# Organic Chemistry I & II

Top Hat Intro Course - Organic Chemistry I & II is designed for instructors who want an active, dynamic, and understandable approach to support their own efforts in the classroom. This ever-evolving textbook includes auto-graded questions, videos and approachable language in order to make difficult concepts easier to understand and implement.

## What is a Top Hat Textbook?

Top Hat has reimagined the textbook – one that is designed to improve student readership through interactivity, is updated by a community of collaborating professors with the newest information, and accessed online from anywhere, at anytime.

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## Comparison of Organic Chemistry Textbooks

Consider adding Top Hat’s Organic Chemistry textbook to your upcoming course. We’ve put together a textbook comparison to make it easy for you in your upcoming evaluation.

### Top Hat

Steven Forsey, “Organic Chemistry”, Only one edition needed

### McGraw-Hill

Carey & Giuliano, “Organic Chemistry”, 10th Edition

### Wiley

Solomons et al., “Organic Chemistry”, 12th Edition

### Wiley

David R. Klein, “Organic Chemistry”, 3rd Edition

### Pricing

Average price of textbook across most common format

#### $219 Hardcover print text only ####$301

Hardcover print text only

#### $301 Hardcover print text only ### Always up-to-date content, constantly revised by community of professors Content meets standard for Introduction to Organic Chemistry course, and is updated with the latest content ### In-Book Interactivity Includes embedded multi-media files and integrated software to enhance visual presentation of concepts directly in textbook Only available with supplementary resources at additional cost Only available with supplementary resources at additional cost Only available with supplementary resources at additional cost ### Customizable Ability to revise, adjust and adapt content to meet needs of course and instructor ### All-in-one Platform Access to additional questions, test banks, and slides available within one platform ## Pricing Average price of textbook across most common format ### Top Hat Steven Forsey, “Organic Chemistry”, Only one edition needed #### Up to40-60%more affordable Lifetime access on any device ### McGraw-Hill Carey & Giuliano, “Organic Chemistry”, 10th Edition ####$219

Hardcover print text only

### Wiley

Solomons et al., “Organic Chemistry”, 12th Edition

#### $301 Hardcover print text only ### Wiley David R. Klein, “Organic Chemistry”, 3rd Edition ####$301

Hardcover print text only

## Always up-to-date content, constantly revised by community of professors

Constantly revised and updated by a community of professors with the latest content

### Top Hat

Steven Forsey, “Organic Chemistry”, Only one edition needed

### McGraw-Hill

Carey & Giuliano, “Organic Chemistry”, 10th Edition

### Wiley

Solomons et al., “Organic Chemistry”, 12th Edition

### Wiley

David R. Klein, “Organic Chemistry”, 3rd Edition

## In-book Interactivity

Includes embedded multi-media files and integrated software to enhance visual presentation of concepts directly in textbook

### Top Hat

Steven Forsey, “Organic Chemistry”, Only one edition needed

### McGraw-Hill

Carey & Giuliano, “Organic Chemistry”, 10th Edition

### Wiley

Solomons et al., “Organic Chemistry”, 12th Edition

### Wiley

David R. Klein, “Organic Chemistry”, 3rd Edition

## Customizable

Ability to revise, adjust and adapt content to meet needs of course and instructor

### Top Hat

Steven Forsey, “Organic Chemistry”, Only one edition needed

### McGraw-Hill

Carey & Giuliano, “Organic Chemistry”, 10th Edition

### Wiley

Solomons et al., “Organic Chemistry”, 12th Edition

### Wiley

David R. Klein, “Organic Chemistry”, 3rd Edition

## All-in-one Platform

### Top Hat

Steven Forsey, “Organic Chemistry”, Only one edition needed

### McGraw-Hill

Carey & Giuliano, “Organic Chemistry”, 10th Edition

### Wiley

Solomons et al., “Organic Chemistry”, 12th Edition

### Wiley

David R. Klein, “Organic Chemistry”, 3rd Edition

#### Dr. Steven Forsey, Ph.D.University of Waterloo

Steven Forsey is currently a Professor at University of Waterloo, teaching a variety of organic chemistry courses to Chemistry, Science, Chemical Engineering, Nanotechnology and distance education students. He received his Ph.D. (2004) for Synthetic Organic Chemistry from University of Waterloo, Ontario. He is a recipient of the Excellence of Science Teaching Award and has acted as the Teaching Fellow for the Department of Chemistry since 2016.

