Question

Why does the Tollens' test produce solid silver with aldehydes and not with ketones? A. Ketones are more sterically hindered than aldehydes. B. Aldehydes can be oxidized to the carboxylic acid, while ketone cannot. C. Ketones do not have an acidic proton while aldehydes do have one. D. Aldehydes are more sterically hindered than ketones.

Short answer

B. Aldehydes can be oxidized to the carboxylic acid, while ketones cannot.

Step-by-step solution

Understand the Tollens' Test

The Tollens' test is used to identify aldehydes. It involves the reduction of silver ions (Ag+) to metallic silver (Ag) and the oxidation of an aldehyde to a carboxylic acid.

Identify the Oxidation Process

Aldehydes can be easily oxidized to carboxylic acids, while ketones cannot be oxidized as readily. This is because the presence of the hydrogen atom in the aldehyde functional group allows for oxidation, whereas ketones lack this hydrogen.

Analyze the Multiple-Choice Options

Option B states that aldehydes can be oxidized to the carboxylic acid, while ketones cannot. This option correctly aligns with the knowledge that aldehydes react in Tollens' test due to their oxidation capability.

Select the Correct Answer

From the given options, the correct choice is B: Aldehydes can be oxidized to the carboxylic acid, while ketones cannot.

Key concepts

Aldehyde Oxidation

Aldehyde oxidation is a key chemical reaction in organic chemistry. Aldehydes are organic compounds containing a carbonyl group (C=O) bonded to at least one hydrogen atom. This unique structure allows aldehydes to undergo oxidation.
Oxidizing agents, like the Tollens' reagent, can convert aldehydes into carboxylic acids. Tollens' reagent is a solution containing silver ions (Ag+) in ammonia (NH3). When an aldehyde is present, it donates electrons to the silver ions, reducing them to metallic silver (Ag). Simultaneously, the aldehyde itself is oxidized to a carboxylic acid.
This process does not occur with ketones because they lack the hydrogen atom necessary for this oxidation reaction. As a result, ketones cannot be oxidized to carboxylic acids under these conditions.

Functional Groups

Functional groups are specific groups of atoms within molecules that determine the chemical properties of those molecules. In the context of aldehydes and ketones:

• Aldehydes possess a carbonyl group (C=O) bonded to at least one hydrogen atom. This makes them reactive to oxidation agents like Tollens' reagent.
• Ketones have a carbonyl group (C=O) bonded to two carbon atoms. This structure lacks the hydrogen atom necessary for the reaction with Tollens' reagent.

Understanding the differences in functional groups helps chemists predict and explain the reactivity of different organic compounds. The presence or absence of specific atoms or groups of atoms within these structures dictates how the molecules will behave in various chemical reactions.

Organic Chemistry Reactions

Organic chemistry reactions involve the breaking and forming of bonds between carbon atoms and other elements. Here are a few general types of reactions:

• Addition reactions: Atoms are added to unsaturated molecules (like alkenes and alkynes) without removing any other atoms. These reactions often involve double or triple bonds.
• Substitution reactions: One atom or group of atoms in a molecule is replaced by another atom or group of atoms. For example, in halogenation, a hydrogen atom may be replaced by a halogen atom.
• Oxidation-reduction reactions: Electrons are transferred between atoms or molecules. Oxidation involves the loss of electrons, while reduction involves the gain of electrons.

The Tollens' test is an example of an oxidation-reduction reaction where the aldehyde is oxidized to a carboxylic acid, and silver ions are reduced to metallic silver.
Each reaction type provides valuable insights into the behavior and transformation of organic compounds, making it essential to grasp their fundamental principles for advanced studies and applications in chemistry.