Textbook Question
Which of the following will give a positive Tollens' test?
a. propanal
b. ethanol
c. ethyl methyl ether
Ch.12 Alcohols, Thiols, Ethers, Aldehydes, and Ketones
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353
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Table of contents
- Ch.1 Chemistry in Our Lives11
- Ch.2 Chemistry and Measurements80
- Ch.3 Matter and Energy54
- Ch.4 Atoms and Elements51
- Ch.5 Nuclear Chemistry42
- Ch.6 Ionic and Molecular Compounds57
- Ch.7 Chemical Quantities and Reactions41
- Ch.8 Gases29
- Ch.9 Solutions51
- Ch.10 Acids and Bases and Equilibrium65
- Ch.11 Introduction to Organic Chemistry: Hydrocarbons78
- Ch.12 Alcohols, Thiols, Ethers, Aldehydes, and Ketones83
- Ch.13 Carbohydrates54
- Ch.14 Carboxylic Acids, Esters, Amines, and Amides90
- Ch.15 Lipids61
- Ch.16 Amino Acids, Proteins, and Enzymes84
- Ch.17 Nucleic Acids and Protein Synthesis83
- Ch.18 Metabolic Pathways and ATP Production67
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
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Timberlake 13th EditionCh.12 Alcohols, Thiols, Ethers, Aldehydes, and KetonesProblem 42
Timberlake 13th EditionCh.12 Alcohols, Thiols, Ethers, Aldehydes, and KetonesProblem 42Chapter 12, Problem 42
Which of the following will give a positive Tollens' test?
a. 1-propanol
b. 2-propanol
c. hexanal
Verified step by step guidance1
Understand the Tollens' test: The Tollens' test is a chemical test used to identify aldehydes. It involves the use of Tollens' reagent, which contains silver ions (Ag⁺) in an ammonia solution. Aldehydes are oxidized to carboxylic acids, and the silver ions are reduced to metallic silver, forming a characteristic silver mirror on the test tube.
Analyze the given compounds: a. 1-propanol is a primary alcohol, b. 2-propanol is a secondary alcohol, and c. hexanal is an aldehyde. Recall that the Tollens' test specifically reacts with aldehydes, not alcohols.
Determine the functional group of each compound: Alcohols (1-propanol and 2-propanol) do not have the carbonyl group (C=O) characteristic of aldehydes, so they will not react with Tollens' reagent. Hexanal, on the other hand, contains an aldehyde group (R-CHO), which can be oxidized by Tollens' reagent.
Predict the outcome of the test: Since hexanal is an aldehyde, it will give a positive Tollens' test, resulting in the formation of a silver mirror. The other two compounds, 1-propanol and 2-propanol, will not react and will give a negative Tollens' test.
Conclude: The compound that will give a positive Tollens' test is hexanal (option c).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Tollens' Test
Tollens' test is a qualitative test used to identify aldehydes and certain reducing sugars. It involves the use of Tollens' reagent, which contains silver nitrate in ammonia, that oxidizes aldehydes to carboxylic acids while reducing silver ions to metallic silver. A positive result is indicated by the formation of a silver mirror on the test container.
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Tollens' Test Concept 2
Aldehydes vs. Alcohols
Aldehydes are organic compounds characterized by the presence of a carbonyl group (C=O) at the end of the carbon chain, making them reactive in oxidation reactions. In contrast, alcohols contain a hydroxyl group (–OH) and are generally less reactive towards oxidation, particularly secondary and tertiary alcohols, which do not yield a positive Tollens' test.
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0:34Naming Aldehydes Example 2
Oxidation and Reduction
Oxidation refers to the loss of electrons or an increase in oxidation state, while reduction involves the gain of electrons or a decrease in oxidation state. In the context of Tollens' test, aldehydes are oxidized to carboxylic acids, and the silver ions in Tollens' reagent are reduced to metallic silver, demonstrating the redox nature of the reaction.
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0:55Reduction of Monosaccharides Example 1
Related Practice
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