## Explore this textbook

Read the fully unlocked textbook below, and if you’re interested in learning more, get in touch to see how you can use this textbook in your course today.

# Chapter 27: Synthetic Polymers

## Learning Objectives

• Understand that polymers are comprised of repeat units derived from the monomer(s) that reacted to form the polymer.
• Understand the differences between biopolymers and synthetic polymers.
• Be able to name commonly encountered polymers.
• Be able to classify polymers as homopolymers or alternating, random, block, or graft copolymers.
• Be able to draw the mechanism of cationic, radical, and anionic addition polymerization reactions.
• Be able to draw the mechanism for common step-growth/condensation polymerization reactions.
• Be able to decide, based on monomer structure, which method (cationic or anionic) addition polymerization will be most effective.
• Be able to predict the products of condensation polymerization reactions.
• Working from polymer and byproduct structure, suggest reasonable monomeric starting material(s) for polymer synthesis.
• Explain the difference between chain-growth and step-growth polymerization and predict which one a monomer is likely to undergo.
• Be able to distinguish between branched and linear polymers and understand how branching affects polymer properties.
• Be able to classify vinyl polymers as syndiotactic, isotactic or atactic.
• Understand how the stereochemical configuration of polymers affects polymer properties.
• Understand how intermolecular forces and cross-linking affect polymer properties.
• Understand the properties of crystalline and amorphous polymers/regions.
• Know the definition of Tm and Tg.
• Know the difference in properties between thermoplastics, elastomers, fibers and thermosetting resins.
• Know common recycling codes, methods for polymer recycling and how polymer structure affects method of recycling.
• Be able to classify polymers as vinyl polymers, polyesters, polycarbonates, polyamides, polyethers or polyurethanes.
• Understand the differences between coordination-insertion polymerization and cationic, anionic and radical polymerization of alkene monomers.

## 27.1 Introduction to Synthetic Polymers

Chemistry instructors often point out that “chemistry is everywhere”; this is especially true when it comes to polymers. Much of your body is made of polymers, such as proteins and carbohydrates. The instructions for protein synthesis are encoded in polymers (DNA) and many of the chemical reactions essential to life are catalyzed by polymers (enzymes). All of the aforementioned are examples of biopolymers; these generally have precise lengths and functions, and are synthesized through cellular processes. On the other hand, synthetic polymers are, for the most part, prepared in laboratories and industrial plants using many of the basic organic reactions that you have already studied. Your clothes, car, water bottle, smartphone, house and food containers are constructed wholly, or in part, from polymeric materials; in most of the developed world, not a day goes by where a person does not benefit from synthetic polymers.

Polymers, or macromolecules, are constructed by linking many (102–105) smaller molecules (monomers) together via covalent bonds. For example, polyethylene (used to make plastic grocery bags and translucent plastic bottles) is prepared by polymerizing ethene monomers (Figure 27.1). Besides the fact that polymers are made from smaller molecules, the major, practical difference between polymer molecules and small molecules is in terms of their physical properties. Whereas most small organic molecules are gases, liquids, or brittle crystalline solids under ambient conditions, polymers are generally solids, with useful mechanical properties (e.g., strength, resistance to stretch) under the same conditions. This difference in behaviors is largely due to the greater surface area of polymer chains, which results in stronger intermolecular forces and entanglements between chains that make it difficult to separate the chains from one another (Figure 27.2).

## 27.2 Polymer Nomenclature

Polymer science is a relatively new area of chemical study. It is also unique in that it was developed largely in the industrial sector rather than in an academic setting. Because of these factors, the naming of polymers has two distinct conventions: one developed by industry and one developed by IUPAC. Having two systems of nomenclature can cause confusion for those new to the field of polymer chemistry, but since the industrial convention is the most commonly used, especially in North America, we will limit our discussion to this method.

