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

15. Aldehydes and Ketones

Hemiacetal and Acetal Formation

GOB Chemistry

15. Aldehydes and Ketones

Hemiacetal and Acetal Formation

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Problem 14c

Textbook Question

Determine whether the following compounds are acetals or ketals. Draw the structure of the aldehyde or ketone it came from.
c.

Verified step by step guidance

Step 1: Understand the definitions of acetals and ketals. Acetals are formed when an aldehyde reacts with two alcohol molecules, while ketals are formed when a ketone reacts with two alcohol molecules. Both involve the replacement of the carbonyl group with two -OR groups.

Step 2: Examine the structure of the compound provided in the image. Identify the central carbon atom bonded to two -OR groups (alkoxy groups). This is the key feature of acetals and ketals.

Step 3: Determine whether the original compound was derived from an aldehyde or a ketone. If the central carbon atom was originally part of a carbonyl group (C=O) with one hydrogen atom attached, it came from an aldehyde. If it was part of a carbonyl group with two carbon groups attached, it came from a ketone.

Step 4: Draw the structure of the aldehyde or ketone that the compound originated from. To do this, replace the two -OR groups with a single oxygen atom double-bonded to the central carbon atom.

Step 5: Label the compound as either an acetal or a ketal based on whether the original molecule was an aldehyde or a ketone. Acetals come from aldehydes, and ketals come from ketones.

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Key Concepts

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

Acetals and Ketals

Acetals and ketals are types of organic compounds formed from the reaction of aldehydes or ketones with alcohols. Acetals are derived from aldehydes, while ketals come from ketones. Both structures feature a carbon atom bonded to two alkoxy groups (–O–R) and a hydrogen atom (in acetals) or another carbon atom (in ketals). Understanding the distinction between these two types of compounds is crucial for identifying their structures.

Aldehydes and Ketones

Aldehydes and ketones are carbonyl-containing compounds characterized by the presence of a carbonyl group (C=O). Aldehydes have the carbonyl group at the end of the carbon chain, while ketones have it within the chain. Recognizing the structure of these compounds is essential for determining the corresponding acetal or ketal, as the type of carbonyl compound dictates the product formed during the reaction with alcohol.

Reaction Mechanism

The formation of acetals and ketals involves a nucleophilic addition reaction where the carbonyl carbon is attacked by an alcohol. This reaction typically proceeds through a hemiacetal or hemiketal intermediate before yielding the final acetal or ketal product. Understanding this mechanism is important for predicting the structures of the original aldehyde or ketone and the resulting acetal or ketal, as well as for grasping the conditions under which these reactions occur.

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Related Practice

Textbook Question

Acetals and ketals are usually made by reaction of an aldehyde or ketone with two molecules of a monoalcohol. If an aldehyde or ketone reacts with one molecule of a dialcohol, however, a cyclic acetal or ketal results.

b. Draw the cyclic ketal formed when the hemiketal from part (a) reacts with the ―OH labeled in blue.

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Multiple Choice

What would be the product of the following reaction?

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Multiple Choice

Draw the intermediate in the following reaction.

1018

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Multiple Choice

Draw the structure of the product when one mole of cyclopentanone reacts with two moles of methanol in an acidic solution.

Draw the structures of the hemiacetals or hemiketals formed in these reactions:

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Textbook Question

Cyclic hemiacetals commonly form if a molecule has both an alcohol group and a carbonyl group elsewhere in the same molecule, especially if they are four or five carbons apart. What is the structure of the hydroxy aldehyde from which this hemiacetal might form?

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Textbook Question

In Problem 15.24, you were given the structure of the free aldehyde form of glucose. Try to draw the two cyclic hemiacetal forms of glucose you would get if (a) the OH on C4 formed the ring and (b) the OH on C3 formed the ring.

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Textbook Question

For each compound shown next, determine whether it is a hemiacetal, a hemiketal, an acetal, or a ketal.

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