1. Carey Chapter 4 – Alcohols and Alkyl Halides Figure 4.2 YSU

2. 4.1 Functional groups – a look aheadYSU

3. 4.2 IUPAC nomenclature of alkyl halides Functional class nomenclature pentyl chloridecyclohexyl bromide1-methylethyl iodide Substitutive nomenclature 2-bromopentane3-iodopropane2-chloro-5-methylheptaneYSU

4. 4.3 IUPAC nomenclature of alcohols 1-pentanol cyclohexanol 2-propanol 2-pentanol 1-methyl cyclohexanol 5-methyl-2-heptanolYSU

5. 4.4 Classes of alcohols and alkyl halides Primary (1 o ) Secondary (2 o ) Tertiary (3 o )YSU

6. 4.5 Bonding in alcohols and alkyl halidesYSU Figure 4.1

7. 4.5 Bonding in alcohols and alkyl halides Figure 4.2YSU

8. 4.6 Physical properties – intermolecular forces CH 3 CH 2 CH 3 CH 3 CH 2 FCH 3 CH 2 OH propane fluoroethane ethanol b.p. -42 o C -32 o C 78 o CYSU

9. Figure 4.4 4.6 Physical properties – intermolecular forcesYSU

10. 4.6 Physical properties – water solubility Alkyl halides are generally insoluble in water (useful) alcohols Figure 4.5YSU

11. 4.7 Preparation of alkyl halides from alcohols and HXYSU

12. 4.8 Mechanism of alkyl halide formation

13. 4.8 Energetic description of mechanism - Step 1 : protonation Figure 4.6 YSU

14. 4.8 Energetic description of mechanism - Step 2 : carbocation formation Figure 4.7 YSU

15. 4.8 Energetic description of mechanism - Step 3 : trapping carbocation Figure 4.9 YSU

16. 4.9 Full mechanism “pushing” curved arrowsYSU

17. 4.9 Full S N 1 mechanism showing energy changes Figure 4.11 YSU

18. 4.10 Carbocation structure and stability Figure 4.8 Figure 4.15 HyperconjugationYSU

19. 4.10 Relative carbocation stability Figure 4.12YSU

20. 4.11 Relative rates of reaction of R 3 COH with HX Relative Rates of Reaction for Different Alcohols with HX Related to the stability of the intermediate carbocation:YSU

21. 4.11 Relative rates of reaction of R 3 COH with HX Rate-determining step involves formation of carbocation Figure 4.16YSU

22. 4.12 Reaction of methyl and 1 o alcohols with HX – S N 2

23. 4.12 Substitution Reaction Mechanism - S N 2 Transition state Alternative pathway for alcohols that cannot form a good carbocation Rate determining step is bimolecular (therefore S N 2) Reaction profile is a smooth, continuous curve (concerted) YSU

24. Convenient way to halogenate a 1 o or 2 o alcohol Avoids use of strong acids such as HCl or HBr Usually via S N 2 mechanism 4.13 Other methods for converting ROH to RXYSU

25. 4.14 Free Radical Halogenation of Alkanes R-H + X 2 R-X + H-X Types of bond cleavage: heterolytic homolyticYSU

26. 4.15 Free Radical Chlorination of MethaneYSU

27. 4.16 Structure and stability of Free Radicals Orbital hybridization models of bonding in methyl radical (Figure 4.17) YSU

28. 4.16 Bond Dissociation Energies (BDE)

29. 4.17 Mechanism of Methane Chlorination

30. 4.17 Mechanism for Free Radical Chlorination of MethaneYSU

31. 4.18 Free Radical Halogenation of Higher AlkanesYSU

32. YSU Radical abstraction of H is selective since the stability of the ensuing radical is reflected in the transition state achieved during abstraction. Lower energy radical, formed faster

33. 4.18 Free Radical Halogenation of Higher Alkanes Figure 4.16 YSU

34. 4.18 Bromine radical is more selective than chlorine radical Consider propagation steps – endothermic with Br·, exothermic with Cl· YSU

35. 4.18 Bromine radical is more selective than chlorine radical Consider propagation steps – endothermic with Br·, exothermic with Cl· YSU Bromination – late TS looks a lot like radical Chlorination – early TS looks less like radical