Chapter 2 Review, pages 110 115 Knowledge 1. (c) 2. (b) 3. (c) 4. (a) 5. (a) 6. (c) 7. (d) 8. (c) 9. (d) 10. (d) 11. (a) 12. (d) 13. (a) 14. (a) 15. (c) 16. (a) 17. (a) 18. False. Polymers are large, chain-like molecules built from small molecules called monomers. 19. True 20. True 21. False. Most plastics are chemically unreactive and virtually indestructible. 22. True 23. True 24. False. Polyamides are polymers formed by condensation reactions resulting in amide linkages between monomers. 25. False. Examples of natural polymers are carbohydrates, silk, and DNA. 26. (a) (iii) (b) (vi) (c) (xi) (d) (vii) (e) (i) (f) (ix) (g) (ii) (h) (x) (i) (v) (j) (viii) (k) (iv) 27. A polymer is a very large molecule that is built from monomers. 28. A homopolymer is a polymer formed by reactions involving a single type of monomer. A copolymer has different types of monomers combined to form the polymer chain. 29. (a) The compound shown in Figure 1 is 3-bromo-3-chloroprop-1-ene. Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-2
(b) 30. Monomers that permit the formation of cross linkages between polymer chains increase the rigidity of the polymer. 31. Answers may vary. Sample answer: Polymer Example of use polyvinyl chloride water pipes polystyrene building insulation HDPE milk jugs, bottles LDPE plastic bags 32. (a) The monomer of Teflon is tetrafluoroethene: F 2 C=CF 2. (b) The strong C F bonds are very resistant to chemical change, which makes Teflon useful for applications such as electrical insulation, non-stick coatings, and low-friction surface coatings. 33. (a) Phthalates are added as plasticizers to make rigid polymers more flexible. (b) Health Canada has banned the use of some phthalates in children s products. 34. (a) A copolymer is a polymer that consists of more than one type of monomer. (b) The production of nylon involves a condensation polymerization. (c) (d) Amide bonds form between monomers during the reaction. 35. (a) Nomex is the product of a condensation reaction. (b) The by-product is hydrogen chloride. (c) 36. Dacron is a polyester because the monomers are connected by ester linkages. 37. Water is a common by-product of condensation polymerization. 38. Amide linkages are formed by reactions between amines and carboxylic acids. 39. The structure of the polymer formed by oxirane monomers is: CH 2 CH 2 O CH 2 CH 2 O 40. Answers may vary. Sample answer: Carothers developed nylon, which was designed to replace silk. Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-3
41. (a) A monosaccharide is a ketone or aldehyde with many additional hydroxyl substituents. (b) A polysaccharide is a large polymer consisting of many monosaccharide units. (c) A carbohydrate is a monosaccharide or a disaccharide. 42. (a) Glycogen is produced by animals to store energy. (b) Cellulose is produced by plants to provide structure. (c) DNA is produced by many organisms to pass on genetic information. 43. The cellulose-rich parts of food plants are often used as animal food because certain animals, such as cattle, can digest it. 44. (a) A protein is a polymer built by condensation reactions between amino acids. (b) A peptide bond is an amide linkage between 2 amino acids. (c) DNA is a polymer that stores and transmits genetic information. 45. (a) Nucleotides consist of a 5-carbon sugar, a nitrogen-containing organic base, and a phosphoric acid molecule. (b) Nucleotides are esters. (c) Cytosine and guanine are held together by hydrogen bonds. (d) These nucleotides contain carbonyl and amine groups, which can form hydrogen bonds. Understanding 46. Answers may vary. Sample answer: An organic chemist may want to determine the chemical structure of spider silk to come up with a synthetic version, the production of which can be controlled. 47. Answers may vary. Sample answer: 48. Natural polymers are expensive and can be problematic to access. There is a limit to how much can be produced within a given time. 49. The addition of sulfur creates cross-links between rubber polymers, causing rubber to become more rigid at high temperatures. Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-4
50. Answers will vary. Sample answer: (a) name polyethene polypropene polystyrene (b) monomer (c) polymer (d) plastic bags carpet fibres building insulation common use 51. (a) Identify the repeating unit. Replace a single bond between carbons with a double bond. (b) Identify the repeating unit. Replace a single bond between carbons with a double bond. (c) Identify the repeating unit. Replace a single bond between carbons with a double bond. 52. The addition of divinylbenzene makes polystyrene more rigid by allowing cross-links to form between adjacent polymer chains. 53. (a) Plasticizers are additives that increase the flexibility of brittle synthetic polymers. (b) Phthalates, which are effective plasticizers, have been linked to severe negative health effects, such as kidney and liver failure. They may also disrupt the human reproductive system, especially as a result of childhood exposure. Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-5
