Chapter 31, Problem 31.44P

Although styrene undergoes both cationic and anionic polymerization equally well, one method is often preferred with substituted styrenes. Which method is preferred with each compound? Explain.

a. c.

b. d.

Interpretation Introduction

(a)

Interpretation: The method, anionic or cationic polymerization preferred with the given substituted styrene is to be identified, and an explanation corresponding to it is to be stated.

Concept introduction: An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

Answer to Problem 31.44P

The given substituted styrene prefers to undergo cationic polymerization, due to presence of electron releasing group on benzene ring.

Explanation of Solution

The given substituted styrene resembles to ${\text{CH}}_{\text{2}}=\text{CHZ}$ alkene, where $\text{Z}={\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{OCH}}_{\text{3}}$. This means benzene ring is substituted with methoxy group. The methoxy group is an electron releasing group.

An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

An electron releasing group releases electron density towards benzene ring and stabilizes carbocation formed during the cationic polymerization, whereas an electron withdrawing group withdraws electron density towards itself and stabilizes carbanion formed during the anionic polymerization.

Since the given substituted styrene involves bonding of an electron releasing group to benzene ring, it prefers to undergo cationic polymerization.

Interpretation Introduction

(b)

Interpretation:The method, anionic or cationic polymerization preferred with the given substituted styrene is to be identified, and an explanation corresponding to it is to be stated.

Concept introduction: An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

Answer to Problem 31.44P

The given substituted styrene prefers to undergo anionic polymerization, due to presence of electron withdrawing group on benzene ring.

Explanation of Solution

The given substituted styrene resembles to ${\text{CH}}_{\text{2}}=\text{CHZ}$ alkene, where $\text{Z}={\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{OCH}}_{\text{3}}$. This means benzene ring is substituted with nitro group. The nitro group is an electron withdrawing group.

An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

An electron releasing group releases electron density towards benzene ring and stabilizes carbocation formed during the cationic polymerization, whereas an electron withdrawing group withdraws electron density towards itself and stabilizes carbanion formed during the anionic polymerization.

Since the given substituted styrene involves bonding of an electron withdrawing group to benzene ring, it prefers to undergo anionic polymerization.

Interpretation Introduction

(c)

Interpretation:The method, anionic or cationic polymerization preferred with the given substituted styrene is to be identified, and an explanation corresponding to it is to be stated.

Concept introduction: An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

Answer to Problem 31.44P

The given substituted styrene prefers to undergo anionic polymerization, due to presence of electron withdrawing group on benzene ring.

Explanation of Solution

The given substituted styrene resembles to ${\text{CH}}_{\text{2}}=\text{CHZ}$ alkene, where $\text{Z}={\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{OCH}}_{\text{3}}$. This means benzene ring is substituted with ${\text{CF}}_{\text{3}}$ group. The ${\text{CF}}_{\text{3}}$ group is an electron withdrawing group.

An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

An electron releasing group releases electron density towards benzene ring and stabilizes carbocation formed during the cationic polymerization, whereas an electron withdrawing group withdraws electron density towards itself and stabilizes carbanion formed during the anionic polymerization.

Since the given substituted styrene involves bonding of an electron withdrawing group to benzene ring, it prefers to undergo anionic polymerization.

Interpretation Introduction

(d)

Interpretation:The method, anionic or cationic polymerization preferred with the given substituted styrene is to be identified, and an explanation corresponding to it is to be stated.

Concept introduction: An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

Answer to Problem 31.44P

The given substituted styrene prefers to undergo cationic polymerization, due to presence of electron releasing group on benzene ring.

Explanation of Solution

The given substituted styrene resembles to ${\text{CH}}_{\text{2}}=\text{CHZ}$ alkene, where $\text{Z}={\text{C}}_{\text{6}}{\text{H}}_{\text{4}}{\text{OCH}}_{\text{3}}$. This means benzene ring is substituted with ethyl group. The ethyl group is an electron releasing group.

An alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron withdrawing group as $\text{Z}$ group prefers to undergo anionic polymerization to yield addition polymers. On the other hand, an alkene $\left({\text{CH}}_{\text{2}}=\text{CHZ}\right)$ that contains electron releasing group as $\text{Z}$ group prefers to undergo cationic polymerization to yield addition polymers.

An electron releasing group releases electron density towards benzene ring and stabilizes carbocation formed during the cationic polymerization, whereas an electron withdrawing group withdraws electron density towards itself and stabilizes carbanion formed during the anionic polymerization.

Since the given substituted styrene involves bonding of an electron releasing group to benzene ring, it prefers to undergo cationic polymerization.

Conclusion

(a) The given substituted styrene prefers to undergo cationic polymerization, due to presence of an electron releasing group on benzene ring.

(b) The given substituted styrene prefers to undergo anionic polymerization, due to presence of an electron withdrawing group on benzene ring.

(c) The given substituted styrene prefers to undergo anionic polymerization, due to presence of an electron withdrawing group on benzene ring.

(d) The given substituted styrene prefers to undergo cationic polymerization, due to presence of an electron releasing group on benzene ring.