CHEM219/CHEM 219 Module 8 – Principles of Organic Chemistry with Lab | Portage Learning | Updated

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CHEM219/ CHEM 219 Module 8 – Principles of Organic Chemistry with Lab | Portage Learning | Updated 2026–2027 | Complete Questions & Verified Answers ... | Grade A 2026 / 2027 Academic Year Q: Polymer Answer large molecule made by repetitive linking of smaller units (monomers) Q: Macromolecule Answer very large molecule composed of thousands of covalently bonded atoms (ex: polymer) Q: two ways polymers are made Answer 1. natural (in nature) 2. synthetic (in lab) Q: examples of natural polymers Answer rubber, carbs: starch & cellulose, proteins, nucleic acids DNA, RNA Q: examples of synthetic polymers Answer nylon, teflon, styrofoam, polyethylene, Dacron, Q: 3 main ways to differentiate polymers Answer 1. method of formation 2. final composition 3. stereochemical orientation Q: Two types of Synthetic polymers Answer 1. chain-growth 2. step-growth Q: chain growth polymers are also know as: Answer addition polymers Q: How are chain growth polymers made? Answer made by addition of one monomer unit to another in a repetitive pattern Q: chain growth polymerization Answer A polymerization involving sequential addition to monomers that are unsaturated (C=C) or have some other reactive functional groups (particularly ethylene and derivatives) Q: what 2 things stops chain growth polymerization? Answer 1. intervention 2. consumption of all available monomers Q: Teflon Answer chain-growth polymer: polytetrafluoroethylene monomer: F2C=CF2 nonstick coating, goretex, electrical insulator, chem-resistant coating Q: Saran Answer chain-growth polymer: polyvinylidenedichloride monomer: H2C=CCl2 cling-wrap Q: Polypropylene Answer chain-growth polymer: polypropylene monomer: H2C=CHCH3 carpet fibers, car parts, toys, packaging, houseware Q: Orlon, Acrilan, Creslan Answer chain-growth polymer: polyacrylonitrile monomer: H2C=CH(CN) textiles/fibers, carpets, upholstery Q: Polyvinyl Acetate Answer chain-growth polymer: polyvinyl acetate monomer: H2C=CH(OCOCH3) elmers glue, silly putty, latex paints Q: Polyvinyl alcohol Answer chain-growth polymer: polyvinyl alcohol monomer: H2C=CH(OH) eye med- artificial tears Q: Plexiglass (Lucite) Answer chain-growth polymer: polymethylmethacrylate monomer: H2C=C9CH3)COOCH3 clear plastic sheets , blocks, and tubing Q: the final polymer retains all of the atoms of the monomer Answer the final polymer retains all of the atoms of the monomer Q: step growth polymerization Answer formed by the reaction between 2 different functional groups on different monomer molecules with the accompanying loss of some small molecule (typically water) Q: The defining characteristic of step-growth polymers Answer The final polymer chain does NOT include all the atoms initially present in the monomer molecules Q: step-growth polymers also known as: Answer condensation polymers Q: functionality of step-growth monomers Answer typically di or polyfunctional Q: appearance of monomers in step-growth polymerization Answer alternating order in the final polymer chain Q: how step-growth polymers generally grow Answer by carbon-heteroatom bond formation Q: how chain-growth polymers generally grow Answer carbon-carbon bond formation Q: Polyamide (Nylon) Answer formed by combining 1,6-diaminohexane (amine) with 1,6-hexandioic acid (carboxylic acid) amine functionality reacts with carboxylic acid functionality to form an amide with a corresponding loss of a water molecule naturally occurring step-growth/ condensation polymer examples Answer cellulose, polypetide chains, beta-Hydroxybutyric acid Lexan Answer step-growth polymer: polycarbonate eye glasses, auto parts, drinking glasses Kevlar Answer step-growth polymer: polyamide body armor, tires, helmets step-growth polymer: polyester Dacron, Mylar Answer eletric/thermal insulation, helium balloons, artificial limbs three main mechanisms for addition/ chain-growth polymerization Answer 1. free radical 2. cationic 3. anionic For all three main addition mechanisms, how does polymerization begin? Answer (initiation) begins by creating a reactive intermediate that starts the chain reaction free-radical addition polymerization Answer a monomer reacts with a free-radical initiator to create a free-radical free-radical Answer an atom or a group of atoms that has one unpaired electron radical initiator Answer a reagent that creates radicals, has relatively weak covalent bonds which can be homolyzed 3 main characteristics of free-radicals Answer 1. electrically neutral 2. quite reactive and reacts quickly to pair up the lone electron 3. formed from radical initiators Homolyzed bond Answer broken so that each atom joined by the bond gets one of the two electrons in the bond benzoyl peroxide Answer example of a radical initiator (o-o bond = weak and can undergo homolysis upon heat or UV exposure to produce 2 benzoyl radicals) how much initiator is needed in polymerization and does any remain at the end of the reactions? Answer only a small amount of radical initiator is needed compared to the concentration of monomers present -some remains in final product but it does not affect the product two main things that control polymer properties Answer 1. the monomer used 2. the molecular weight of the final polymer chain what happens after the radical initiator has formed radicals? Answer radical can attack + homolyze C=C of monomer to create a reactive intermediate that starts polymerization which substituent does the radical add to in the monomer? Answer adds to the LEAST substituted carbon of the C=C bond because this carbon is easier to approach and less hindered to produce a more stable radical intermediate What happens during propagation of free-radical polymerization? Answer produces a new radical that can continue the polymerization chain reaction: Each attack of the radical with a new monomer unit extends the chain by one unit what is chain propagation the same as? Answer some step as initiation in that monomers add in head to tail fashion with substituents present on alternating carbons in the chain What 4 main factors determine the extent of the polymerization? 