54. (a) A polymer produced during an addition reaction consists of a chain of carbon atoms bonded with single bonds. A condensation polymer contains oxygen or nitrogen atoms between carbon atoms in the main chain, which indicate the presence of ester or amide linkages, respectively. (b) To predict the monomer from an addition polymer, (i) determine the repeating units, and (ii) determine which two carbon atoms in the monomer share a double bond so that all carbon atoms in the monomer form four bonds. (c) To predict the monomer from a condensation polymer, (i) determine the repeating units; (ii) if a nitrogen atom is part of the main carbon chain in the polymer which indicates that one or both monomers has an amine functional group add an H to complete the amine group and add an OH group to complete a different functional group (carboxyl or hydroxyl); and (iii) if an oxygen atom is part of the main carbon chain in the polymer which indicates that the monomers have hydroxyl and/or carboxyl groups add an OH group to complete the carboxyl group and an H to complete the hydroxyl group. 55. (a) The polymer that forms from pent-2-ene is an addition polymer. (b) The polymer that forms from1,5-diaminopentane and propane-1,3-diol is a condensation polymer and a polyamide. (c) The polymer that forms from 1,5-dichlorohex-2-ene is an addition polymer and a polyester. 56. Similarities Differences Addition polymers Condensation polymers made up of carbon chains natural and synthetic no functional groups at have a functional group the ends of the carbon at one or both ends of the chain carbon chain formed by breaking of small molecules (e.g., double bonds between water) produced as byproducts monomers no small molecules most natural polymers produced as by-products Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-6
57. (a) The structure of polylactic acid is: (b) Water is formed. (c) Hydrogen bonds would form between PLA chains. (d) The plastic should be flexible and non-toxic to make it suitable for food packaging. 58. Answers may vary. Sample answer. Polyesters Polyamides Similarities -condensation polymers -water produced as by-product - copolymers -natural and synthetic Differences -one monomer has a hydroxyl group and the other has a carboxyl group -formed by esterification reactions (have ester linkages) -produce H 2 O(l) as a byproduct -one monomer has an amino group while the other has a carboxyl group or an acid chloride group -monomers bind together with amide linkages -produce H 2 O(l) or HCl(aq) as a by-product 59. (a) Answers will vary. Sample answer: Synthetic polymers are inexpensive to mass-produce and are very versatile. They can be made into a wide variety of products that are ubiquitous in our daily lives. This makes them very useful. (b) Since synthetic polymers are used so widely and are so inexpensive to produce, there are huge quantities of them around. Synthetic polymers break down very slowly; so their disposal is a major problem. In addition, some of them are hormone disruptors and carcinogens. 60. (a) This sugar is an aldehyde. (b) A condensation reaction occurs to form the ring structure. (c) 61. (a) A molecule of hexose contains 6 carbon atoms. (b) A monosaccharide with 5 carbon atoms is called pentose. Analysis and Application 62. Answers may vary. Sample answer: (a) A plastic used to wrap food should be flexible, transparent, and non-toxic. (b) A plastic used to build the International Space Station should be lightweight yet durable and also somewhat flexible so it does not shatter when it collides with space debris. Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-7
(c) There are many different types of plastics with different properties because many different types of monomers can be combined and processed in a variety of ways. 63. Thermoplastics melt or soften when heated, hold their shape when cooled, and can be molded. They do not contain many cross-links. Thermoset polymers are highly crosslinked, so they do not soften at high temperatures. Based on these differences, thermoplastics would be easier to recycle because they can be processed more easily for new uses. 64. (a) (i) (ii) (b) Polymer (ii) would have more hydrogen bonding between its chains because bonds would form between hydrogen and oxygen and nitrogen atoms on adjacent chains. These additional linkages between chains would make the polymer more heat stable. 65. (a) Condensation polymers could be made biodegradable by making them using naturally occurring monomers. If the monomers are naturally occurring, there is likely a natural process that spontaneously decomposes these monomers and hopefully decomposes the polymers they form as well. (b) Problems that could still occur despite the biodegradability of these plastics are toxicity and contamination. If the smaller chains or monomers are toxic, smaller pieces could spread more easily, poisoning humans, wildlife, and the environment. The bacteria used to digest the fragments may also pose a health hazard, especially if they are not contained. 66. Curls in hair are caused by disulfide bonds. Straight hair can be made curly by adding a product to it that causes the formation of disulfide bonds within hair strands, and then twisting the hair around rods while the bonds form. 67. More heat is needed to break G C pairs because they are held together by 3 hydrogen bonds, as opposed to 2 hydrogen bonds between the A T pairs. 68. (a) Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-8
