Textbook Question
The carbonyl group can be reduced by addition of a hydride ion (H–) and (H+) a proton. Removal of H– and H+ from an alcohol results in a carbonyl group.
a. To which atom of the carbonyl is the hydride ion added and why?
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Ch.15 Aldehydes and Ketones
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 15, Problem 17
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 guidance1
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.
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Cyclic Hemiacetals Concept 1
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.
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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
Draw the structures of the hemiacetals or hemiketals formed in these reactions:
b.
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Textbook Question
The carbonyl group can be reduced by addition of a hydride ion (H–) and (H+) a proton. Removal of H– and H+ from an alcohol results in a carbonyl group.
b. In the reaction, indicate which direction represents reduction and which represents oxidation.
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Textbook Question
Determine whether the following compounds are acetals or ketals. Draw the structure of the aldehyde or ketone it came from.
c.
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Textbook Question
A fundamental difference between aldehydes and ketones is that one can be oxidized to carboxylic acids but the other cannot. Which is which? Give an example of a test to differentiate aldehydes from ketones.
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