When polyethylene is made by free radical polymerization , the resulting polymer has a significant amount of branching, resulting in low-density polyethylene. When styrene undergoes free radical polymerization, on the other hand, very little branching occurs. This phenomenon is to be explained. Concept introduction: Free radical polymerization is an example of chain-growth polymerization, one general class of polymerization reactions. In chain-growth polymerization, reaction occurs at the end of the growing chain, and each reaction lengthens the polymer chain by a single repeating unit. Branching can occur during chain-growth polymerization if the reactive site becomes located somewhere in the middle of a chain. The free radical at one end of one growing chain encounters a hydrogen atom in the middle of another chain. After hydrogen atom abstraction, the original free radical has become a terminated closed-shell species and the reactive radical appears somewhere in the middle of another chain. Further polymerization at the new radical creates a branch in the chain. Due to this reason, polyethylene has a significant amount of branching. But in polystyrene, phenyl groups are present which sterically hinder the radicals that may abstract H atoms. Therefore, the bulky phenyl rings prevent branching.

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Answer 1

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Definition Definition Chemical process in which one or more monomers combine to produce a very large chain-like molecule called a polymer. The functional groups present on the monomers and their steric effects are responsible for polymerization through a sequence of reactions that vary in complexity. There exists a stable covalent chemical bond between monomers that sets apart polymerization from other processes.

Chapter 26, Problem 26.50P

Interpretation Introduction

Interpretation:

When polyethylene is made by free radical polymerization, the resulting polymer has a significant amount of branching, resulting in low-density polyethylene. When styrene undergoes free radical polymerization, on the other hand, very little branching occurs. This phenomenon is to be explained.

Concept introduction:

Free radical polymerization is an example of chain-growth polymerization, one general class of polymerization reactions. In chain-growth polymerization, reaction occurs at the end of the growing chain, and each reaction lengthens the polymer chain by a single repeating unit. Branching can occur during chain-growth polymerization if the reactive site becomes located somewhere in the middle of a chain. The free radical at one end of one growing chain encounters a hydrogen atom in the middle of another chain. After hydrogen atom abstraction, the original free radical has become a terminated closed-shell species and the reactive radical appears somewhere in the middle of another chain. Further polymerization at the new radical creates a branch in the chain. Due to this reason, polyethylene has a significant amount of branching. But in polystyrene, phenyl groups are present which sterically hinder the radicals that may abstract H atoms. Therefore, the bulky phenyl rings prevent branching.

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Answer 2

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Definition Definition Chemical process in which one or more monomers combine to produce a very large chain-like molecule called a polymer. The functional groups present on the monomers and their steric effects are responsible for polymerization through a sequence of reactions that vary in complexity. There exists a stable covalent chemical bond between monomers that sets apart polymerization from other processes.

Chapter 26, Problem 26.50P

Interpretation Introduction

Interpretation:

When polyethylene is made by free radical polymerization, the resulting polymer has a significant amount of branching, resulting in low-density polyethylene. When styrene undergoes free radical polymerization, on the other hand, very little branching occurs. This phenomenon is to be explained.

Concept introduction:

Free radical polymerization is an example of chain-growth polymerization, one general class of polymerization reactions. In chain-growth polymerization, reaction occurs at the end of the growing chain, and each reaction lengthens the polymer chain by a single repeating unit. Branching can occur during chain-growth polymerization if the reactive site becomes located somewhere in the middle of a chain. The free radical at one end of one growing chain encounters a hydrogen atom in the middle of another chain. After hydrogen atom abstraction, the original free radical has become a terminated closed-shell species and the reactive radical appears somewhere in the middle of another chain. Further polymerization at the new radical creates a branch in the chain. Due to this reason, polyethylene has a significant amount of branching. But in polystyrene, phenyl groups are present which sterically hinder the radicals that may abstract H atoms. Therefore, the bulky phenyl rings prevent branching.

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Answer 3

Question

Definition Definition Chemical process in which one or more monomers combine to produce a very large chain-like molecule called a polymer. The functional groups present on the monomers and their steric effects are responsible for polymerization through a sequence of reactions that vary in complexity. There exists a stable covalent chemical bond between monomers that sets apart polymerization from other processes.

Chapter 26, Problem 26.50P

Interpretation Introduction

Interpretation:

When polyethylene is made by free radical polymerization, the resulting polymer has a significant amount of branching, resulting in low-density polyethylene. When styrene undergoes free radical polymerization, on the other hand, very little branching occurs. This phenomenon is to be explained.

Concept introduction:

Free radical polymerization is an example of chain-growth polymerization, one general class of polymerization reactions. In chain-growth polymerization, reaction occurs at the end of the growing chain, and each reaction lengthens the polymer chain by a single repeating unit. Branching can occur during chain-growth polymerization if the reactive site becomes located somewhere in the middle of a chain. The free radical at one end of one growing chain encounters a hydrogen atom in the middle of another chain. After hydrogen atom abstraction, the original free radical has become a terminated closed-shell species and the reactive radical appears somewhere in the middle of another chain. Further polymerization at the new radical creates a branch in the chain. Due to this reason, polyethylene has a significant amount of branching. But in polystyrene, phenyl groups are present which sterically hinder the radicals that may abstract H atoms. Therefore, the bulky phenyl rings prevent branching.

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Answer 4

Question

Definition Definition Chemical process in which one or more monomers combine to produce a very large chain-like molecule called a polymer. The functional groups present on the monomers and their steric effects are responsible for polymerization through a sequence of reactions that vary in complexity. There exists a stable covalent chemical bond between monomers that sets apart polymerization from other processes.

Chapter 26, Problem 26.50P

Interpretation Introduction