Organic Chemistry 6 th Edition Paula Yurkanis Bruice

1. Chapter 20 More About Oxidation–Reduction Reactions Organic Chemistry 6th Edition Paula Yurkanis Bruice

2. Oxidation is always coupled with reduction. • Loss of electrons is oxidation. • Gain of electrons is reduction. • The oxidation state of a carbon atom equals the total • number of its C—O, C—N, and C—X bonds.

3. Reduction at carbon increases the number of C—H bonds or • decreases the number of C—O, C—N, or C—X bonds. • Oxidation at carbon decreases the number of C—H bonds or • increases the number of C—O, C—N, or C—X bonds.

4. Hydrogen, sodium borohydride, and hydrazine are the reducing agents:

5. Bromine and chromic acid are the oxidizing agents:

6. H2, Pd on charcoal Na or Li metal in liq NH3 NaBH4 or LiAlH4 H2 as a Reducing Agent

7. Reduction by Catalytic Hydrogenation Addition of two hydrogen atoms:

8. Only the alkene substituted to benzene is reduced: Reduction of carbon–nitrogen double and triple bonds:

9. Reduction of Ketones and Aldehydes

10. Rosenmund Reduction

12. Dissolving-Metal Reduction Addition of an electron, a proton, an electron, and a proton:

13. Reduction by Addition of a Hydride Ion and a Proton

14. Aldehydes, ketones, and acyl halides can be reduced to alcohols by sodium borohydrides:

15. LiAlH4 is a stronger reducing agent than NaBH4 LiAlH4 is used to reduce compounds that are unreactive toward NaBH4

16. DIBALH allows the addition of one equivalent of hydride to an ester: Replacing some of the hydrogens of LiAlH4 with –OR groups decreases the reactivity of the metal hydride:

17. Formation of Amines by Reduction

18. NaBH4 can be used to selectively reduce an aldehyde or a keto group in a compound: Alkenes and alkynes do not possess a partial positive charge:

19. Sodium borohydride can be used as a chemoselective reducing agent:

20. Oxidation of Alcohols

21. Oxidation of a Primary Alcohol

22. Mechanism of Alcohol Oxidation by the Swern Oxidation

23. Oxidation of Aldehydes and Ketones

24. The Tollens reagent oxidizes only aldehydes:

25. Both aldehydes and ketones can be oxidized by peroxyacid: the Baeyer–Villiger oxidation

27. Mechanism of the Baeyer–Villiger Oxidation

28. Predicting Baeyer–Villiger reaction products:

29. Controlling Stereochemistry in Synthesis An enantioselective reaction forms more of one enantiomer than of another:

31. Hydroxylation of Alkenes

32. Mechanism for cis-Glycol Formation Higher yields of the diol are obtained with osmium tetroxide than with permaganate

33. Oxidative Cleavage of 1,2-Diols

34. Summary of Alkene Hydroxylation Reactions

35. Permaganate Cleavage of Alkenes

36. Examples of permaganate-mediated alkene cleavage reactions:

37. Oxidative Cleavage of Alkenes by Ozonolysis Examples:

38. Structure of Ozone

39. The alkene and ozone undergo a concerted six-electron cycloaddition Mechanism of ozonide formation: The molozonide is unstable because it has two O—O bonds, but the ozonide is stable

40. Ozonides can be cleaved to carbonyl compounds:

41. Ozonolysis Mechanism 41

42. Examples of the Oxidative Cleavage of Alkenes by Ozonolysis

43. The benzene ring is not oxidized under mild ozonolysis conditions:

44. Oxidative Cleavage of Alkynes The same reagents that oxidize alkenes also oxidize alkynes:

45. Designing a Synthesis by Functional Group Interconversion Conversion of an aldehyde to other functional groups:

46. Conversion of a Ketone into an Ester or an Alcohol