1. temperature 2. pressure 3. solvent used 4. monomer concentration speed of free radical chain growth Answer extremely rapid- can grow by thousands of monomers in less than a second Termination of free-radical polymerization Answer stops the chain growth, involves 2 radical species- pairing of 2 unpaired electrons and formation of new covalent bond 2 pathways of termination Answer 1. Radical Coupling 2. Radical Disproportionation Radical Coupling termination of free-radical polymerization where 2 radicals combine using the unpaired electrons on each to make a new covalent bond monomer arrangement in radical coupling head-to-head arrangement, substituents are attached to adjacent carbons radical disproportionation One radical abstracts a hydrogen atom from another radical species which forms a new covalent bond and makes and alkane- then an alkene is formed by the combination of unpaired electrons on adjacent carbons Radical Coupling AND radical disproportionation form what type of species from radical species? both form non-radical species from radical species which stops the growth of the polymer chain 3 steps in a Chain Reaction of free-radical polymerization 1. Initiation 2. Propagation 3. Termination Initiation of Free Radicals production of a radical species from a non-radical species using heat or UV light Propagation of Free Radicals reaction of a radical with a non-radical producing a new radical species and continuing the chain reaction what is chain transfer dependent on? Rates of the straight chain propagation steps versus the chain transfer steps -Rates are controlled by stability of the intermediate radicals that form as a product in each Termination of Free Radicals reaction of 2 radicals with each other producing a non-radical- no intermediate reactive = reaction stops chain transfer reaction type of propagation step where a radical in one polymer chain abstracts a hydrogen atom from a position in a different polymer chain which causes branching in a growing polymer chain Cation Chain-Growth Polymerization best for substrates that can form stable carbocation intermediates (typically unsubstituted substrates like bulky alkenes or alkenes with electron-donating substituents) How is cation addition polymerization initiated? By adding a strong acid to an alkene to form a carbocation intermediate cation addition polymerization propagation carbocation intermediate + new alkene monomer molecule adds one unit to the polymer chain each time cation addition polymerization termination terminates by the removal of a hydrogen atom from a carbon atom adjacent to the positively charged carbon to form an alkene (like in an elimination reaction) main catalysts used for anionic addition polymerization Grignard Reagents (R: -[MgBr]+) Alkyllithium (R:-Li+) Anionic addition polymerization a form of chain-growth polymerization or addition polymerization that involves the polymerization of monomers initiated with anions. The type of reaction has many manifestations, but traditionally vinyl monomers are used. Why use anionic addition polymerization useful for alkenes with electron-withdrawing substituents such as cyano groups, phenyls, esters anionic addition polymerization propagation chain grows by 1 anionic intermediate adding to the C=C bond of a monomer molecule. monomer anion adds in place of a Grignard Reagent or Alkyllithium reagent. each addition grows by one unit anionic addition polymerization termination accomplished by quenching reaction with a proton source such as water or alcohol what is formed when a monosubstituted alkene monomer is polymerized? a new chiral center is formed at every position where the substituent branches from the back bone of the chain Tacticity describes the location in the polymer chain of chiral centers rather than using R or S designation 3 main classes of polymer tacticity 1. Atactic 2. Isotactic 3.Syndiotactic atactic stereocenters have random configurations Isotactic all stereocenters have the same configuration syndiotactic Stereocenters alternate in configuration atactic configuration is labeled as Stereorandom isotactic and syndiotactic are labeled as Stereoregular How does having different tacticity with the same monomer effect the monomer? The same monomers with different tacticity will have different physical properties EX: atactic polypropylene (soft matrix adhesive) vs isotactic polypropylene (high-melting solid that can be molded or machined) 2 ways to control polymer stereochemistry 1. chain-end control 2. site control preferential formation of chain-end control -1st chiral center that forms will determine all subsequent stereochemistry in the polymer -an existing chiral center will force an incoming group to one side of the molecule Chain end control at an existing stereocenter and the end of the chain, the next monomer will be influenced