### 27.2.1 Naming Vinyl Polymers

A polymer prepared from monomers that exchange their C=C double bond for a C–C single bond is called a vinyl polymer after the vinyl groups present in the monomers. Polyethylene (Figure 27.1) is an example of a vinyl polymer. More vinyl polymers are shown in Table 27.1. Notice that the name of these polymers comes from adding “poly” to the name of the monomer. Again, notice that some of the polymer names are derived from non-IUPAC names for the monomers. The parentheses in the figure represent a repeat unit of the polymer.

### 27.2.2 Naming Non-Vinyl Polymers

As we will see later in this chapter, vinyl polymers are prepared using different methods than those used for preparing polymers not derived from vinyl monomers. Naming non-vinyl polymers can be a bit more complicated than naming vinyl polymers since a greater variety of repeat unit structures are possible.

In some cases, the polymer is named after the monomer, as is the case for vinyl monomers (e.g., poly(ethylene glycol); Figure 27.3).

In some cases, the polymer is named after the repeat unit structure (e.g., poly(ethylene terephthalate); Figure 27.4).

Since the systematic IUPAC nomenclature is not often used for polymers, it is best to be familiar with the names for commonly encountered, non-vinyl polymers and to name new polymers using the analogy of the common examples summarized in Table 27.2.

Q27.1 - Level 1

What is the name of the polymer below?

A

Poly(1-pentene)

B

Poly(isopropyl butene)

C

Poly(1-hexene)

D

Poly(4-methyl-1-pentene)

Q27.2 - Level 1

What is the name of the polymer below?

A

Poly(ethylene glycol)

B

Poly(ethylene oxide)

C

Poly(propylene oxide)

D

Poly(propylene glycol)

Q27.3 - Level 1

What is the name of the polymer below?

A

Poly(methylene terephthalate)

B

Poly(terephthalic acid)

C

Poly(terephthalic ester)

D

Poly(propylene terephthalate)

## 27.3 Classification of Polymers

As discussed above, polymer chemistry was largely developed in industrial settings where the end use of the polymer is considered paramount. However, as the importance of polymeric materials to humanity became clearer, academic chemists adopted a systematic approach to the study of polymer chemistry. Whereas the industrial sector was primarily interested in polymers as commodity materials, academic chemists were more interested in understanding the fundamental mechanisms of polymer formation and behavior. As such, several different classification schemes have been developed; some based on polymer structures, some based on polymer properties and uses and some based on the mechanism by which a polymer forms.

### 27.3.1.1 Homopolymers and Copolymers

One of the simplest distinctions between polymer types is the distinction between homopolymers and copolymers. Homopolymers are prepared via the polymerization of only one monomer, whereas copolymers are prepared via the polymerization of two or more monomers (Figure 27.5).

Homopolymers can be further classified as being branched or linear. For example, depending on the conditions used to polymerize ethene, either branched or linear polyethylene may be formed (Figure 27.6). As we will see later, branched and linear polymers often have significantly different physical properties and end uses. In the case of polyethylene, the branched homopolymer is quite flexible and prone to stretching; thus, this material is used to make plastic grocery bags, whereas the linear homopolymer is used to make rigid plastic items like water bottles.

Copolymers can be further classified as random, alternating or block copolymers. As implied by the name, random copolymers result when two or more monomers are polymerized together and the monomeric subunits are randomly distributed throughout the polymer chain (Figure 27.5). Alternating copolymers result when two monomers are polymerized and the monomeric subunits alternate in a regular, repeating fashion. Block copolymers have extended sequences in which identical monomeric subunits are linked together (blocks).

For questions 27.4–27.7 below, the monomers are ethylene and propylene.

Q27.4 - Level 1

Classify the polymer below.

A

Homopolymer

B

Block copolymer

C

Alternating copolymer

D

Random copolymer

Q27.5 - Level 1

Classify the polymer below.

A

Homopolymer

B

Block copolymer

C

Alternating copolymer

D

Random copolymer

Q27.6 - Level 1

Classify the polymer below.

