1. Unsaturated Hydrocarbons

2. Introduction to Unsaturated HC – One or more C-to-C multiple bond present Double bond is rigid – doesn’t rotate – Similar physical properties to saturated HC – Very different chemical properties than sat’d HC Unsat’d HC are MUCH more reactive than saturated HC Reactions take place at the multiple bond

3. When a specific portion of the molecule determines its reactivity that part of the molecule is called a functional group – C-to-C multiple bonds are an example of a functional group

4. Classes of Unsaturated HC Alkenes – C-to-C double bond(s) present may be acyclic or cyclic Alkynes – C-to-C triple bond(s) present Aromatic – unsaturated cyclic HC that does not undergo addition reactions readily – Often a benzene ring present

5. Alkenes and Cycloalkenes Functional group: C=C – ALKENES: acyclic alkene General formula if only 1 double bond is present: C n H 2n ??same as……. Example: Cycloalkenes: cyclic alkene general formula if only one double bond is present: C n H 2n - 2 Example:

6. Naming Alkenes Name longest continuous chain that contains the double bond, suffix = “ene” – If C=C is same distance from both ends, start numbering from end closest to any substituent Locate C=C by giving # of the lowered numbered C in the double bond Use suffixes of “diene”, “triene”, tetrene” if more than one C=C – 1,3-hexadiene

7. Naming Cycloalkenes Name ring as you would a cycloalkane, but using suffix of “ene” – Cyclopentene….. no # needed to locate C=C If there are substituents on the ring – Cs of the double bond are C 1 and 2 – no #needed to locate C=C in name – Number so substituent(s) have lowest possible # – List in alphabetical order if more than 1 substituent

8. More naming Practice: Page 73, 16 and 20 Common Names to Know – Ethylene – Propylene

9. Line Angle Formulas Pretty straightforward Try a few on page 73: 26 & 28

10. Isomerism in Alkenes 1.Constitutional – Positional isomers…location of double different – Skeletal isomers …longest chain differs 2.Stereoisomers – Cis-trans isomers possible when: Each C in double bond has 2 different groups attached

11. Naturally Occurring Alkenes Pages 50-52 Good paper potential – Pheremones – Retenoids – Terpenes and isoprenes No coverage in lecture

12. Physical Properties 1.Nonpolar – Solubility 2.Density 3.MP and BP - trends 4.State at room temperature – For unbranched alkenes

13. Chemical Properties Alkenes 1.Combustion reaction 2.Addition reactions – Symmetrical: H 2 and X 2 – Unsymmetrical: HX and H-OH Markovnikov’s Rule applies 3.Polymerization reaction – Not covered, good paper topic

14. Alkynes Limited coverage in class See pages 62-64 ----------------------------------------

15. Bond Angles Alkanes Alkenes Alkynes

16. Aromatic Hydrocarbons Cyclic unsaturated HC that does not undergo addition reactions – delocalized electrons electrons present Our focus will be on benzene based aromatic HC – Structure – Naming conventions – Properties: physical and chemical (selected)

17. Benzene and Benzene Derivatives Benzene Toluene – NOT methylbenzene Single substituent – put name of substituent in front of benzene – Chlorobenzene – tertbutylbenzene

18. 2 Substituents - 2 Naming Options 1.Number system – Locate substituents with #s – Goal is lowest possible set of #s – When substituents differ, that with alphabetical priority is assigned #1…see top of page 68 – When a methyl group is one of the substituents…. 2.Ortho, meta, para system – 2 methyl groups  a xylene

19. Benzene as a Substituent! Benzene “hanging off” a chain = a phenyl group – See example 2.6 c on page 68

20. Properties of Aromatic HC (benzene) 1.Physical properties – You know these….polarity, solubility, density, state of matter of benzene 2.Chemical properties – many, text covers 2 – Alkylation: + R-Cl AlCl 3 catalyst required – Halogenation: + X 2 FeX 3 catalyst required