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York University
CHEM 3050

CH. 9 & 10 CHEMISTRY STUDY GUIDE EXAM 3 CH305 Exam 3 Things to know: Chapter 9&10 only. A few ideas from the last exam may carry through, and some concepts from CH304K of course. Again, this might not cover absolutely everything, but it gives you a good starting point. Know all the functional groups given in Ch 9 AND in Ch.10. Be able to spot them in a structure. Chapter 9: The World of Polymers and Plastics -POLYMERS are everywhere! are NATURAL and SYNTHETIC are made from non-renewable and (now sometimes) renewable materials -Most polymers (CDs, DVDs, plastic case around cell phone/pencil, calculator, computer) come from a single raw material: petroleum (main feedstock for polymers) - Petroleum: non-renewable resource 3% of petroleum is used as a raw material (some of this is for pharmaceuticals) -“Big Six” all made from petroleum -Polymers can be made from any carbon-containing starting material (crude oil) -Renewable resources to form polymers: materials such as wood, cotton fibers, straw, starch and sugar -Cargill Dow: “Nature Work PLA” from corn glucose -DuPont: “Sonora”-family of polymers from corn based substances Polymers: large molecules containing a long chain or chains of atoms covalently bonded together; can contain 1000s of atoms -referred to as macromolecules: molecules of high molecular mass that have characteristic properties b/c of their large size -Monomers: (mono- “one” meros- “unit”) small molecules used to synthesize the larger polymeric chain -polymers can be formed from the same type of monomer or from a combination What is a Plastic?: “capable of being molded” (used as a noun or adjective) PLASTICS are SYNTHETIC polymers. Other materials may have plastic properties (metals). NOTALL POLYMERS are PLASTICS! Some polymers occur naturally. Adding Up the Monomers : -Covalent chemical bonds connect the monomers -polymer contains exactly the same number and kinds of atoms as did the monomers -Addition polymerization: the monomers add to the growing polymer chain in such a way that the product contains all the atoms of the starting material. No other products are formed Polyethylene: found in plastic milk jugs, detergent containers, baggies, and packaging materials; has wide variety of uses but all are made from the same starting material : H2C = CH2 -Dispersion forces: the intermolecular attractive forces holding polyethylene together; attr- actions between molecules that result from a distortion of the electron cloud that causes an uneven distribution of the negative charge -Astrategy to control the molecular structure and physical properties of polymers is to regulate the branching of the polymer chain ; used to produce high-density polyethylene (HDPE) and low-density polyethylene (LDPE) -LDPE: stretchy, transparent, not very strong; central polymer chain has many side branches -HDPE: linear (unbranched) polyethylene chains consisting of 10,000 monomer units; long chains can arrange more parallel w/o the branching; more crystalline than the irregular tangle of the polymer chains in LDPE; GREATER DENSITY, RIGIDITY, STRENGTH, and a HIGHER MELTING POINT than LDPE; OPAQUE SEE WRITTEN NOTES ON POLYETHYLENE & THE BIG SIX!! “The Big Six”: over 60,000 synthetic polymers are known; 6 synthetic polymers account for 75% of those used in the U.S.; “THE BIG SIX” 1. Polyethylene (LDPE) -soft, flexible, unreactive -plastic bags, bubble wrap, electrical insulation, ‘dispenser’type bottles 2. Polyethylene (HDPE) -stiffer than LDPE -stiff plastic bags, milk jugs 3. Polypropylene (PP) -rigid, strong, shiny, impermeable -battery cases, carpets, bottle caps 4. Polystyrene (PS) -very clear, rigid, dissolves in many solvents -Styrofoam insulation..AND drinking glasses 5. Polyvinyl chloride (PVC) -rigid, strong, resists solvents and oils: used for pipe, siding, credit cards -PLASTICIZER added to make it flexible for hose, shower curtains 6. Polyethylene terephthalate (PET) -TWO different monomers -transparent, strong, impervious to gases -soda bottles, clear food containers, fleece fabrics, carpet yarns, beverage glasses -Don’t all use different monomers! ;ALL are COLORLESS; all are INSOLUABLE in WATER, however so dissolve/soften in the presence of hydrocarbons, fats, and oils THERMALPROPERTIES -All 6 polymers are thermoplastic: with heat they can be melted and reshaped over and over again VS. thermosetting: CANNOT be re-melted and shaped PHYSICALPROPERTIES Some parts of the same polymer have varying degrees of toughness and strength -crystalline regions: the long polymer molecules are arranged neatly and tightly in a regular pattern; very orderly and repeating pattern; make polymers rigid and strong -dominant in HDPE, PP - plasticizers: disrupt crystallinity, making a polymer more flexible -amorphous regions: the long polymer molecules are found in a random, disordered arrangement and their packing is much looser; make polymers flexible -dominant in PET, PS, PVC ADDITION POLYMERS: Polyethylene (HDPE, LDPE), Polyvinyl chloride (PVC), Polypropylene (PP), Polystyrene (PS) CONDENSING THE MONOMERS Functional groups: common groups of atoms different monomers contain; distinctive arrangements of groups of atoms that impart characteristic chemical properties to the molecules that contain them -Hydroxyl -carboxylic acid -ester -amine -amide -phenyl condensation polymerization: process in which the monomers join by eliminating (splitting out) a small molecule such as water -TWO PRODUCTS: the polymer itself & molecules released during the polymer’s formation -AMINOACIDS/PROTEINS, NYLON, PET/PETE