A

Homopolymer

B

Block copolymer

C

Alternating copolymer

D

Random copolymer

Q27.7 - Level 1

Classify the polymer below.

A

Homopolymer

B

Block copolymer

C

Alternating copolymer

D

Random copolymer

### 27.3.1.2.1 Vinyl Polymers

There are many common vinyl polymers, but these polymers can have a diverse set of functional groups and, hence, vastly different properties and uses.

Polymers derived from alkenes are often referred to as polyolefins (olefin is an archaic name for alkenes). Examples include polyethylene, polypropylene and polystyrene (Table 27.1). These polymers are composed only of carbon and hydrogen and, therefore, the primary intermolecular force acting between the polymer chains is the London dispersion force. Thus, these polymers are non-polar and hydrophobic and have effective barrier properties toward water. Polyolefins tend to be rigid, durable materials that resist degradation due to the strength of their C–C and C–H bonds; however, their properties can vary depending on the molecular weight of the polymer and stereochemical configuration about the polymer backbone. Generally speaking, low molecular weight polyolefins have poor mechanical properties because the strength of London dispersion forces depends on the surface area of a molecule; for example, polyethylene behaves like a waxy solid until it reaches a molecular weight of about 10,000 g/mol, whereas ultra-high molecular weight polyethylene (UHMWPE) is a very hard and durable material used in applications such as hip and knee replacements.

Haloalkenes can also be polymerized to form halogenated polyolefins. Two very common polymers in this class are polyvinyl chloride (PVC) and polytetrafluoroethylene (PTFE; TeflonTM) (Figure 27.7). PVC is a highly rigid material and most modern plumbing fixtures are made from this material. PVC may be made flexible by adding small molecules called plasticizers, which disrupt the regular packing of PVC chains. PTFE is commonly used as a non-stick coating on cookware since the high electronegativity of the fluorine atoms lead to low polarizability and, hence, weak London dispersion forces.

A third common class of vinyl polymers is the polyacrylates, which are derived from the polymerization of acrylic acid and its derivatives. Acrylic acid can be polymerized to form polyacrylic acid; this polymer can be deprotonated with NaOH to form sodium polyacrylate, which is extremely hydroscopic and is used as an absorbent material in disposable diapers (Figure 27.8). Other common polyacrylates and their uses may be found in Table 27.3.

### 27.3.1.2.2.1 Polyethers

Polyethers are made of repeat units containing C–O–C linkages. This very broad class of polymers has a diverse set of properties and applications ranging from adhesives to engineering plastics. Examples of commonly encountered polyethers may be found in Table 27.4.

### 27.3.1.2.2.2 Polyesters

Polyesters contain –C(=O)–O– linkages and, like polyethers, have a great diversity of structures and, hence, properties. The most commonly encountered polyester is poly(ethylene terephthalate) (PET), which is prepared via the reaction between ethylene glycol and terephthalic acid (Figure 27.9) and has been in use since the 1940s. Most soft drink bottles are made of PET. Another commonly encountered polyester is poly(lactic acid) (PLA), which has the benefit of being biodegradable and biorenewable; it may be found in certain food/drink containers and eating utensils and is marketed under the trade name GreenwareTM. Other commonly encountered polyesters and their uses are described in Table 27.5.

### 27.3.1.2.2.3 Polycarbonates

Polycarbonates have similar structures to polyesters except that they bear carbonate linkages (O–C(=O)–O–). The most commercially successful polycarbonate is called poly(bisphenol A carbonate) (BPA-PC); often simply called polycarbonate, it is prepared through the reaction of bisphenol A and phosgene (Figure 27.10). BPA-PC is marketed under the trade name LexanTM and owing to its high impact strength is used in applications such as bulletproof glass and safety helmets.

### 27.3.1.2.2.4 Polyamides

Polyamides bear amide linkages (–C(=O)–NH–) and are capable of hydrogen bonding. As a result of their ability to hydrogen bond, polyamides have very high tensile strengths (resist stretching) and have higher melting points than polyesters. The most commonly encountered polyamides are nylons, with nylon-6 and nylon-66 being the most prevalent (Figure 27.11). These polymers find uses mainly as fibers in applications from clothing to ropes. In fact, during World War II, when most of the silk in the United States was requisitioned to make parachutes for the military, stockings were manufactured from nylon and this polymer has displaced silk in many applications to this day due to its lower cost.

