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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1:54 minutes

Problem 17

Textbook Question

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

Verified step by step guidance

Step 1: Understand the definitions of the terms. A hemiacetal contains one -OH group and one -OR group attached to the same carbon atom, which is also bonded to a hydrogen atom. A hemiketal is similar but the central carbon is bonded to two alkyl groups instead of a hydrogen. An acetal contains two -OR groups attached to the same carbon atom, which is also bonded to a hydrogen atom. A ketal is similar to an acetal but the central carbon is bonded to two alkyl groups instead of a hydrogen.

Step 2: Examine the structure of compound (a). Look for the functional groups attached to the central carbon atom. Identify whether the central carbon is bonded to a hydrogen atom or two alkyl groups, and whether it has one or two -OR groups.

Step 3: Repeat the process for compound (b). Carefully analyze the functional groups attached to the central carbon atom and determine whether it fits the definition of a hemiacetal, hemiketal, acetal, or ketal.

Step 4: Analyze compound (c) in the same way. Pay attention to the number and type of groups attached to the central carbon atom, and compare them to the definitions provided in Step 1.

Step 5: Finally, evaluate compound (d). Use the same approach to identify the functional groups and classify the compound as a hemiacetal, hemiketal, acetal, or ketal based on the structural features.

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Key Concepts

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

Hemiacetals and Hemiketals

Hemiacetals and hemiketals are formed when an alcohol reacts with an aldehyde or a ketone, respectively. A hemiacetal contains one -OH group and one -OR group attached to the same carbon, while a hemiketal has two -OR groups. These compounds are typically unstable and can further react to form acetals or ketals.

Acetals and Ketals

Acetals and ketals are derived from hemiacetals and hemiketals through a reaction with an alcohol, resulting in the replacement of the -OH group with another -OR group. Acetals have two -OR groups attached to the carbon that was originally part of the aldehyde, while ketals have two -OR groups attached to the carbon from the ketone. These compounds are generally more stable than their hemi counterparts.

Structural Identification

To determine whether a compound is a hemiacetal, hemiketal, acetal, or ketal, one must analyze its structure. This involves identifying the functional groups present, such as -OH and -OR, and the carbon's connectivity to determine if it originated from an aldehyde or ketone. Understanding the structural features is crucial for accurate classification.

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Related Practice

Textbook Question

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

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Textbook Question

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

628

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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

Glucose is the major sugar in mammalian blood. We often see it represented as either the "free aldehyde" or the cyclic hemiacetal forms shown here. Of the two forms of glucose, the cyclic hemiacetal is the preferred form found in blood. Can you suggest two reasons why?

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Textbook Question

Write the structures of the hemiacetal or hemiketal that result from reactions (a) and (b). Write the structures of the complete hydrolysis products of the acetal or ketal in (c) and (d).

a. Acetone + Ethanol → ?

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Textbook Question

What two products result from the complete hydrolysis of this cyclic acetal?

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

Key Concepts

Hemiacetals and Hemiketals

Acetals and Ketals

Structural Identification

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