Textbook Question
Draw the structures of the products formed when the following compounds react with a reducing agent.
a.
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 43a
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 → ?
Verified step by step guidance1
Step 1: Understand the reaction type. Acetone (a ketone) reacts with ethanol (an alcohol) to form a hemiketal. A hemiketal is formed when a ketone reacts with one equivalent of an alcohol under acidic or basic conditions.
Step 2: Identify the functional groups involved. Acetone contains a carbonyl group (C=O), and ethanol contains a hydroxyl group (-OH). The reaction involves the nucleophilic attack of the alcohol's oxygen on the carbonyl carbon of the ketone.
Step 3: Draw the intermediate structure. The oxygen atom of ethanol attacks the carbonyl carbon of acetone, forming a tetrahedral intermediate. This intermediate has a hydroxyl group (-OH) and an ethoxy group (-OCH2CH3) attached to the same carbon.
Step 4: Write the structure of the hemiketal. The final structure of the hemiketal will have the central carbon bonded to: (1) a hydroxyl group (-OH), (2) an ethoxy group (-OCH2CH3), (3) a methyl group (-CH3), and (4) another methyl group (-CH3).
Step 5: Verify the reaction conditions. Ensure that the reaction is not proceeding further to form a full ketal, which would require an additional equivalent of ethanol and acidic conditions to replace the hydroxyl group with another ethoxy group.
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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 organic compounds formed when an alcohol reacts with an aldehyde or ketone, respectively. In this reaction, one molecule of alcohol adds to the carbonyl carbon, resulting in a structure that contains both an alcohol and an ether functional group. Hemiacetals and hemiketals are typically unstable and can further react to form acetals or ketals when a second alcohol molecule is added.
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Cyclic Hemiacetals Concept 1
Acetals and Ketals
Acetals and ketals are derived from hemiacetals and hemiketals through a condensation reaction with an alcohol, resulting in the loss of water. Acetals are formed from aldehydes, while ketals are formed from ketones. These compounds are more stable than their hemi counterparts and are characterized by having two alkoxy groups attached to the carbon that was originally part of the carbonyl group.
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2:17Formation of Hemiacetals and Acetals Concept 2
Hydrolysis of Acetals and Ketals
Hydrolysis of acetals and ketals involves the reaction of these compounds with water, leading to the regeneration of the original aldehyde or ketone and the alcohol. This reaction is typically catalyzed by an acid and is reversible. Understanding this process is crucial for predicting the products of reactions involving acetals and ketals, especially in the context of organic synthesis and reaction mechanisms.
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Related Practice
Textbook Question
The following names are incorrect. What is wrong with each?
b. 2-Butanal
Textbook Question
What two products result from the complete hydrolysis of this cyclic acetal?
Textbook Question
Which of the following compounds will react with Tollens' reagent? With Benedict's reagent?
a. Cyclopentanon
b. Hexanal
c.
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?
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.