Another less common, but important polyamide is poly(p-phenylene terephthalamide) or KevlarTM (Figure 27.12). Because of the strong hydrogen bonding, rigid backbone structure, and π-stacking interactions between the benzene rings, the polymer chains in this polyamide pack quite closely and this results in a material of incredible strength and durability. Kevlar is used in lightweight bulletproof vests, in the construction of high performance automobile and bicycle tires and in numerous other applications where high strength and durability are important.

### 27.3.1.2.2.5 Polyurethanes

Polyurethanes are also sometimes called polycarbamates after the carbamic acid linkages they contain (–N(C=O)O–). Polyurethanes are typically synthesized via a reaction between diisocyanates and diols (Figure 27.13). They find use as insulators, upholstery, sponges and coatings. SpandexTM is another commonly encountered material containing a polyurethane. This polymer is actually a diblock copolymer with a flexible polyether segment and a rigid polyurethane segment (Figure 27.14). The combined properties of these two segments are responsible for Spandex’s ability to stretch without tearing.

Q27.8 - Level 1

Classify the following polymer according to its functional group.

A

Vinyl polymer

B

Polyether

C

Polyester

D

Polyamide

E

Polycarbonate

F

Polyurethane

Q27.9 - Level 1

Classify the following polymer according to its functional group.

A

Vinyl polymer

B

Polyether

C

Polyester

D

Polyamide

E

Polycarbonate

F

Polyurethane

Q27.10 - Level 1

Classify the following polymer according to its functional group.

A

Vinyl polymer

B

Polyether

C

Polyester

D

Polyamide

E

Polycarbonate

F

Polyurethane

Q27.11 - Level 1

Classify the following polymer according to its functional group.

A

Vinyl polymer

B

Polyether

C

Polyester

D

Polyamide

E

Polycarbonate

F

Polyurethane

### 27.3.1.3 Classification According to Polymer Formation Mechanism

There are two broad categories of polymer formation: chain growth or addition polymerization and step-growth or condensation polymerization (Figure 27.15). As the name implies, chain growth polymers form by sequential addition of monomer units to the end of a growing chain. In step-growth polymerization, small molecules combine randomly to form larger and larger molecules; these larger molecules can combine with each other to make even larger molecules and this process continues until the reactive end groups are capped. Step-growth polymerization is also referred to as condensation polymerization since, in many cases, a byproduct is formed, such as in the formation of poly(ethylene glycol) (PEG) where, along with the polymeric product, water is also formed (Figure 27.16).

### 27.3.1.3.1 Chain Growth (Addition) Polymerization

Chain growth polymerization is the most common method for the polymerization of vinyl monomers. There are four main types of addition polymerization mechanisms. Three of these (cationic, anionic, and radical) mechanisms you are already familiar with from previous chapters. The fourth mechanism, coordination–insertion polymerization, requires the use of a transition metal catalyst.

### Teflon

A famous polymer you have probably heard of is polytetrafluoroethylene (Teflon), which is found in wires, cables, and the coating on non-stick cooking pans.

The polymerization reaction used to synthesize polytetrafluoroethylene is a radical chain-growth polymerization.

Teflon can also be found on coated guitar strings, made by ELIXIR. These strings are used by many musicians!

