Question

On vigorous oxidation by permanganate solution, \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{CHCH}_{2} \mathrm{CHO}\) gives: (a) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO}\) and \(\mathrm{OHCCH}_{2} \mathrm{CHO}\) (b) (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 \(\mathrm{CH}_{2}(\mathrm{COOH})_{2}\)

Short answer

The products are (d) \((\mathrm{CH}_{3})_{2} \mathrm{CO}\) and \(\mathrm{CH}_{2}(\mathrm{COOH})_{2}\).

Step-by-step solution

Identify the Reaction

The compound given, \((\mathrm{CH}_{3})_{2} \mathrm{C}=\mathrm{CHCH}_{2} \mathrm{CHO}\), is being oxidized by a strong oxidizing agent, permanganate. This reaction typically oxidizes alkenes and aldehyde groups to carboxylic acids or ketones.

Predict Expected Products

On vigorous oxidation with permanganate, the double bond (\(\mathrm{C}=\mathrm{C}\)) is broken, and the aldehyde group (\(\mathrm{CHO}\)) is also oxidized. Ketones typically remain unchanged under these conditions.

Analyze Each Section of the Molecule

The double bond between \(\mathrm{CH}_{2}\) and \(\mathrm{C}(\mathrm{CH}_{3})_{2}\) when oxidatively cleaved results in one terminal methyl ketone, \((\mathrm{CH}_{3})_{2} \mathrm{CO}\). The rest of the molecule represents an aldehyde group which will be oxidized to a carboxylic acid, \(\mathrm{OHCCH}_{2} \rightarrow \mathrm{CH}_{2}(\mathrm{COOH})_{2}\).

Combine Oxidation Results

With the alkene and aldehyde oxidized, the products are \((\mathrm{CH}_{3})_{2} \mathrm{CO}\) from the alkene split and \(\mathrm{CH}_{2}(\mathrm{COOH})_{2}\) from the aldehyde oxidation.

Verify with Options

From the listed options, (d) \((\mathrm{CH}_{3})_{2} \mathrm{CO}\) and \(\mathrm{CH}_{2}(\mathrm{COOH})_{2}\) match the predicted products from the oxidation reaction.

Key concepts

Oxidation Reactions

Oxidation reactions in organic chemistry are a fundamental type of chemical transformation where a molecule undergoes a change in oxidation state, typically involving the loss of electrons. These reactions often result in an increase in the number of bonds to more electronegative elements such as oxygen. In simpler terms, oxidation can "add oxygen" or "remove hydrogen" from organic molecules.

A classic example in organic reactions is the conversion of an alcohol into a ketone or an aldehyde into a carboxylic acid. The presence of strong oxidizing agents, such as permanganate (\(\text{KMnO}_4\)), can facilitate the oxidation process. These agents are renowned for their ability to break carbon-carbon double bonds and transform certain functional groups, like aldehydes, into their oxidized forms. Without a proper understanding of oxidation reactions, predicting the outcome of such transformations could be tricky, which is why breakdown exercises are crucial in grasping these concepts.

Permanganate Oxidation

Permanganate oxidation is a common and powerful method used in organic chemistry to oxidize various types of organic molecules. This process utilizes potassium permanganate (\(\text{KMnO}_4\)) as the oxidizing agent, usually in an aqueous medium. Permanganate is noted for its reddish-purple color, which changes to a brown or colorless state as it reduces, indicating the oxidation of the organic substrate.

Key features of permanganate oxidation include:

• Breaking of carbon-carbon double bonds, transforming alkenes into vicinal diols or further oxidizing them depending on the conditions.
• Conversion of aldehyde groups into carboxylic acids, while ketones often remain unaffected.

The reaction conditions, like temperature and concentration, can influence the extent and type of oxidation that occurs. Vigorous conditions will typically lead to more complete oxidation, such as the conversion of an alkene's double bond and aldehyde groups into carboxylic acids, as demonstrated in the exercise example.

Carboxylic Acids

Carboxylic acids are a major class of organic compounds characterized by the presence of a carboxyl group (-COOH). This functional group is highly reactive and plays an integral role in various chemical reactions. Carboxylic acids often emerge as the end products of oxidation reactions involving aldehydes or alcohols.

Understanding their formation is crucial when studying oxidation reactions. For instance, in the presence of a strong oxidizing agent such as permanganate, aldehydes are typically oxidized to carboxylic acids. This transformation involves the addition of an oxygen atom to the aldehyde, effectively increasing its oxidation state and converting it into the acid form.

Carboxylic acids are recognized by their acidic nature, manifesting in their ability to donate protons (H\(^{+}\)) in aqueous solutions. They also exhibit significant hydrogen bonding due to the presence of both a hydroxyl (-OH) and carbonyl (C=O) group, leading to higher melting and boiling points compared to other similar-sized organic molecules.

Ketones

Ketones are a class of organic compounds identified by the presence of a carbonyl group (C=O) bonded to two carbon atoms. This functional group provides ketones with distinct chemical properties and reactivity patterns.

In the context of oxidation reactions, ketones generally exhibit resistance to further oxidation under mild conditions, such as those employing permanganate. This is due to the stability of the ketone's carbonyl group, which is less reactive compared to aldehydes. As described in the exercise, ketones are left unchanged when using strong oxidizing agents like permanganate, making them integral markers in oxidation reactions.

Ketones are versatile in synthesis and widely used in various industrial applications, including the production of solvents, perfumes, and as intermediates in the manufacturing of pharmaceuticals. Their presence in an organic molecule can influence the pathway and outcome of reactions, particularly in multi-step transformations.