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

2. 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. 3

4. 4 Label as alkane, alkene, or alkyne alkane alkene alkynealkene

5. 5 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)

6. 6 Name These propene 1-butene 2-butene 2-butyne

7. 7 Name These 2-methylpropene 3-bromo-3-chloro-1-butene 4,4-dibromo-1-butyne

8. 8 Draw These 1-chloro-1,2,2-trifluoroethene 1,2-dimethyl-1-cyclohexene 1,1,4,4-tetrabromo-2-pentyne

9. 9 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 o C trans-2-butene bp = 0.3 o C

10. 10

11. 11

12. 12

13. 13 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

14. 14 Write the names 1-pentene 4-chloro-1-pentene trans-3-heptene cis-1-bromo-1-butene

15. 15 Write the names cis-3,4-dibromo-3-hexene trans-3,4-dibromo-3-hexene trans-4,4,6,6-tetrabromo-2-hexene

16. 16 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 H 2 (hydrogenation) Addition of X 2 (halogenation) Addition of H 2 O (hydration)

17. 17 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

18. 18 Hydrogenation Double bonds react with 1 molecule of H 2 Triple bonds react with 2 molecules of H 2

19. 19 Write Product, Name Reactant & Product trans-4-methyl-2-pentene 2-methylpentane cyclopentene cyclopentane

20. 20 Halogenation Addition of bromine is useful for detection of carbon- carbon double bond Double bond reacts with 1 molecule of bromine

21. 21 Bromination Rapid decolorization of a bromine solution is characteristic of compound containing carbon-carbon double bond One cyclohexene molecule reacts with 1 molecule of bromine to give 1,2-dibromo cyclohexane

22. 22 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.

23. 23 Hydration

24. 24 Write Product, Name Reactant, 2-methyl-2-butene C 5 H 12 O cyclohexene C 6 H 12 O

25. 25 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

26. 26 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.

27. 27 3-D (Spatial) Drawings Draw a spatial drawing for butane Draw a spatial drawing for 2,2-dibromopropane

28. 28 3-D (Spatial) Drawings Do not show planar atoms with dashes or wedges Draw a spatial drawing for trans-1-bromo-1- propene

29. 29 Aromatic Hydrocarbon Benzene molecule, C 6 H 6, 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

30. 30 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

31. Common name of Aromatic Compounds 31

32. 32 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

33. Polycyclic Aromatic Compounds (PAHs) 33

34. 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 34

35. 35