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Chapter 20

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  1. Chapter 20 Organic Chemistry

  2. Students will learn about… • Carbon bonding • Saturated vs. unsaturated • Isomerism – normal vs. branched • Groups of organic compounds – alkanes, alkenes, alkynes, alcohols, ethers, esters, ketones, aldehydes, aromatic compounds, carboxylic acids, amines, amides • Naming organic compounds • Reactions of organic compounds • Polymerization

  3. Organic Compounds • Organic compounds – vast majority of C and H compounds • Also called hydrocarbon compounds • natural gas, gasoline, heating oil, plastic, jet fuel, asphalt • May contain O (alcohols, aldehydes, ketones, carboxlyic acids), N (amines and amides), and S (thio-) • Carbon is unusual • Bonds strongly to itself • Forms long chains or rings

  4. Carbon Bonding • A carbon atom bonds with 4 atoms • the simplest hydrocarbon compound • tetrahedral shape • bond angle = 109.5° • saturated • Double bond • sharing 4 electrons • unsaturated • Triple bond • sharing 6 electrons • unsaturated

  5. Alkanes • C and H only • All single bonds • Saturated • C2H2n+2 (Ex) CH4 (n = 1); C2H6 (n = 2); C3H8 (n = 3) • The names end with “-ane” (Ex) methane, ethane, propane, butane

  6. Normal, Straight-chain, or Unbranched Hydrocarbons • Contain strings or chains of carbon atoms • Can be represented by the structure m = a whole number

  7. First Ten Straight-Chain Alkanes

  8. Structural Isomerism • Molecules with the same atoms but different arrangement • Butane and all succeeding members of the alkanes exhibit structural isomerism.

  9. Isomers of Pentane

  10. Alkyl Substituents • alkyl • Adjective term based on alkane • One hydrogen atom is missing from an alkane (Ex) methane vs. methyl

  11. Common Alkyl Substituents

  12. Rules for Naming Alkanes • Find the longest continuous chain (= parent chain) of carbon atoms. • Number the carbons in the parent chain, starting at the end closest to any branching (the first alkyl substituent). • Name for each alkyl group, indicating its position on the parent chain with a number. CH3 | CH3–CH2–CH–CH2–CH2–CH3 1 2 3 4 5 6 3-methylhexane

  13. When alkyl group occurs more than once, attach the appropriate prefix (di– for two, tri– for three, and so on) to the alkyl name. • The alkyl groups are listed in alphabetical order, disregarding any prefix. CH3 CH3 | | CH3–CH2–CH–CH–CH2–CH3 1 2 3 4 5 6 3,4-dimethylhexane

  14. Examples Name each of the following: a) b)

  15. Reactions of Alkanes • Combustion Reactions (Ex) • Substitution Reactions: primarily where halogen atoms replace hydrogen atoms. (Ex)

  16. Dehydrogenation Reactions: Hydrogen atoms are removed and the product is an unsaturated hydrocarbon. (Ex)

  17. Alkenes & Alkynes • Alkenes: contain a carbon–carbon double bond. [CnH2n] CH3CH=CH2propene • Alkynes:contain a carbon–carbon triple bond. [CnH2n – 2] CH3CH2C≡CCH3 2–pentyne

  18. Rules for Naming Alkenes 1. Root hydrocarbon name ends in –ene. C2H4 is ethene 2. With more than 3 carbons, double bond is indicated by the lowest–numbered carbon atom in the bond. CH2=CHCH2CH3 1 2 3 4 1–butene

  19. Rules for Naming Alkynes • Same as for alkenes except use –yne as suffix. CH3CH2C≡CCH2CH2CH2CH3 3–octyne

  20. Exercises Name each of the following: a) 2,3,5-trimethyl-2-hexene b) 6-ethyl-3-methyl-3-octene

  21. Addition Reactions • New atoms form single bonds to the carbons formerly involved in a double or triple bond. • Hydrogenation– use H2 as the reactant to be added • Halogenation– addition of halogen atoms

  22. Aromatic Hydrocarbons • Cyclic unsaturated hydrocarbons with strong aromas. • Benzene – simplest aromatic hydrocarbon = =

  23. Monosubstituted Benzenes

  24. Disubstituted Benzenes

  25. Functional Groups *amides: on the next slide

  26. Amides

  27. Polymerization • Large chainlike molecules made from many small molecules called monomers. • Simplest polymer – polyethylene • Polyethylene results from addition polymerization.

  28. Condensation Polymerization • A small molecule (often water) is released for each addition of a monomer to the polymer chain. • Nylon • Copolymer – 2 different types of monomers combine to form the chain