### 27.3.1.3.1.2 Cationic Polymerization

Cationic polymerizations are mechanistically similar to the electrophilic addition reactions of alkenes that you saw earlier in this course. In a cationic polymerization an electrophilic initiator is used to react with the π-bond of the vinyl monomer. The resultant anion balances the positive charge of the carbocation formed during the initiation step to maintain electric neutrality. The carbocation then reacts with a monomer via electrophilic addition; this process is repeated over and over again as the polymer chain grows. Chain growth is terminated by adding an excess amount of a nucleophile that irreversibly reacts with the carbocation at the chain end (for example, water). Polyisobutylene (Figure 27.18) is one of the commercially important polymers that is formed via cationic polymerization and is used in adhesives, sealants, oils, and moisture barriers. Cationic polymerizations work most efficiently with monomers that bear electron-donating groups that can stabilize the electron-deficient carbocation; 1,1-disubstituted alkenes, with their electron-donating alkyl substituents, readily undergo cationic polymerizations as do vinyl ethers since their alkoxy groups can stabilize the carbocation via resonance (Figure 27.19).

Q27.12 - Level 2

Which monomer is most effectively polymerized via cationic polymerization?

Q27.13 - Level 2

Which monomer is most effectively polymerized via cationic polymerization?

Q27.14 - Level 2

Which monomer is most effectively polymerized via cationic polymerization?

### 27.3.1.3.1.3 Anionic Polymerization

Anionic polymerizations are initiated by nucleophilic attack on a vinyl monomer, much like that seen previously in the mechanism of the Michael addition. As a result of a nucleophilic attack, a carbanion is formed and attacks another vinyl monomer, thereby enchaining it and extending the growing polymer chain. Anionic polymerizations are terminated by the addition of an electrophile, like water or an acid. Because a carbanion is present at the growing chain end, monomers with electron-withdrawing groups (e.g., NO2, carboxyl, CN, and aromatics) are readily polymerized via anionic methods. Depending on the stability of the incipient carbanion, the nucleophile may be relatively weak like water or, in the case of a less stable carbanion, a stronger nucleophile like the butyl anion may be required to initiate polymerization. One of the most common polymers produced via an anionic mechanism is polycyanoacrylate or SuperGlueTM (Figure 27.20). Because of the electron-withdrawing cyano and methyl ester groups, the resulting carbanion is quite stable and the polymerization of cyanoacrylate can be initiated by atmospheric water; this is why SuperGlueTM containers must be tightly capped once opened.

27.15 - Level 2

Which monomer is most effectively polymerized via anionic polymerization?

Q27.16 - Level 2

Which monomer is most effectively polymerized via anionic polymerization?

Q27.17 - Level 2

Which monomer is most effectively polymerized via anionic polymerization?

Stuck on polymers? Here is another common one: super glue!

The major compound found in a bottle of super glue is called cyanoacrylate. Upon exposure to water vapor in the air, a polymerization reaction occurs to form a strong adhesive. Here is the mechanism for cyanoacrylate polymerization:

Step 1: Water attacks cyanoacrylate to form a nucleophilic enolate.

Step 2: The enolate attacks another cyanoacrylate molecule to form the ‘polymerization intermediate’.

Step 3: This process is repeated until all the cyanoacrylate is consumed to give the polymer.

### Keeping it Real Q27.1

Keeping it Real Q27.1 - Level 2

Using the image above, predict the structure of the ‘polymerization intermediate’.

A

a

B

b

C

c

Polycyanoacrylate is nicely featured in the 2014 hit film "The Lego Movie". In this masterpiece, a construction worker Emmet tries to stop Lord Business’ evil plan to glue the Lego universe together with the ‘Kragle’ (aka Krazy Glue). Does Emmet stop Lord Business’ plan? You’ll have to watch the movie to find out!

