Question

The reaction in which one of the major product is carboxylic acid / acid salt. (A) Haloform reaction (B) Cannizaro's reaction (C) Perkin reaction (D) Benzil-benzilic acid rearrangement

Short answer

All the given reactions, (A) Haloform reaction, (B) Cannizaro's reaction, (C) Perkin reaction, and (D) Benzil-benzilic acid rearrangement have carboxylic acid or acid salt as one of their major products.

Step-by-step solution

Examine the Haloform reaction

In the haloform reaction, a methyl ketone reacts with a halogen to form a haloform (such as chloroform or iodoform) and a carboxylate ion. In this reaction, carboxylic acid or acid salt is a major product.

Examine the Cannizaro's reaction

In Cannizaro's reaction, an aldehyde without alpha-hydrogen reacts with a base such as an alkali to form a carboxylic acid and an alcohol. In this reaction, carboxylic acid or acid salt is a major product.

Examine the Perkin reaction

The Perkin reaction involves the reaction of an aromatic aldehyde with an anhydride in the presence of a base, which yields an α,β-unsaturated carboxylic acid. In this reaction, carboxylic acid is a major product.

Examine the Benzil-benzilic acid rearrangement

The Benzil-Benzilic acid rearrangement is a rearrangement reaction involving the conversion of a 1,2-diketone (Benzil) to an α-hydroxy carboxylic acid (Benzilic acid) using an alkoxide base. In this reaction, carboxylic acid is a major product.

Analyze the Information and Select the Correct Option

Based on our analysis, we can conclude that all options (A), (B), (C), and (D) are reactions where carboxylic acid or acid salt is one of the major products.

Key concepts

Haloform Reaction

The Haloform reaction is a chemical reaction that occurs when a methyl ketone comes into contact with a halogen, such as chlorine, bromine, or iodine, in the presence of a base. This reaction leads to the formation of a carboxylate ion and a haloform, like chloroform or iodoform. The mechanism involves:

• Halogenation of the methyl group to form trihalomethyl ketone.
• Base-induced cleavage resulting in a carboxylate ion and a haloform.

The carboxylate ion is then often converted to a carboxylic acid if the reaction is conducted in acidic conditions. This reaction is particularly useful in organic synthesis for its ability to introduce a variety of functional groups.

Cannizaro's Reaction

Cannizaro's reaction is a notable redox reaction where aldehydes without α-hydrogens are treated with strong bases, resulting in the disproportionation of the aldehyde into an alcohol and a carboxylic acid. The steps can be detailed as follows:

• The base attacks the carbonyl group, forming an alkoxide intermediate.
• This intermediate transfers a hydride to a second molecule of the aldehyde, creating the alcohol and a carboxylate ion.

This reaction is unique in forming two different oxygen-containing products from a single type of aldehyde, underlining its significance in organic chemistry.

Perkin Reaction

The Perkin reaction is typically used to synthesize α,β-unsaturated aromatic acids. This reaction involves the condensation of an aromatic aldehyde with an anhydride in the presence of a base, leading to the formation of an enolate intermediate that attacks the aldehyde carbonyl group. The Perkin reaction proceeds through several steps:

• Formation of the enolate ion from the anhydride.
• Attack on the aromatic aldehyde to form a β-hydroxy acid.
• Dehydration to yield the α,β-unsaturated acid.

The obtained carboxylic acid serves as a cornerstone in the synthesis of various medicinal and fragrant compounds.

Benzil-Benzilic Acid Rearrangement

The Benzil-Benzilic acid rearrangement is a fascinating transformation that converts a 1,2-diketone, such as Benzil, into a α-hydroxy carboxylic acid, Benzilic acid. This rearrangement is induced by an alkoxide base and involves the following steps:

• Formation of a cyclic intermediate by base attack on the carbonyl group of Benzil.
• Rearrangement and ring opening to yield a carboxylate ion.
• Acidification which transforms the carboxylate ion into benzilic acid.

Such rearrangement reactions showcase vital principles of stability and electron shifts in organic molecules.

Carboxylic Acid Formation

Formation of carboxylic acids is a fundamental process in organic chemistry, intrinsic to various reactions including oxidation of alcohols, hydrolysis of nitriles, and metal-catalyzed carbonylation. The common attribute of these reactions is the introduction or enhancement of an oxygen-containing functional group.
Key considerations in forming carboxylic acids include:

• Origin of the starting material, such as aldehydes, ketones, or alkenes.
• Use of oxidizing agents or catalysts to drive the reaction towards carboxylation.
• Control of conditions such as temperature and pH to optimize yields.

The versatility and importance of carboxylic acids in synthesizing pharmaceuticals and polymers underscore their indispensable nature in chemistry.