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 nylon-66, \(\left[-\mathrm{CO}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CONH}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{NH}-\right]_{x}\) a polyamide, to give a carboxylic acid and an amine

Short answer

(a) Hydrolysis forms benzoic acid and methylamine; (b) Hydrolysis of nylon-66 forms adipic acid and hexamethylenediamine.

Step-by-step solution

Identify Functional Groups and Hydrolysis Reaction

Hydrolysis of an amide typically involves breaking the carbon-nitrogen bond in the presence of water, resulting in the formation of a carboxylic acid and an amine. In part (a), the amide \( \text{C}_6\text{H}_5\text{CONHCH}_3 \) consists of a benzoyl group and a methylamine group. In part (b), nylon-66 is a polyamide composed of a repeating unit made of hexamethylenediamine and adipic acid. We will first consider the general reaction process for each.

Write Equation for Part (a) Hydrolysis

In part (a), the reactants are the amide \( \text{C}_6\text{H}_5\text{CONHCH}_3 \) and water (\( \text{H}_2\text{O} \)). The reaction forms benzoic acid (\( \text{C}_6\text{H}_5\text{COOH} \)) and methylamine (\( \text{CH}_3\text{NH}_2 \)). The structural equation is:\[ \text{C}_6\text{H}_5\text{CONHCH}_3 + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_5\text{COOH} + \text{CH}_3\text{NH}_2 \] This reaction involves the cleavage of the carbon-nitrogen bond and addition of water to form the new functional groups.

Write Equation for Part (b) Hydrolysis

For part (b), the hydrolysis of nylon-66 involves breaking the amide linkage in its repeating unit. Each unit\'s amide bond (\( \text{-CO-(CH}_2\text{)}_4 \text{CO-NH-(CH}_2\text{)}_6 \text{NH-} \)) will react with water to form a carboxylic acid and an amine. Specifically, adipic acid (\( \text{HOOC-(CH}_2\text{)}_4\text{-COOH} \)) and hexamethylenediamine (\( \text{H}_2\text{N-(CH}_2\text{)}_6\text{-NH}_2 \)) will be produced as follows: \[-\text{CO(CH}_2\text{)}_4\text{CONH(CH}_2\text{)}_6\text{NH}- + n\text{H}_2\text{O} \rightarrow n\text{HOOC(CH}_2\text{)}_4\text{COOH} + n\text{H}_2\text{N(CH}_2\text{)}_6\text{NH}_2\] This simplification shows the transformation of each repeating unit within the polymer.

Key concepts

Amide Functional Group

An amide functional group is an organic functional group characterized by a carbon atom bonded to a nitrogen atom (C-N). The carbon atom is also double-bonded to an oxygen atom (C=O), forming a carbonyl group. Amides are commonly found in various chemical and biological systems. For instance, the peptide bonds in proteins are essentially amide bonds.
The general formula for an amide is \ \( R_1- ext{C(O)NR}_2R_3 \), where \( R_1 \), \( R_2 \), and \( R_3 \) are organic substituents.
The amide's defining feature is its ability to participate in hydrolysis reactions. Hydrolysis refers to a reaction involving water that results in the breaking of the amide bond. It's significant because it converts an amide into a carboxylic acid and an amine. This reaction is depicted in the equations of focus, where hydrolysis transforms \( \text{C}_6\text{H}_5\text{CONHCH}_3 \) by splitting its carbon-nitrogen bond.

Structural Formulas

Structural formulas are a way of representing the molecular structure of a compound, showing the arrangement of atoms within the molecule. Unlike chemical formulas, which only provide the types and numbers of atoms, structural formulas depict the relationships and bonds between them.
When considering hydrolysis reactions, understanding the structural formula of a reactant provides insight into which bonds will break and what products will form. For example, the amide \( \text{C}_6\text{H}_5\text{CONHCH}_3 \) is illustrated as a distinct structure highlighting the benzoyl, carbonyl, and methylamine groups.
This detailed depiction is essential because visualizing how atoms are connected aids in predicting the reaction's outcomes. Specifically, for the hydrolysis reactions described, breaking the structural formula's carbon-nitrogen bond leads to identifiable products like carboxylic acids and amines, making structural formulas invaluable for understanding chemical processes.

Nylon-66 Hydrolysis

Nylon-66 is a type of polyamide, a polymer made from hexamethylenediamine and adipic acid. Its structure features repeating units connected by amide bonds. When subjected to hydrolysis, these amide bonds break, resulting in the formation of individual monomers.
The specific reaction here involves the hydrolysis of the repeating unit in nylon-66, represented as \(-\text{CO(CH}_2\text{)}_4\text{CONH(CH}_2\text{)}_6\text{NH}-\). Hydrolysis cleaves these amide linkages, yielding adipic acid \( \text{HOOC-(CH}_2\text{)}_4\text{-COOH} \) and hexamethylenediamine \( \text{H}_2\text{N-(CH}_2\text{)}_6\text{-NH}_2 \).
Understanding nylon-66 hydrolysis is crucial because it unravels polymers into their foundational components, which is a common method used in laboratory settings and industry to recycle or decompose synthetic polymers efficiently.

Chemical Reactions in Polymers

Polymer chemistry often focuses on the creation and transformation of large molecules consisting of repeated subunits or monomers. These reactions can involve polymerization, where monomers combine, or depolymerization, like the hydrolysis reactions discussed, which break them down.
Polymer hydrolysis is a specific type of chemical reaction important for understanding polymer life cycles and behavior. For example, breaking down synthetics like nylon-66 through hydrolysis is a strategic approach to manage waste or reprocess the materials. Both kitchen chemistry and industrial processes use controlled hydrolysis, enhancing or altering the qualities of polymer products.
Chemical reactions in polymers are complex yet fundamental, as they not only include the formation and alteration of macromolecules but also dictate the practicality and sustainability of materials in everyday applications.