Problem 187 - A Complete Resource Book in Chemistry for JEE Main

Question

On vigorous oxidation by permanganate solution, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{CHCH}_{2} \mathrm{CHO}\) gives [2002] (a) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}\) and \(\mathrm{OHCCH}_{2} \mathrm{CHO}\) (b) CC(O)C(O)CC=O (c) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}\) and \(\mathrm{OHCCH}_{2} \mathrm{COOH}\) (d) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}\) and \(\mathrm{CH}_{3} \mathrm{COOH}\)

Step-by-Step Solution

Answer

(c) \((\mathrm{CH}_{3})_{2} \mathrm{CO}\) and \(\mathrm{OHCCH}_{2}\mathrm{COOH}\).

Step 1: Understanding the Reaction

We need to determine the products of the oxidation of \((\mathrm{CH}_{3})_{2} \mathrm{C}=\mathrm{CHCH}_{2} \mathrm{CHO}\) using a permanganate solution. Permanganate is a strong oxidizing agent that can oxidize alkenes and aldehydes to ketones or carboxylic acids.

Step 2: Analyzing the Double Bond

The compound \((\mathrm{CH}_{3})_{2} \mathrm{C}=\mathrm{CHCH}_{2} \mathrm{CHO}\) contains a double bond at the \((\mathrm{CH}_{3})_{2} \mathrm{C}=\mathrm{CH}-\) section. Oxidation of a terminal double bond with permanganate leads to cleavage, breaking the compound into two parts: \(\mathrm{CH}_{3}\) groups converting to acetone \((\mathrm{CH}_{3})_{2} \mathrm{CO}\).

Step 3: Analyzing the Aldehyde Group

The remaining part after cleavage is an aldehyde \(\mathrm{-CH}_{2}\mathrm{CHO}\). Strong oxidation by permanganate converts aldehydes to carboxylic acids. Hence, \(\mathrm{OHCCH}_{2}\mathrm{CHO}\) is converted to \(\mathrm{OHCCH}_{2}\mathrm{COOH}\).

Step 4: Identifying the Correct Option

Putting it all together, the products from vigorous oxidation are \((\mathrm{CH}_{3})_{2} \mathrm{CO}\) and \(\mathrm{OHCCH}_{2}\mathrm{COOH}\). Comparing with the options: (c) \((\mathrm{CH}_{3})_{2} \mathrm{CO}\) and \(\mathrm{OHCCH}_{2}\mathrm{COOH}\) matches the derived products.

Key Concepts

Oxidation Reactions

Oxidation reactions are chemical processes where a molecule loses electrons, commonly involving the addition of oxygen or the removal of hydrogen. In organic chemistry, oxidation often transforms an organic molecule to a more oxygen-rich form.
One common oxidizing agent used in laboratory settings is potassium permanganate ( MnO_4^{−}). It is a strong oxidizer that can react with alkenes and aldehydes to produce different types of products.

• Alkenes are oxidized to produce ketones or undergo complete cleavage to form simpler carbonyl compounds.
• Aldehydes, on the other hand, are typically oxidized to form carboxylic acids.

Understanding how these reactions occur can help in the synthesis or degradation of complex molecules, allowing chemists to predict or synthesize desired compounds and mixtures.

Alkenes

Alkenes are hydrocarbons that contain one or more carbon-carbon double bonds. These double bonds are reactive sites in the molecule that can undergo various chemical transformations.
When alkenes are treated with oxidizing agents like permanganate, they are transformed by the addition of oxygen atoms or by the cleavage of the double bond itself.

• Terminal alkenes (those at the end of a carbon chain) are often cleaved completely, with the resulting carbon fragments oxidized to carbonyl compounds such as ketones or carboxylic acids.
• For example, the terminal double bond in the molecule ( (CH_{3})_{2}C=CHCH_{2}CHO ) is oxidized by permanganate to produce acetone ( (CH_{3})_{2}CO ) and other oxidized products.

This interaction highlights the unique reactivity of the alkene functional group in oxidation reactions.

Aldehydes

Aldehydes are organic compounds containing a carbonyl group bonded to at least one hydrogen atom. This group, denoted as -CHO, is highly reactive.
In particular, aldehydes are susceptible to oxidation due to the presence of this easily oxidizable hydrogen.

• When oxidized, aldehydes are usually transformed into carboxylic acids.
• For instance, in the oxidation reaction discussed in the exercise, the aldehyde (-CH_{2}CHO) in the compound is oxidized to the corresponding carboxylic acid, aiding in the molecule’s transformation and breakdown.

This step is crucial in industrial processes and organic synthesis, where controlled oxidation is necessary to produce different compounds.

Carboxylic Acids

Carboxylic acids are characterized by the presence of a carboxyl group, (-COOH), which is a strong organic acid.
They are often the endpoint of oxidation reactions involving organic compounds, due to their stable oxidation state.

• During vigorous oxidation using strong oxidizers such as permanganate, aldehydes and some alkenes convert to carboxylic acids.
• In the given problem, the oxidation of the species (-CH_{2}CHO) leads to the formation of (-CH_{2}COOH), exemplifying this form of conversion.

Understanding the formation of carboxylic acids in oxidation reactions is vital since they are crucial in the synthesis of polymers, esters, and other important chemicals in the industry.