Question

Reaction in which amino acid is not obtained as a product is (A) CC(=O)CCCC(N)=O \(\frac{\text { (i) } \mathrm{KOBr} \text { (excess) }}{\text { (ii) } \mathrm{H}_{3} \mathrm{O}^{\oplus}}\) (B) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{NH} \frac{\text { (i) } \mathrm{KCN}}{\text { (ii) } \mathrm{H}_{2} \mathrm{O} / \mathrm{H}^{\mathrm{q}}}\) (C) (D) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{O} \frac{\text { (i) } \mathrm{KCN}}{\text { (ii) } \mathrm{H}_{2} \mathrm{O} / \mathrm{H}^{\mathrm{F}}}{\longrightarrow}\)

Short answer

The reaction in which an amino acid is not obtained as a product is (D) \(CH_3-CH=O\), KCN, \(H_2O / H^+\). In this reaction, an α-hydroxy acid is formed instead of an amino acid.

Step-by-step solution

Identify the components and reactants

In each given reaction, we have various reactants and reagents. Let's list them down for each reaction: (A) \(CC(=O)CCCC(N)=O\), KOBr (excess), \(H_3O^+\) (B) \(CH_3-CH=NH\), KCN, \(H_2O / H^+\) (C) No reactants given (invalid option) (D) \(CH_3-CH=O\), KCN, \(H_2O / H^+\) #Step 2: Analyze each reaction and determine the product#

Analyze each reaction and determine the product

Now we will analyze each reaction, identify the product, and determine if an amino acid is formed. (A) In this reaction, amino acid is the starting compound. KOBr (excess) will result in Hofmann degradation, which causes the removal of one carbon atom and yields a primary amine. Finally, the reaction with \(H_3O^+\) will lead to the formation of a new amino acid. So, amino acid is formed as a product in this reaction. (B) The starting compound is an imine, and when reacted with KCN, it forms a cyanohydrin followed by hydrolysis in the presence of \(H_2O / H^+\), forming an α-amino acid. So, an amino acid is formed as a product in this reaction as well. (D) The starting compound is an aldehyde, and when reacted with KCN, it forms a cyanohydrin followed by hydrolysis in the presence of \(H_2O / H^+\), forming an α-hydroxy acid. In this case, an amino acid is not formed as a product. Therefore the answer is (D).

Key concepts

Hofmann Degradation

Hofmann degradation is a chemical reaction that involves the conversion of amides to amines with one less carbon atom. This process is particularly useful in synthesizing primary amines from amides. The degradation is achieved using an alkaline oxidizing agent such as bromine and potassium hydroxide, commonly referred to as KOBr. The general reaction sequence is as follows:

• The amide is first treated with excess KOBr, which forms an intermediate.
• This intermediate undergoes rearrangement and removal of a carbonyl group, effectively shortening the carbon chain by one unit.
• Finally, the rearranged compound is hydrolyzed to yield the amine.

Chemically, the reaction is advantageous as it provides a simple method to produce primary amines, which are valuable in various chemical syntheses. Through Hofmann degradation, complex amide structures can be simplified while retaining their functional utility.

Imines

Imines are organic compounds characterized by the presence of a carbon-nitrogen double bond, analogous to carbonyl compounds such as ketones and aldehydes. Structurally, they can be represented as R1R2C=NR3, where R1, R2, and R3 can be hydrogen or organic substituents.

• Imines are typically formed by the condensation of aldehydes or ketones with primary amines under dehydrating conditions.
• The process involves the removal of water, resulting in the formation of a C=N bond.

In the context of amino acid synthesis, imines play a crucial role. Through subsequent reactions, such as nucleophilic additions, imines can be manipulated to form other functional groups, paving the way for diverse synthetic applications. For example, reaction with hydrogen cyanide can convert imines into cyanohydrins, which serve as intermediates in further chemical transformations.

Cyanohydrin Formation

Cyanohydrins are organic compounds that feature a cyano group (CN) and a hydroxyl group (OH) bonded to the same carbon atom. They are formed through a reaction known as cyanohydrin formation, which involves the nucleophilic addition of hydrogen cyanide (HCN) to aldehydes or ketones.

• In this reaction, the cyano group acts as a nucleophile, attacking the carbonyl carbon, resulting in the opening of the carbonyl double bond.
• Simultaneously, the carbonyl oxygen is protonated, forming the hydroxyl group and yielding a cyanohydrin.

Cyanohydrins are important intermediates in organic synthesis, particularly in the production of α-amino acids and α-hydroxy acids. Their versatility allows for subsequent transformations through reactions like hydrolysis, where the cyano group can be converted into different chemical functionalities. These compounds are also significant in pharmaceuticals and agrochemicals, offering pathways to synthesize various compounds with medicinal properties.

Hydrolysis Reactions

Hydrolysis reactions involve the breakdown of a compound through the reaction with water. This process is fundamental in chemistry, particularly in transforming functional groups and breaking down complex molecules into simpler ones.

• When hydrolyzing cyanohydrins, the cyano group is converted into a carboxylic acid or an amine group, based on the reaction conditions.
• In acidic solutions, hydrolysis can lead to the formation of α-amino acids, important building blocks in biology and chemistry.

Hydrolysis of organic compounds often involves using a catalyst, like an acid or base, to increase the rate of reaction. This reaction type is significant not only in chemical synthesis but also in biological systems where it helps in the digestion of biomolecules. In amino acid synthesis, hydrolysis is a key step, translating intermediate compounds into valuable amino acids which can be further utilized in synthesizing proteins and peptides.