Which of the following will give a positive Tollens' test? (12.4)


a. 1-propanol
b. 2-propanol
c. hexanal

Verified step by step guidance

1. Identify the functional group that gives a positive Tollens' test. Tollens' test is used to identify aldehydes.
2. Examine each compound to determine if it contains an aldehyde group.
3. 1-propanol is an alcohol, specifically a primary alcohol, and does not contain an aldehyde group.
4. 2-propanol is also an alcohol, specifically a secondary alcohol, and does not contain an aldehyde group.
5. Hexanal is an aldehyde, as indicated by the '-al' suffix, and will give a positive Tollens' test.

Key Concepts

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.

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 and capable of undergoing oxidation. In contrast, alcohols contain a hydroxyl group (–OH) and are generally less reactive in oxidation reactions, which is crucial for determining the outcome of the Tollens' test.

Oxidation and Reduction

Oxidation refers to the loss of electrons or an increase in oxidation state, while reduction is the gain of electrons or a decrease in oxidation state. In the context of the 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.