Question

The intramolecular reaction of 5-aminopentanoic acid through nucleophilic acyl substitution would result in a(n): (A) anhydride. (B) lactone. (C) lactam. (D) carboxylic acid.

Short answer

The resulting product is a lactam (C).

Step-by-step solution

- Identify the Functional Groups

Note that 5-aminopentanoic acid has both an amino group (-NH2) and a carboxylic acid group (-COOH) on the same molecule.

- Analyze Possible Reactions

Consider how the amino group and carboxylic acid group can react with one another. The amino group can act as a nucleophile, attacking the carbonyl carbon of the carboxylic acid, leading to intramolecular cyclization.

- Determine the Product

The intramolecular reaction between the amino group and the carboxylic acid group would form a cyclic structure. This type of intramolecular reaction forms a ring, specifically a lactam, which is a cyclic amide.

- Select the Correct Option

Based on the type of reaction and the structure of the resulting compound, identify the correct name for the product. A cyclic amide formed by nucleophilic acyl substitution is called a 'lactam', so the correct answer is (C) lactam.

Key concepts

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction in organic chemistry. In this process, a nucleophile replaces a leaving group in a compound containing a carbonyl carbon (C=O). This type of reaction usually occurs in the presence of a strong nucleophile and an electrophilic carbonyl carbon.
For example, in the case of 5-aminopentanoic acid, the amino group (-NH2) acts as the nucleophile, while the carbonyl carbon of the carboxylic acid (-COOH) acts as the electrophile. When the amino group attacks the carbonyl carbon, it triggers the substitution, leading to the formation of a new bond and the release of a water molecule.
Steps involved in nucleophilic acyl substitution:

• The nucleophile approaches the electrophilic carbonyl carbon.
• The nucleophile donates its electron pair to form a new bond with the carbonyl carbon.
• The leaving group (in this case, -OH from the carboxylic acid) is expelled, forming the final product.

This reaction is crucial for forming various compounds like esters, amides, and lactams.

Lactam Formation

Lactam formation occurs when a molecule contains both an amino group and a carboxylic acid group, leading to an intramolecular reaction and the formation of a cyclic amide. Lactams are named based on the size of the ring formed, which can range from three-membered to large macromolecular rings.
In the example of 5-aminopentanoic acid, the molecule undergoes intramolecular cyclization because the nucleophilic amino group attacks the electrophilic carbonyl carbon of the carboxylic acid group. This reaction forms a cyclic amide known as a lactam.
Characteristics of lactam formation:

• It produces a stable ring structure.
• It involves intramolecular nucleophilic acyl substitution.
• Lactams are typically more stable than their linear counterparts.

The product of this reaction is essential in the synthesis of various natural and synthetic products, including pharmaceuticals.

Cyclic Compounds

Cyclic compounds are molecules where the atoms are connected to form a ring structure. These structures can consist of carbon and other elements like nitrogen, oxygen, or sulfur. The size of the ring and the nature of the atoms involved can significantly affect the compound's properties.
Cyclic compounds can be classified into different types based on the ring size and the elements involved. For instance, a five-membered ring with one nitrogen atom (as in the lactam formed from 5-aminopentanoic acid) is known as a pyrrolidone.
Important points about cyclic compounds:

• Cyclic structures can offer more stability compared to linear analogs due to ring strain considerations.
• Aromatic cyclic compounds, like benzene, have extra stability due to resonance.
• Many cyclic compounds play a vital role in biological systems and industrial applications.

Understanding cyclic compounds helps in various fields, including drug development, materials science, and molecular biology.