1 CHE 102 Chap 19 Chapter 20 Unsaturated Hydrocarbons

2 CHE 102 Chap 19 Unsaturated Hydrocarbons Alkenes (C=C) Alkynes ( ) Aromatic C

3 CHE 102 Chap 19 sp 2 Hybridization (C=C)

4 CHE 102 Chap 19

5 sp – Hybridization ( ) C

6 CHE 102 Chap 19 IUPAC Rules for Naming Alkenes Select the longest continuous carbon-carbon chain that contains the double bond. Name this parent compound as you would an alkane but change the –ane ending to -ene; for example, propane is changed to propene. propane propene

7 CHE 102 Chap 19 IUPAC Rules Continued Number the carbon chain of the parent compound starting with the end nearer to the double bond. Use the smaller of the two numbers to indicate the position of the double bond. Place this number in front of the alkene name; for example, 2-butene means that the carbon-carbon double bond is between carbons 2 and 3.

8 CHE 102 Chap 19 IUPAC Rules Continued Branch chains and other groups are treated as in naming alkanes, by numbering and assigning them to the carbon atom to which they are bonded.

9 CHE 102 Chap 19 Two or more C=C double bonds 1,3-butadiene Four carbon atoms Inserted To ease pronunciation Two Double bonds Position of the double bonds

10 CHE 102 Chap 19 Cycloalkenes Just like normal cycloalkanes except the numbering always starts at the double bond. cyclohexene chlorocyclohexene

11 CHE 102 Chap 19 Geometric Isomers (Cis/Trans) Structural Isomers –Same formula –Different structure Geometric Isomers –Same formula –Same structure –Different geometry

12 CHE 102 Chap 19 No geometric isomers for C-C “free rotation”

13 CHE 102 Chap 19 Different Properties = Different Molecules (bp=60.1°C) (bp= 48.4°C)

14 CHE 102 Chap 19 Cis vs Trans

15 CHE 102 Chap 19 Two groups the same cis and trans cannot be used if 2 of the same groups are on one side of the double bond. –These do not have isomerism

16 CHE 102 Chap 19 Isomers of C 5 H 10

17 CHE 102 Chap 19 CC Chain H H CC H H Cis/Trans Isomers in Biology

18 CHE 102 Chap 19 Reactions of Alkenes Alcohols –Dehydration/Hydration Oxidation Addition –Hydrogenation –Halogenation x2 –Hydration –Markovnikov’s Rule

19 CHE 102 Chap 19 Alkenes and Alcohols Dehydration Hydration

20 CHE 102 Chap 19 Oxidation PurpleBrown “Bayer Test for C=C”

21 CHE 102 Chap 19 Hydrogenation (Addition)

22 CHE 102 Chap 19 Halogenation (Addition) Reddish-Orange Clear

23 CHE 102 Chap 19 Addition Reactions

24 CHE 102 Chap 19 Dilemma

25 CHE 102 Chap 19 Carbocations

26 CHE 102 Chap 19 Markovnikov’s Rule When an unsymmetrical molecule such as HX(HCl) adds to a carbon-carbon double bond, the hydrogen from HX goes to the carbon atom that has the greater number of hydrogen atoms.

27 CHE 102 Chap 19

28 CHE 102 Chap 19 Alkynes IUPAC Rules for Naming ane  yne Use # to indicate position of triple bond Reactions: –Combustion –Halogenation –Addition Properties –Low Bp/Mp (Lower Mass) –Non-polar –Very reactive

29 CHE 102 Chap 19 Aromatic Structure

30 CHE 102 Chap 19 Naming Sidechains:

31 CHE 102 Chap 19 Special Aromatics

32 CHE 102 Chap 19 Disubstituted ortho meta para

33 CHE 102 Chap 19 Examples

34 CHE 102 Chap 19 Special Cases o-xylene p-xylene m-xylene

35 CHE 102 Chap 19 Poly Substituted # ring to give lowest overall numbers Special groups always labeled #1

36 CHE 102 Chap 19 Reactions Halogenation Nitration Alkyl substitution Side chain oxidation

37 CHE 102 Chap 19 Halogenation

38 CHE 102 Chap 19 Nitration Nitric acid nitrobenzene

39 CHE 102 Chap 19 Alkyl Substitution benzenechloroethane ethylbenzene

40 CHE 102 Chap 19 Side Chain Oxidation

41 CHE 102 Chap 19 Alkynes C