copolymer: a combination of two of more different monomers -POLYETHYLENE TEREPHTHALATE (PET) : made of ethylene glycol & terephthalic acid -POLYAMIDES: NATURALAND NYLON -Two other classes of polymers 1. Proteins (natural polymers) 2. Nylon (synthetic substitute) amino acids: the monomers from which our body builds proteins; each amino acid molecule contains two functional groups: an amine group (-NH2) and a carboxylic acid group (-COOH) -20 different amino acids occur naturally polyamides: PROTEINS/NYLON are polyamides: condensation polymers that contain the amide functional group peptide bond: the covalent bond that forms when the –COOH group of one amino acid reacts with the –NH2 group of another, thus joined the two amino acids. RECYLCING: THE BIG PICTURE Municipal solid water (MSW): includes everything you discard or throw into your trash including food scraps, grass clippings, and old appliances. MSW does not include industrial waste or waste from construction sites. Disposal of Plastics : Most of our plastic ends up in a landfill! Alternatives: Incineration Biodegradation Reuse Recycle Reduction Incineration of Plastics Your Turn 9.22 Per pound contains more energy than coal! Does generat2 CO and may also generate HCl, phosgene (COC2) and leave ash with heavy metals Resulting ash however is a MUCH smaller volume - and metals can be extracted from it, if profitable. Biodegradation Consider This 9.19, 9.21 Big Six not broken down by bacteria. Biodegradable versions being developed but questions continue about how well they degrade and the toxity of the degradation products. These 'compostable plastics' (see Fig 9.15) must be composted done under the right conditions. EVEN NATURALLY OCCURRING polymers do NOT break down in landfills! See Fig 9.16. This is due to the anaerobic (oxygen-free) conditions that exist in landfills. “Paper vs Plastic” (Consider This 9.26) Volume is the biggest problem: 11% of landfill trash is plastic, 35%, paper. (by mass: see Fig 9.14) Plastic bags take up less room than paper! (See Fig 9.21 page 417) RECYCLING PLASTICS: THE DETAILS Recycling Plastics ALL of the Big Six, can be theory BUT: Unlike aluminium, more energy is used than in synthesizing new! The idea is to reduce the dependency on fossil fuels. See Fig 9.17, 9.18, 9.19 and Table 9.3: The US is recycling more of everything now than in the past.. but the overall percent of plastics recycled in the US is DROPPING!! We recycle more each year... but EVEN more is being manufactured! Bottle bills are a way to encourage compliance.. but are hotly debated. Why Recycling Plastic is not always done: Must be a good alternative to virgin plastic: Consistent availability requires reliable collection facilities. Consistent purity requires thoroughly sortingAND cleaning . Price of crude oil also affects demand.. cheap crude means cheaper virgin plastic. Often ends up as flowerpots or plastic lumber – downgraded. (Consider This 9.28, 9.29) Recycling “Success”: PET (1) bottles can become polyester fabrics: fleece, carpeting, tops of running shoes LPDE (4) grocery bags – return to store, becomes more bags Reduce, Reuse, Recycle: RECYCLED - CONTENT: has recycled materials IN it. Two kinds: PRECONSUMER CONTENT: Recycled materials are from manufacturing process (scraps, trimmings - i.e., 'cleaner' - easier for the manufacturer to do) POSTCONSUMER CONTENT: Recycled materials are those which would have ended up in the trash - industrial or consumer - this is the best one!! "RECYCLABLE" DOES NOT MEAN THE SAME THING as the above statements!!! Look for “% post consumer waste” on label. Consumers must create demand for products made with it!!! Alternative Plastics Recycling DuPont has developed a process to break PET back into monomers!! Reuse / Reduce Examples: Styrofoam Peanuts: donate to smaller shipping stores (call first and ask!) Many bottles / food containers are now made with less plastic - look for these. Avoid excessively packaged products. Which two of the BIG SIX are the same monomer? Polyethylene (LDPE) & Polyethylene (HDPE) Chapter 10:MANIPULATING MOLECULES & DESIGNING DRUGS -Prescription Drugs, Over the Counter (OTC) Drugs, Herbal Alternatives, Illicit Drugs andAbused Prescription Drugs -Early Drugs; Folk remedies, Discovered by trial and error, Passed on by word of mouth (China, India, Egypt, Rome/Greece) -Willow Bark Tea (ASPIRIN) : Folk remedy - known in several cultures Reduced fevers (ANTIPYRETIC), inflammation (ANTI-INFLAMMATORY) and pain: (ANALGESIC) - 4th century B.C. : Hippocrates documents “willow bark tea” - 1763: Edmund Stone (England) investigates willow tree bark (Salix alba) - reports to Royal Society. Active ingredient isolated from willow bark tea: - two compounds were found, only one was effective. o The active one which became an acid in the body was named salicin. Salicin was synthesized and used.. with SIDE EFFECTS! It tastes terrible, and can cause stomach irritation. -Felix Hoffman's father took salicin for his arthritis - got nauseous. In 1898 (while a chemist at Bayer), Hoffman modified salicin: -reacted the alcohol part with acetic acid: made an ESTER. -The salicin still had another acid group: so the end result was called acetylsalicylic acid : or ASPIRIN ESTER part: lessened effect of the remaining acid group so: tasted better; irritated stomach less BUT.. in body, this splits back into salicin and acetic acid - works just as well as salicin! STILL has side effects: (drowsiness, rash/hives/itch, nausea/vomiting/abdominal pain, heartburn, black/bloody vomit, jaundice, shortness of breath)
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