(b) The monomer of starch is glucose. (c) When you eat a plain unsalted cracker, at first it tastes bland. After chewing for a short time, it starts to taste sweet. This effect is evidence that saliva is breaking the starch down into its component glucose, a simple sugar. Evaluation 69. (a) The monomer for the polymer in Figure 9 (a): The monomer for the polymer in Figure 9 (b): (b) Polymer (b) is more rigid because it consists of straight-chain molecules that are tightly packed. The rigidity of this polymer would make it appropriate for use as structural material. 70. Answers will vary. Sample answer: In my opinion, it is more important that plastics be durable and long lasting. That way, they can be more easily reused for longer time periods, which would decrease the need to manufacture replacement plastics. Fewer plastics would then need to be discarded. 71. Butan-1,4-diol should be used because it can form a copolymer with benzene-1,2-dicarboxylic acid. Using propan-1-ol will not result in a polymer because propan-1-ol has only one hydroxyl group. This prevents propan-1-ol from reacting with more than one acid molecule and extending the chain. 72. Answer may vary. Sample answer: (a) Six possible factors to consider include cost of research and development, production cost, cost of raw materials, demand for product, profit margin, and environmental impact of product. (b) The company might rank the importance of these factors in the following order: profit margin, demand for product, cost of research and development, production cost, cost of raw materials, environmental impact of product. (c) I would rank the importance of these factors as follows: environmental impact of product, demand for product, cost of research and development, production cost, cost of raw materials, and profit margin. Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-9
(d) I am concerned about the environment, and so the environmental impact and the need (demand) for the product are most important for me. For a company that needs to stay in business and keep people employed, profit margin and production cost would be the most important considerations. Reflect on Your Learning 73. Answers will vary. Sample answer: Before studying this chapter, I was aware that there were natural as well as synthetic polymers, but I didn t know what exactly a polymer was, nor did I know there were so many different kinds of polymers. 74. Answers will vary. Sample answer: After reading this chapter, I am much more aware of the importance of recycling plastics. Because so much plastic is discarded and because plastics don t break down easily, I think it is very important to prioritize research and development of biodegradable plastics. This way, we won t run out of room in landfill sites as quickly. Research 75. Answers may vary. Sample answer: Carpet recycling is a complex and expensive process. First, an old carpet is scanned for its polymer content: nylon or polypropene. These polymers are then separated. The long top fibres are shaved off and spun into recycled yarn. The remaining nylon content is sold to other companies to be used as nylon plastic for landscaping products, auto parts, and roof shingles. Cradle-to-cradle carpet recycling programs are very rare in Canada. Most are located in the United States. In the Greater Toronto Area, there is a carpet recycling facility in Markham: Sands Commercial Floor Coverings. 76. Answers will vary but could include the following: a polymer used as an anode in lithium-ion batteries, which could extend the distance electric cars could travel and reduce their cost a polymer for flooring made from rapidly renewable plant materials, which would decrease reliance on fossil fuels for raw materials Russian doll polymer vesicles (vesicles within vesicles) in nanomedicine, which could deliver several different drugs or active ingredients in a single vesicle a polymer that captures nicotine molecules to determine nicotine content of materials in biomedical and industrial applications 77. Answers may vary. Sample answer: Poly(glycolic acid) (PGA) and poly(lactic acid) (PLA) are biodegradable polyesters that break down in the body by way of hydrolysis of the ester linkage. The products of hydrolysis are non-toxic and non-harmful, and are excreted by the kidneys or eliminated as carbon dioxide and water. The polymers are currently being used as resorbable implants and surgical sutures. Researchers are looking for ways to use these polyesters to encapsulate and deliver drugs. 78. Answers may vary. Sample answer: To make fabric from milk protein, liquid milk is dried and its proteins are extracted. The separated milk proteins are dissolved in a chemical solution. Once they are dissolved, they are placed into a machine that whirls the proteins into fibres. The fibres are then ready for spinning into yarn and weaving into fabric. Fabric made from milk can be dyed. Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-10
The cloth is breathable and traps moisture; so skin feels smooth and tender, just as after bathing in milk. On the down side, the fabric is easily wrinkled after being washed and requires ironing. Clothing made from milk fabric needs to be washed by hand. Given this information about milk fabric, I would wear milk fabric garments for the novelty of the experience, but would not buy them if they were expensive. 79. Answers may vary. Sample answer: I don t think it is worthwhile to research artificial skin for the sake of making it bulletproof. However, it would be useful to research artificial skin for medical uses, such as for burn victims. 80. Answers will vary but could include the following: - Vitamin A is needed for reforming rhodopsin, a compound on the retina that is needed for vision in low light - night blindness is an early sign of vitamin A deficiency - vitamin A deficiency can dry out the cornea, causing it to become clouded - corneal dryness can progress to corneal ulcers - severe deficiency can cause retinal damage, leading to blindness Copyright 2012 Nelson Education Ltd. Chapter 2: Polymers 2-11