1. Chapter 9. ORGANIC CEMISTRY Most kown chemical compounds are carbon-containing organic compounds with carbon atoms in straight chains, branched chains, or rings (Figure 9.1) Figure 9.2. The molecular geometry of organic chemicals is an important characteristic

2. 9.2. HYDROCARBONS (Figure 9.3) Alkanes are hydrocarbons in which the carbon atoms are joined by single bonds consisting of two shared electrons Alkenes have at least one double bond between C atoms Alkynes have at least one triple bond between C atoms Aromatic (aryl) hydrocarbons have characteristic ring structures, usually consisting of 6 C atoms (benzene ring)

3. Figure 9.4. Structural formulas of four alkanes each containing 8 C atoms

4. Formulas of Alkanes A molecular formula, such as C 8 H 18, may apply to a number of different alkanes containing 8 C atoms (Figure 9.4) Isomers in straight chains, branched chains, and rings Isomers are shown by structural formulas Alkanes and alkyl groups (examples below):

5. Names of Alkanes and Organic Nomenclature Systematic names from which the structures of organic molecules can be deduced (see examples below) Common names without structural implications 1. Based on longest continuous chain of C atoms 2. Longest chain is numbered from one end 3. Substituent groups by number of carbon attached and by name 4. Prefixes to denote multiple substitutions Example: 2,2,3-Trimethylpentane

6. Reactions of Alkanes Combustion (example of burning propane fuel) C 3 H 8 + 5O 2  3CO 2 + 4H 2 O Substitution reactions, such as those used to make organohalides CH 4 + Cl 2  CH 3 Cl + HCl

7. Alkenes and Alkynes Alkenes have at least one double bond consisting of 4 electrons shared between carbon atoms Simplest alkene is ethylene (ethene) Ethene is a very important industrial chemical produced in large quantities for the manufacture of polyethylene plastic and other chemical products 1,3-Butadiene (Figure 9.3) is widely used to make synthetic rubber Alkynes have a triple bond (6 shared electrons) between C atoms Acetylene, C 2 H 2, Figure 9.3, is the simplest alkyne Acetylene is widely used in welding

8. Addition Reactions of Alkenes and Alkynes Alkenes and alkynes are unsaturated hydrocarbons because they have additional electrons available for bonding in their double and triple bonds Unsaturated bonds enable addition reactions

9. Alkenes and Cis-trans Isomerism Since rotation cannot occur around a double bond, cis and trans isomers are possible as shown in figure 9.5

10. Condensed Structural Formulas The structural formula of 3-ethyl-4-methylhexane (below) can be represented by the condensed structural formula CH 3 CH 2 CH(C 2 H 5 )CH(CH 3 )CH 2 CH 3

11. Figure 9.6. Representation of Structural Formulas with Lines

12. Aromatic (Aryl) Hydrocarbons and Aromatic (Aryl) Compounds Figure 9.7. Representation of benzene, an aromatic compound Aromaticity Aromatic compounds have ring structures Particularly stable bonds that contain delocalized clouds of  (“pie”) electrons (resonance stabilization) Low hydrogen/carbon ratio Tend to undergo substitution reactions characteristic of alkanes rather than addition reactions characteristic of alkenes C atom bonded with 1 H atom

13. Figure 9.8. Some Aromatic Compounds

14. Polycyclic Aromatic Hydrocarbons Condensed ring systems typified by benzo(a)pyrene, Figure 9.8 Carbon-rich hydrocarbons Formed by preferential combustion of hydrogen in hydrocarbons under oxygen-deficient conditions Sources include engine exhausts, wood stove smoke, cigarette smoke, and charbroiled food Some, notably benzo(a)pyrene, are metabolized to carcinogens

15. Type of group Example Group formula Table 9.2. Important Functional Groups Characterized by Specific Groupings of Atoms

16. Figure 9.9. Examples of Oxygen-Containing Organic Compounds

17. Figure 9.10. Example Organonitrogen Compounds Methylamine is a bad-smelling, toxic, basic compound Dimethylnitrosamine is a carcinogen 2,4,6-Trinitrotoluene is a high explosive Organonitrogen compounds include herbicides, insecticides, many other kinds of substances

18. Trisodium Nitrilotriacetate (NTA), an Organonitrogen Compound that is a Strong Metal Chelating Agent

19. Figure 9.11. Some Important Organohalide Compounds

20. Figure 9.12. Halogenated Naphthalenes and Biphenyls PCBs are important, persistent water pollutants

21. Chlorofluorocarbons, Halons, and Hydrogen-Containing Chlorofluorocarbons Chlorofluorocarbons (CFCs) are volatile low-molecular-mass compounds in which Cl and F are bonded to carbon Were widely used as refrigerants, foam blowing, in aerosol sprays Now phased out because of destruction of stratospheric ozone Halons are organobromine compounds Fire retardents Harmful to stratospheric ozone Hydrohalocarbons are H-containing chlorofluorocarbons or fluorocarbons that substitute for CFCs More reactive H-C bonds in hydrohalocarbons enable their destruction at low altitudes so that they do not reach the stratosphere where they could affect stratospheric ozone

22. Chlorinated Phenols Pentachlorophenol has been a significant hazardous waste material and water pollutant until it was banned

23. Figure 9.13. Some Organosulfur Compounds Thiols Methanethiol 2-Propene-1-thiol 1-Butanethiol Benzenethiol Sulfides and Cyclic Sulfides Thiourea Compounds Thiourea Thiophene (an unsat- urated sulfide) Thiophane Organic derivatives of thiourea (R is a hydrocarbon group 1-Naphthyl- thiourea (ANTU) Dimethyl sulfide

24. Figure 9.13 (Cont.) Sulfoxides and Sulfones Sulfonic Acids and Salts Dimethylsulfoxide (DMSO) Sulfolane Benzenesulfonic acidSodium 4-decylbenzenesulfonate Methyl sulfateEthyl sulfate Organosulfate Esters

25. Figure 9.14. Organophosphorus Compounds

26. 9.4. SYNTHETIC POLYMERS The synthetic polymers industry is huge with important implications for sustainability, materials, and the environment Polymers are formed by the joining together of small molecules called monomers Many natural products are polymers, such as cellulose in wood or cotton, a polymer of glucose sugar Polymers are the basis of many industries, such as rubber, plastics, and textile manufacture

27. Figure 9.15. Formation of Polyvinylchloride Polymer Polyvinylchloride is used in a wide variety of applications including PVC pipe manufacture

28. Figure 9.16. Monomers in Widely Used Polymers Polyethylene (plastic bags, milk cartons) Polypropylene (impact-resistant plastics, indoor-outdoor carpets) Polyacrylonitrile (Orlon, carpets) Polystyrene (foam insulation) Polytetrafluoroethylene (Teflon coatings, bearings)

29. Figure 9.17. Polymeric Cation Exchanger

30. Sustainability and Environmental Implications of Polymers Monomers pose environmental and safety hazards Volatile, combustible, explosive polymers, such as ethylene Combustion of polymers can produce noxious products, such as HCl from combustion of polyvinylchloride Plasticizers used in polymers may cause environmental problems Phthalate plasticizers are environmentally persistent, resistant to treatment processes and prone to undergo bioaccumulation

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