### 27.3.1.3.1.4 Coordination–Insertion Polymerization

In the 1950s, Karl Ziegler and Giulio Natta discovered that certain transition metal compounds (commonly group 4 or group 10 metals) were capable of catalyzing the polymerization of alkenes with high levels of control over chain length and, in the case of 1-alkenes, stereochemical configuration of the pendent groups of the polymer backbone. For their discovery, the pair were awarded the 1963 Nobel Prize in chemistry. The mechanistic details of Ziegler–Natta catalysis are quite complex compared with the other chain growth mechanisms described above and require a solid background in organometallic chemistry to fully comprehend. The basic mechanism is shown in Figure 27.21. The first step, coordination, involves the donation of the π-electrons from the alkene into an empty orbital of d-parentage of the transition metal. The second step, migratory insertion, involves the nucleophilic attack of a coordinated metal alkyl group at the more substituted carbon of the coordinated alkene; in this process, a new C–C σ bond is formed and a new M–C σ bond is formed while the C=C π-bond is broken and the original M–C σ bond is broken. After the migratory insertion step, a new vacant site is created and another alkene monomer can bind to the metal; thus, the process is repeated as the polymer chain grows. The steric environment around the metal center determines the stereochemical outcome of the coordination and insertion thereby controlling the stereochemical configuration of the pendent groups on the polymer backbone. Natta’s original catalyst system comprised of TiCl4- and AlMe3-produced isotactic polypropylene, where the pendent methyl groups were all oriented on the same side of the polymer backbone (see Figure 27.34). Recent advances in catalyst architecture have provided access to syndiotactic poly(alphaolefins). Atactic poly(alphaolefins) can be prepared with certain non-stereoselective catalysts or via radical polymerization. The tacticity of polymers plays a major role in determining their properties as we shall see in a later section.

### 27.3.1.3.2 Step-Growth (Condensation) Polymerization

The mechanisms of step-growth polymerization are almost as varied as the mechanisms for all of the reactions you have encountered in your study of organic chemistry since most organic reactions that are used to prepare step-growth polymers are energetically favorable (negative ΔG). We will focus on common methods for the formation of the five most frequently encountered non-vinyl polymers mentioned previously: polyethers, polyesters, polycarbonates, polyamides, and polyurethanes.

### 27.3.1.3.2.1 Polyethers

Polyethers can be formed by self-condensation reactions of diols; however, in some cases, the competing formation of cyclic ethers complicates the process. For example, treating 1,2-ethanediol with a catalytic amount of acid results in the preferential formation of 1,4-dioxane rather than polyethylene glycol (Figure 27.22). If the monomer structure is chosen carefully so as to avoid the formation of cyclic ethers, then self-condensation reactions can result in polymerization as is the case when 1,4-benzenedimethanol is allowed to react in the presence of an acid catalyst (Figure 27.23).

### 27.3.1.3.2.2 Polyesters

Polyesters can be formed by many of the methods you have already seen for the preparation of small molecule esters including direct esterification, trans-esterification, and the reaction of a diol with a diacid chloride or acid anhydride. The most common polyester (PET) is formed via direct esterification between 1,2-ethanediol and terephthalic acid as seen in Figure 27.24.

### 27.3.1.3.2.3 Polycarbonates

Polycarbonates are often formed via a reaction between phosgene and a diol. For example, BPA-PC is formed via the nucleophilic addition reaction between bisphenol A and phosgene (Figure 27.25).

### 27.3.1.3.2.4 Polyamides

Like polyesters and polycarbonates, the formation of polyamides depends on the nucleophilic attack on a carbonyl carbon. For example, nylon 6,6 can be prepared via reaction between 1,6-hexanediamine and adipoyl chloride (Figure 27.26).

### 27.3.1.3.2.5 Polyurethanes

Polyurethanes can be formed via the reaction of bischloroformates with diamines (Figure 27.27), but this method has the disadvantage of producing hydrogen chloride as a byproduct. From an industrial, economic, and environmental standpoint, the production of this corrosive byproduct is quite costly. An economic method for producing polyurethanes is via the reaction of diisocyanates with diols (Figure 27.28); in this case, no byproducts are formed.

Q27.18 - Level 2

What is the byproduct of the following polymerization reaction?

A

H$_2$O

B

HCl

C

No byproduct

D

CO$_2$

E

O$_2$

Q27.19 - Level 2

What is the byproduct of the following polymerization reaction?

A

H$_2$O

B

HCl

C

No byproduct

D

OCl$_2$

E

Cl$_2$CO

Q27.20 - Level 2

What is the byproduct of the following polymerization reaction?

A

H$_2$O

B

HCl

C

No byproduct

D

NCO

E

(NH$_2$)CO

Q27.21 - Level 2

What is the byproduct of the following polymerization reaction?

A

H$_2$O

B

HCl

C

No byproduct

D

CH$_4$

E