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Hewitt/Lyons/Suchocki/Yeh Conceptual Integrated Science Chapter 14 ORGANIC CHEMISTRY Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley This lecture will help you understand: • • • • • • • Organic Chemistry Hydrocarbons Unsaturated Hydrocarbons Functional Groups Alcohols, Phenols, Ethers, and Amines Ketones, Aldehydes, Amides, Carboxylic Acids, and Esters Polymers Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Organic Chemistry A branch of chemistry involving the study of carbon-containing chemical compounds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Organic Chemistry Organic Compound: A carbon containing chemical compound 100,000 new ones each year natural Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley synthetic Organic Chemistry Why is carbon so special? Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Organic Chemistry Why is carbon so special? • Carbon atoms connect with one another through strong and stable covalent bonds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Organic Chemistry C C C C N C N N C N N N O O O O O S O Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley S S S S Organic Chemistry C C 347 kJ/mol C C C N N N C N N N O O O O O S O Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley S S S S Organic Chemistry C C 347 kJ/mol C C C N N 159 kJ/mol N N C N N O O O O O S O Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley S S S S Organic Chemistry C C 347 kJ/mol C C C N N 159 kJ/mol N N C N N O O O O O O S 138 kJ/mol Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley S S S S Organic Chemistry C C 347 kJ/mol C C C N N 159 kJ/mol N N C N O O O O N O O S 138 kJ/mol Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley S S S 226 kJ/mol S Organic Chemistry S S S S S S S Sulfur, S8 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley S Organic Chemistry S S S S S S S S Sulfur, S8 More atoms of the same element bound together like this is rare… Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Organic Chemistry S S S S S S S S Sulfur, S8 More atoms of the same element bound together like this is rare… …for every element except carbon…. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Organic Chemistry Why is carbon so special? • Carbon atoms connect with one another through strong and stable covalent bonds. • Carbon atoms also readily form bonds with many other types of atoms. This provides for a near infinite number of different kinds of organic compounds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Organic Chemistry To appreciate organic chemistry, please minimize memorization… Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Hydrocarbon: A chemical compound containing only hydrogen and carbon. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Structural isomer: Molecules having the same molecular formula but different structures. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Structural isomer: Molecules having the same molecular formula but different structures. “configurations” Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Structural isomer: Molecules having the same molecular formula but different configurations. Configuration: The specific way in which the atoms of a molecule are connected to one another. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Structural isomer: Molecules having the same molecular formula but different configurations. Configuration: The specific way in which the atoms of a molecule are connected to one another. “Configuration” = “Connectivity” Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Formula Number of possible isomers C5H12 3 C6H14 5 C7H16 9 C8H18 18 C10H22 75 C20H42 366,319 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Conformation: The spatial orientation of a single configuration. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Conformation: The spatial orientation of a single configuration. Rotate this bond Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Conformation: The spatial orientation of a single configuration. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Conformation: The spatial orientation of a single configuration. Like pivoting your arm at the elbow Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons Conformation: The spatial orientation of a single configuration. These are two “conformations” of the same configuration. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons CHECK YOUR NEIGHBOR What is the chemical formula for the following structure? A. B. C. D. C3H8 C4H10 C5H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? A. B. C. D. C3H8 C4H10 C5H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? c c c c A. B. C. D. C3H8 C4H10 C5H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley c Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? H H H H c c H H c H H A. B. C. D. c H c H C3H8 C4H10 C5H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley H H Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? H H H H c c H H c H H A. B. C. D. c H c H C3H8 C4H10 C5H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley H H Hydrocarbons Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Carbon always forms four bonds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Carbon always forms four bonds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Carbon always forms four bonds. Some of these bonds, however, may be within multiple bonds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Carbon always forms four bonds. Some of these bonds, however, may be within multiple bonds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Unsaturated Hydrocarbon: A hydrocarbon containing one or more multiple bonds. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Unsaturated Hydrocarbon: A hydrocarbon containing one or more multiple bonds. A special case of an unsaturated hydrocarbon is the benzene ring. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Unsaturated Hydrocarbon: A hydrocarbon containing one or more multiple bonds. A special case of an unsaturated hydrocarbon is the benzene ring. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons Unsaturated Hydrocarbon: A hydrocarbon containing one or more multiple bonds. A special case of an unsaturated hydrocarbon is the benzene ring. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons CHECK YOUR NEIGHBOR What is the chemical formula for the following structure? A. B. C. D. C5H10 C5H12 C6H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? A. B. C. D. C5H10 C5H12 C6H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? c c A. B. C. D. c c c C5H10 C5H12 C6H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Unsaturated Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? H H H c c H H c H A. B. C. D. c H c H C5H10 C5H12 C6H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley H H Unsaturated Hydrocarbons CHECK YOUR ANSWER What is the chemical formula for the following structure? H H H c c H H c H A. B. C. D. c H c H C5H10 C5H12 C6H12 C6H14 Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley H H Functional Groups Heteroatom: Any atom other than hydrogen or carbon in an organic molecule. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Functional Groups Heteroatom: Any atom other than hydrogen or carbon in an organic molecule. Functional Group: A combination of carbon, hydrogen, and heteroatoms that behave as a single unit. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Functional Groups Heteroatom: Any atom other than hydrogen or carbon in an organic molecule. Functional Group: A combination of carbon, hydrogen, and heteroatoms that behave as a single unit. Organic molecules are classified by the functional groups they contain. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Functional Groups Heteroatom: Any atom other than hydrogen or carbon in an organic molecule. Functional Group: A combination of carbon, hydrogen, and heteroatoms that behave as a single unit. Organic molecules are classified by the functional groups they contain. For example… Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Functional Groups Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Alcohols, Phenols, Ethers, and Amines Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Alcohols Contain the Hydroxyl Group Hydroxyl Group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Methanol (bp 65°C) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Ethanol (bp 78°C) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley 2-Propanol (bp 97°C) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols Contain the Phenol Group Phenol Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic H+ Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic H+ Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic H+ Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phenols are acidic Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley 4-n-Hexylresorcinol Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Thymol Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Ethers contain an oxygen bonded to two carbons Ether Group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Dimethyl ether (bp −25°C) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Dimethyl ether (bp −25°C) Ethanol bp 78°C Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Diethyl ether Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Amines form alkaline solutions Amine Group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Ethyl amine Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Hydroxide ion Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phosphoric acid Caffeine Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Caffeine salt Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phosphoric acid Caffeine salt Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Phosphoric Water soluble acid Alcohols, Phenols, and Amines CHECK YOUR NEIGHBOR Which of the following compounds should have a higher boiling point? O N H Structure A A. B. C. D. Structure A Structure B Both the same No way to tell Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Structure B Alcohols, Phenols, and Amines CHECK YOUR ANSWER Which of the following compounds should have a higher boiling point? O N H Structure A A. B. C. D. Structure A Structure B Both the same No way to tell Structure B Explanation: Structure B has a hydrogen attached to a strongly electronegative atom, nitrogen. This makes for a polar N—H bond that participates in hydrogen bonding. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Carbonyl A carbon atom double bonded to an oxygen atom Carbonyl Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Ketone Group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Ketone Group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Aldehyde Group Acetone Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Acetone Acetaldehyde Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Acetone Formaldehyde Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Citral Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Cinnamonaldehyde Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Benzaldehyde Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Vanillin Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Amide Group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley N,N-Diethyl-m-toluamide DEET Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Carboxyl group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Salicylic acid Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Aspirin Acetylsalicylic