by how the chiral center projects into space Site Control The specific shape of the reagent or catalyst that facilitates the reaction also determines the stereochemistry. Ziegler-Natta catalyst most famous site control to prod stereoregular polymers. uses various transition metal catalysts to control sites where monomers are added to the chain Ligands A molecule that binds specifically to a receptor site of another molecule. -coordinated to the metal ion that bind monomers prior to insertion into the growing chain -specifically utilized in Ziegler-Natta catalysts what 2 factors of ligands orient monomers into position shape and size hold monomers into position in ONE orientation what two types of polymers can Ziegler-Natta catalysts be used on? Isotactic and Syndiotactic (only stereoregular polymers) Homopolymer a polymer made up of one type of repeating unit. It is made from one monomer only. Copolymer polymers composed of more than one type of monomer -used to control properties of a polymer product (like flexibility or chemical resistance) Random (Statistical) Copolymer monomeric units distributed randomly and unevenly in the chain Alternating Copolymer monomeric units distributed regularly + alternating with nearly equimolar amounts in each chain Block Copolymer long sequence/ blocks of one monomer is joined to a block of the second monomer Graft Copolymer side chains of a given monomer are attached to main chains of a second monomer biggest causative agent of the exact sequence in copolymer chains: relative reactivity of the monomers present situation creates what copolymer? A reacts rapidly with B but slow with self B reacts rapidly with A but slow with self alternating sequence (ABABABABABA) two things that determine the reactivity of a monomer 1. number of substituents present 2. type of substituents present situation creates what copolymer? A and B are equally reactive towards each other and self random sequence (ABBAAAAABABBBAABBBBBBBAABABBB) situation creates what copolymer? One monomer in in copolymer is more reactive than other to all species mixture of two different homopolymers situation creates what copolymer? polymerization of monomer A is iniated, then B is added, then A is added, etc -particularly useful for anionic polymerization bc the living end (anion) stays active until the reaction is quenched. Block sequence situation creates what copolymer? first polymerize a monomer with additional functionality (a second double bond) in its structure -makes a polymer with multiple bonds -homopolymer is formed -monomer B added with a radical initiator to graft section of B onto reactive sites of A. Graft sequence polymer properties are strongly affected by: 1. molecular weight (and distribution) 2. amount of branching (of the chain architecture) how do long branches affect crystallinity? undergo side-chain crystallization (able to form rows of crystals on their own) how do short branches affect crystallinity? Reduce crystallinity (interfere with the formation of crystals) Amorphous polymers polymer chains arranged in random manner- not regularly aligned as in a crystal important example of an amorphous polymer polystyrene (monomer styrene ((Vinyl Benzene))) thermoplastic softens upon heating and hardens upon cooling (property of polystyrene) what is produced by adding a low boiling inert solvent like pentane to the polymerization reaction of polystyrene where the pentane boils off into gas and the volatilization causes bubbles that expand the polymer into a foam. Styrofoam What allows amorphous polymers to be made more rigid/ crystalline (and thus less amorphous) Cross-Linking Cross-linking definition small amounts of polyfunctional monomers are added to form links (covalent bonds between growing chains) these links tether the growing chains together in a less random, more crystalline order characteristics of cross-linked polystyrene more rigid, less soluble in organic solvents than native what are the main properties that characterization techniques of polymers seek to discover? molecular mass, molecular structure, morphology, thermal properties, mechanical properties molecular mass of polymers differs from typical molecules d/t polymerization reaction producing a distribution of molecular weights and shapes molecular mass of polymers = average molecular weight and polydispersity Polydisperity (PD) how heterogenous the range of particle size is Spectroscopy: UV-visible, infrared, Ramen, Nuclear magnetic resonance, electron spin resonance, xray diffraction, mass spectrometry techniques used to characterize polymers by identifying common function groups + other structure features (also used to determine molecular structure of unknown molecules) an atom has gained or lost electrons ion a characteristic of atom that varies regularly across the periodic table periodic property a compound held together by a shared pair of valence electrons covalent compound a compound formed by ions ionic compound the electrons that exist farthest from the atom's nucleus and generally have the highest energy level number valence electrons most atoms strive to attain eight valence electrons octet rule an indicator of an atom's size atomic radius the amount of energy needed in order to take an electron away from an atom ionization potential a measure of how strongly an atom attracts extra electros to itself a electronegativity the process by which an atom turns into an ion by gaining or losing electrons ionization

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