Question

Write equations for the following reactions, representing the reactants and products using structural formulas. (a) The hydrolysis of the amide \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CONHCH}_{3}\) to form benzoic acid and methylamine (b) The hydrolysis of \(\left(-\mathrm{CO}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CONH}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{NH}-\right)_{n}\) (nylon-6,6, a polyamide) to give a carboxylic acid and an amine

Short answer

(a) Hydrolysis: C₆H₅CONHCH₃ + H₂O → C₆H₅COOH + CH₃NH₂ (b) Nylon-6,6 Hydrolysis: [-CO-(CH₂)₄-CO-NH-(CH₂)₆-NH-]ₙ + 2n H₂O → n HOOC-(CH₂)₄-COOH + n H₂N-(CH₂)₆-NH₂

Step-by-step solution

Write Chemical Equation for Hydrolysis of Amide

For the hydrolysis of an amide, we add water (H₂O) to break the amide bond. In this case, the amide given is C₆H₅CONHCH₃. The hydrolysis reaction will produce benzoic acid (C₆H₅COOH) and methylamine (CH₃NH₂). The chemical equation is:\[\text{C}_6\text{H}_5\text{CONHCH}_3 + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_5\text{COOH} + \text{CH}_3\text{NH}_2\]

Write Structural Formulas for Hydrolysis of Amide

Using structural formulas, represent the reactants and products in the equation:\[\text{C}_6\text{H}_5\text{C(O)NHCH}_3 + \text{H-OH} \rightarrow \text{C}_6\text{H}_5\text{C(O)OH} + \text{CH}_3\text{NH}_2\]On the reactant side, the structure for the amide group CONH is shown, and the product side includes the carboxylic acid (COOH) and the amine (NH₂) group.

Overview of Nylon-6,6 Hydrolysis

Nylon-6,6 is a polyamide that consists of repeating units formed from the reaction of adipoyl chloride (a molecule with two acyl chloride groups, -COCl) and hexamethylenediamine (a molecule with two amino groups, -NH₂). Its hydrolysis involves adding water across each amide bond in the polymer.

Write Chemical Equation for Hydrolysis of Nylon-6,6

The chemical equation for the complete hydrolysis of the repeating unit of nylon-6,6 can be expressed by breaking the polymer chain at the amide bonds. Hydrolysis gives carboxylic acid and amine:\[\text{[-CO-(CH}_2)_4\text{-CO-NH-(CH}_2)_6\text{-NH-]}_n + 2n \text{ H}_2\text{O} \rightarrow\ n \text{ HOOC-(CH}_2)_4\text{-COOH} + n \text{ H}_2\text{N-(CH}_2)_6\text{-NH}_2\]

Write Structural Formulas for Hydrolysis of Nylon-6,6

Present the structural formulas of the reactants and products of nylon-6,6:Reacting repeating unit:\[\text{O=C}-(\text{CH}_2)_4\text{-C(=O)-NH-(CH}_2)_6\text{-NH-}\]Products after hydrolysis:\[\text{HOOC-(CH}_2)_4\text{-COOH} + \text{H}_2\text{N-(CH}_2)_6\text{-NH}_2\]This results in adipic acid and hexamethylenediamine.

Key concepts

Amide Bond

An amide bond is a type of covalent bond that connects a carbonyl group (C=O) to a nitrogen atom (NH). It's a key structural feature in both proteins and synthetic polymers. In the given exercise, we see an example of an amide bond in the compound \( \mathrm{C}_{6}\mathrm{H}_{5}\mathrm{CONHCH}_{3} \). During hydrolysis, this bond is broken to produce a carboxylic acid and an amine.
The process involves the addition of water, which effectively "adds" an OH group to the carbonyl carbon and an H to the nitrogen, splitting the original structure into two separate molecules. This is a common reaction in breaking down proteins in biological systems and synthetic materials like polyamides.
When you see an amide bond, you can often predict that hydrolysis will split it into distinct entities: the carbonyl part becomes a carboxylic acid, and the nitrogen part forms an amine.

Benzoic Acid

Benzoic acid is an aromatic carboxylic acid with the formula \( \mathrm{C}_6\mathrm{H}_5\mathrm{COOH} \). It appears as a product in the hydrolysis of certain amides, like \( \mathrm{C}_{6}\mathrm{H}_{5}\mathrm{CONHCH}_{3} \). This compound is commonly used in food preservation and has a characteristic weak acidic behavior.
The key structural feature of benzoic acid is the benzene ring (C₆H₅), which attaches to a carboxyl group (COOH). The presence of this ring makes benzoic acid a stable compound with interesting reactivity patterns. It also imparts unique solubility properties that can be manipulated in chemical processes.

• The benzene ring provides aromatic stability.
• The carboxyl group allows it to participate in hydrogen bonding, influencing its acidic nature.

Understanding its formation as a product of hydrolysis helps unveil many reactions associated with aromatic compounds.

Methylamine

Methylamine, with the chemical formula \( \mathrm{CH}_3\mathrm{NH}_2 \), is a simple amine derived from ammonia by replacing one hydrogen with a methyl group. It's a product that emerges from hydrolysis reactions involving amides.
In the given reaction, methylamine is obtained when the amide bond within \( \mathrm{C}_{6}\mathrm{H}_{5}\mathrm{CONHCH}_{3} \) undergoes hydrolysis. This small, volatile molecule exhibits strong basicity and is frequently used in the production of pharmaceuticals and other chemicals.

• Methylamine can accept a proton due to its lone pair of electrons on the nitrogen atom.
• Its basicity makes it a candidate for participating in further chemical transformations.

This component highlights the transforming nature of amines when produced through hydrolysis.

Nylon-6,6

Nylon-6,6 is a synthetic polymer known for its strength and resistance to abrasion. It is called a polyamide because it contains repeating amide bonds, similar to proteins' peptide chains. The hydrolysis of nylon-6,6 involves breaking down these amide links.
The repeating unit of nylon-6,6, formed from adipoyl chloride and hexamethylenediamine, features an amide bond that is the target in hydrolysis reactions. Hydrolysis, breaking down nylon-6,6, results in monomers such as adipic acid and hexamethylenediamine.

• Nylon-6,6 is widely used in textiles and engineering components.
• Hydrolysis disrupts its structure, reducing the polymer to its monomeric precursors.

Mainly, this process can be used to recycle the nylon, reclaiming valuable starting materials.

Polyamide

Polyamides are a family of polymers that possess amide bonds along their backbone chains. Apart from natural polyamides like proteins, synthetic examples include nylon, Kevlar, and other robust materials. Their properties include durability, flexibility, and heat resistance.
The formation of polyamides usually involves a condensation reaction between a diacid and a diamine, with water as a by-product. In the context of the exercise, the polyamide nylon-6,6 undergoes hydrolysis to deconstruct into smaller, more manageable components.

• Polyamides like nylon are used in automotive and textile industries.
• The hydrolysis of polyamides is often employed in waste treatment and recycling processes.

By understanding the nature of polyamides and their reactions, you can appreciate their widespread applications and the chemical processes used to manipulate them.