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Ch. 11: Unsaturated Hydrocarbons

Ch. 11: Unsaturated Hydrocarbons. Chem 20 El Camino College. Unsaturated Hydrocarbons. Unsaturated means that the molecule contains one or more multiple bonds Alkenes contain a double bond Alkynes contain a triple bond. Label as alkane, alkene, or alkyne. alkane. alkene. alkene. alkyne.

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Ch. 11: Unsaturated Hydrocarbons

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  1. Ch. 11: Unsaturated Hydrocarbons Chem 20 El Camino College

  2. Unsaturated Hydrocarbons • Unsaturated means that the molecule contains one or more multiple bonds • Alkenes contain a double bond • Alkynes contain a triple bond

  3. Label as alkane, alkene, or alkyne alkane alkene alkene alkyne

  4. Naming • Name the longest carbon chain that contains the multiple bond (-ene or –yne) • Number the chain to give the multiple bond the lowest number, show location • Give the location and name of each substituent in alphabetical order, using numbers, hyphens, and commas between numbers • Give location of the double bond (if needed)

  5. Name These propene 2-butene 1-butene 2-butyne

  6. Name These 2-methylpropene 4,4-dibromo-1-butyne 3-bromo-3-chloro-1-butene

  7. Draw These 1-chloro-1,2,2-trifluoroethene 1,2-dimethyl-1-cyclohexene 1,1,4,4-tetrabromo-2-pentyne

  8. Cis-Trans Isomers • cis--on the same side of the double bond • trans--on opposite sides of the double bond • The cis and trans isomers are different molecules and have different properties • cis-2-butene bp = 3.7 oC • trans-2-butene bp = 0.3 oC

  9. Cis-Trans Isomers • The groups that are cis and trans may differ • cis & trans do not refer to gps on the same C • The words cis and trans come first in the names, followed by a hyphen

  10. Write the names 1-pentene 4-chloro-1-pentene trans-3-heptene cis-1-bromo-1-butene

  11. Write the names cis-3,4-dibromo-3-hexene trans-3,4-dibromo-3-hexene trans-4,4,6,6-tetrabromo-2-hexene

  12. Addition Reactions • In addition reactions of alkenes, the double bond breaks and two atoms add to the molecule • We’ll study some addition reactions • Addition of H2 (hydrogenation) • Addition of X2 (halogenation) • Addition of H2O (hydration)

  13. Hydrogenation • In hydrogenation reactions of alkenes, the double bond breaks & 2 H atoms add • A catalyst such as Pt, Ni, or Pd speeds up the reactions • A cmpd with a multiple bond is unsaturated • A cmpd with single bonds only is saturated

  14. Hydrogenation • Double bonds react with 1 molecule of H2 • Triple bonds react with 2 molecules of H2

  15. Write Product, Name Reactant & Product cyclopentene cyclopentane trans-4-methyl-2-pentene 2-methylpentane

  16. Halogenation Double bond reacts with 1 molecule of bromine Addition of bromine is useful for detection of carbon-carbon double bond

  17. Bromination One cyclohexene molecule reacts with 1 molecule of bromine to give 1,2-dibromo cyclohexane Rapid decolorization of a bromine solution is characteristic of compound containing carbon-carbon double bond

  18. Hydration • In hydration reaction of alkene, the double bond breaks, H and OH add with formation of an alcohol • An acid catalyst (shown as H+) is used • If the two “C”s of the double bond are attached to different groups, H adds to the carbon of the double bond with more “H”s.

  19. Hydration

  20. Write Product, Name Reactant, C6H12O cyclohexene C5H12O 2-methyl-2-butene

  21. 3-D (Spatial) Drawings • Bonds lying on the plane of the paper are shown with ordinary lines • Bonds coming out of the page are shown as solid wedges • Bonds going to the back of the page are shown as dashed (striped, broken)wedges

  22. 3-D (Spatial) Drawings • Note--every tetrahedral will have two lines, one broken wedge(dash), and one solid wedge. The lines make the zig-zag chain.

  23. 3-D (Spatial) Drawings • Draw a spatial drawing for butane • Draw a spatial drawing for 2,2-dibromopropane

  24. 3-D (Spatial) Drawings • Do not show planar atoms with dashes or wedges • Draw a spatial drawing for trans-1-bromo-1-propene

  25. Aromatic Hydrocarbon • Benzene molecule, C6 H6 , consists of a ring of six carbon atoms with one hydrogen atom attached to each carbon. • Each carbon atom uses three valence electrons to bond to hydrogen atom and two adjacent C atoms • Six electrons are shared equally among six carbon atoms

  26. Naming of Aromatic Hydrocarbon • When benzene has only one substituent the benzene ring is not numbered. • Example Chlorobenzene • When there are 2 or more substituents the benzene ring is numbered to give the lower numbers to the substituents. • Example 1,3-dichlorobenzene

  27. Common name of Aromatic Compounds

  28. Naming of Aromatic Hydrocarbon • When a common name such as toluene, phenol or aniline is used, the carbon atom attached to the methyl, hydroxyl, or amine group is number as carbon 1 • Example: 2-chlorotoluene • Example: 4-ethyltoluene

  29. Polycyclic Aromatic Compounds (PAHs)

  30. Polymer • Polymer are large molecules that consist of small units called monomers • Many are made by addition reaction of alkenes. Examples: • Polyethylene monomer is ethylene • Polyvinyl chloride monomer is vinyl chloride

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