Problem 23 - A Complete Resource Book in Chemistry for JEE Main

Question

Ketones \(\left(\mathrm{R}_{1} \mathrm{COR}_{2}\right) ; \mathrm{R}_{1}=\mathrm{R}_{2}=\) alkyl group, can be obtained in one step by (a) hydrolysis of esters (b) oxidation of primary alcohols (c) oxidation of secondary alcohols (c) reaction of acid halides and alcohlos

Step-by-Step Solution

Answer

The correct method is (c) oxidation of secondary alcohols.

Step 1: Understanding the Question

The exercise asks for a method to synthesize ketones specifically when both R groups are alkyl groups, through a one-step process. We must analyze each given option to determine which one directly results in the formation of ketones.

Step 2: Analyzing Option (a): Hydrolysis of Esters

Hydrolysis of esters typically results in the formation of carboxylic acids or alcohols, not ketones. Therefore, this option does not provide a one-step synthesis of ketones.

Step 3: Examining Option (b): Oxidation of Primary Alcohols

The oxidation of primary alcohols usually leads to the formation of aldehydes or carboxylic acids. Since ketones are not directly formed from primary alcohols, this option is not valid for one-step ketone synthesis.

Step 4: Checking Option (c): Oxidation of Secondary Alcohols

Oxidation of secondary alcohols directly leads to the formation of ketones. For example, oxidizing isopropanol gives acetone, which is a ketone. Thus, this is a valid one-step method to synthesize ketones when both R groups are alkyl.

Step 5: Reviewing Option (d): Reaction of Acid Halides and Alcohols

The reaction of acid halides and alcohols typically leads to the formation of esters, not ketones. Therefore, this option does not directly form ketones in one step.

Step 6: Conclusion

After evaluating all options, the correct method for one-step synthesis of ketones, with both R groups as alkyl groups, is the oxidation of secondary alcohols.

Key Concepts

Ketone Synthesis

Ketones are an important class of organic compounds characterized by a carbonyl group (C=O) flanked by two alkyl groups. These compounds find applications in various fields, including pharmaceuticals and industrial chemistry. Synthesizing ketones efficiently is vital for producing these valuable compounds. Among the methods for ketone synthesis, oxidation of secondary alcohols is a straightforward one-step process that transforms alcohols directly into ketones.

• Ketone structure: Contain a carbonyl group bonded to two alkyl groups.
• Applications: Used in synthesis of various organic compounds.
• Synthesis challenge: Creating ketones with minimal steps is crucial for efficient production.

Understanding the most efficient methods of ketone synthesis helps in designing reactions for industrial and laboratory settings. The oxidation of secondary alcohols provides a direct way to produce ketones, which is favored due to its simplicity and effectiveness.

Oxidation of Secondary Alcohols

A secondary alcohol is a molecule where the hydroxyl (OH) group is attached to a secondary carbon atom, which in turn is bonded to two other carbon atoms. Oxidizing secondary alcohols is a direct method to produce ketones, as it involves the removal of hydrogen atoms and the formation of a carbonyl group.

• Reaction process: The alcohol's hydroxyl group is oxidized, removing hydrogen atoms.
• Common oxidizing agents: These catalysts include pyridinium chlorochromate (PCC) and chromic acid (H₂CrO₄).
• Result: The oxidation results in the conversion of the alcohol to a ketone with the carbonyl group replacing the hydroxyl group.

For example, when isopropanol (a secondary alcohol) is oxidized, it yields acetone, which is a ketone.
The efficiency of this method makes it a favored choice in both industrial and laboratory settings to obtain ketones from simple alcohol precursors.

Functional Group Transformation

Functional group transformation plays a pivotal role in organic chemistry, enabling the conversion of one functional group to another. This is fundamental in the synthesis of complex organic molecules. In the context of ketone synthesis, transforming secondary alcohols to ketones is a critical example of this concept.

• Definition: The process of converting a specific functional group into another to alter molecular properties.
• Example: Transforming a hydroxyl group (OH) in secondary alcohols into a carbonyl group (C=O).
• Importance: Facilitates the creation of diverse and functional organic compounds.

By mastering functional group transformations, chemists can design more efficient synthetic pathways, optimize reaction conditions, and create compounds with desired properties. This strategy not only helps in ketone synthesis but is a cornerstone in developing a wide range of organic reactions, enabling advancements in materials science, pharmaceuticals, and synthesis technologies.