acid Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Ester group Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Salicylic acid Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley CH3OH H2SO4 Salicylic acid Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Methyl salicylate (Wintergreen) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Penicillin Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Functional Groups CHECK YOUR NEIGHBOR The amino acid lysine is shown below. What functional group must be removed in order to produce the very smelly amine cadaverine, which is 1,5-pentanediamine? A. The hydrogen (shown) must be removed and replaced with an amino (NH2) group. B. Lysine is 1,5-pentanediamine. Nothing has to be removed. C. The carboxyl group must be removed and replaced with a hydrogen. D. One amino group must be removed and replaced with a hydrogen. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Lysine Functional Groups CHECK YOUR ANSWER The amino acid lysine is shown below. What functional group must be removed in order to produce the very smelly amine cadaverine, which is 1,5-pentanediamine? A. The hydrogen (shown) must be removed and replaced with an amino (NH2) group. B. Lysine is 1,5-pentanediamine. Nothing has to be removed. C. The carboxyl group must be removed and replaced with a hydrogen. D. One amino group must be removed and replaced with a hydrogen. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Lysine Functional Groups CHECK YOUR NEIGHBOR In which of the following structures is carbon bonded five times? A. B. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley C. D. Functional Groups CHECK YOUR ANSWER In which of the following structures is carbon bonded five times? A. B. C. Explanation: Carbon can never be bonded five times! In none of the above structures is carbon indicated to be bonded five times. Sorry for the trick question… Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley D. Functional Groups CHECK YOUR NEIGHBOR In which of the following structures is carbon bonded five times? A. B. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley C. D. Functional Groups CHECK YOUR ANSWER In which of the following structures is carbon bonded five times? A. B. C. Explanation: Carbon can never be bonded five times! Structure C, therefore, is NOT a plausible structure for any existing organic compound. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley D. Polymers Polymer: A very long organic molecule made by the joining together of smaller organic molecule units known as monomers. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers Monomer Monomer Monomer Monomer Polymer: A very long organic molecule made by the joining together of smaller organic molecule units known as monomers. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H C C H H H H C C H Ethylene H Ethylene Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H C C H H H H C C H Ethylene H Ethylene Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H C C H H H H C C H Ethylene H Ethylene Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H C H H H C C H H Ethylene C H Ethylene Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H C H H H C H Ethylene H C H C H Ethylene Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H H H C C C C H H H H Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H H H H H C C C C C C C C C C H H H H H H H H H H H H H H Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H H H H H C C C C C C C C C C H H H H H H H H H H H H H H Addition Polymer: A polymer whose mass is equal to the sum of the masses of the monomer units. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers H H H H H H H H H H H H C C C C C C C C C C C C H H H H H H H H H H H H Ethylene Ethylene Ethylene Ethylene Polyethylene Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Ethylene Ethylene Polymers H H C C H CH3 Propylene Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley H H H C C CH3 Propylene Polymers H H H H H H H H H H H H C C C C C C C C C C C C H CH3 H CH3 H CH3 H CH3 H CH3 H CH3 Propylene Propylene Propylene Propylene Propylene Polypropylene Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Propylene Polymers Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers Condensation Polymer: A polymer formed when the joining of monomer units is accompanied by the loss of a small molecule, such as water. Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers CONSIDER THIS… Many of the natural product molecules synthesized by plants are formed by the joining together of isoprene monomers via an addition polymerization. A good example is the flavoring molecule citral, which is made of two isoprene units. Find and circle these units within the structure shown to the right. Isoprene (2-methyl-1,3-butadiene) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Citral Polymers CHECK YOUR ANSWER Many of the natural product molecules synthesized by plants are formed by the joining together of isoprene monomers via an addition polymerization. A good example is the flavoring molecule citral, which is made of two isoprene units. Find and circle these units within the structure shown to the right. Isoprene (2-methyl-1,3-butadiene) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Citral Polymers CONSIDER THIS… Beta-carotene is a natural addition polymer made of eight isoprene units. Find and circle these units within the structure shown below. Beta-carotene Isoprene (2-methyl-1,3-butadiene) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley Polymers CHECK YOUR ANSWER Beta-carotene is a natural addition polymer made of eight isoprene units. Find and circle these units within the structure shown below. Beta-carotene Isoprene (2-methyl-1,3-butadiene) Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison Wesley