer. If the -OH group is pointing up (same side as the CH2OH group), it is the ß-anomer.

Identify the CH2OH group on the last carbon of the ring (typically carbon 5 in a six-membered ring). This group helps establish the reference direction for determining the orientation of the -OH group on the anomeric carbon.

Compare the orientation of the -OH group on the anomeric carbon to the CH2OH group. Use the rules from step 2 to classify the carbohydrate as either the α or ß anomer.

Label the carbohydrate as either the α or ß anomer based on your observations. Ensure that you clearly document your reasoning for the classification.

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Key Concepts

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

Anomers

Anomers are a type of stereoisomer found in carbohydrates that differ in configuration at the anomeric carbon, which is the carbon derived from the carbonyl group during the formation of a cyclic structure. In the case of sugars, the anomeric carbon is typically the first carbon in the ring. Anomers are classified as either alpha (α) or beta (β) based on the orientation of the hydroxyl group attached to the anomeric carbon relative to the CH2OH group on the last carbon in the chain.

Cyclic Structure of Carbohydrates

Carbohydrates can exist in linear or cyclic forms, with the cyclic form being more stable in aqueous solutions. The formation of a cyclic structure occurs through a reaction between the carbonyl group and a hydroxyl group, resulting in a hemiacetal or acetal. This process leads to the creation of a ring structure, which is crucial for determining the anomeric configuration of the carbohydrate.

D- and L- Configuration

The D- and L- configuration of carbohydrates refers to the orientation of the hydroxyl group on the penultimate carbon (the second-to-last carbon) in the linear form of the sugar. If the hydroxyl group is on the right side in the Fischer projection, the sugar is classified as D; if it is on the left, it is classified as L. This configuration is important for identifying the specific anomer of a carbohydrate, as it influences the overall structure and properties of the molecule.

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