2. Aldehydes and Ketones. II. Oxidation and Reduction; Synthesis Chapter 17

3. Assignment for Chapter 17 Skip the following sections: Section 17.3 Sections 17.13 through 17.15

4. Problem Assignment In-Text Problems –17-1, 2, 3, 4 –5 (NH 2 -NH 2 is misssing from the problem!!) –6 - 1115, 17, 18 End-of-Chapter Problems –1, 2, 3

5. Oxidation and reduction -- an overview Oxidation: add O or remove H 2 Reduction: remove O or add H 2 Oxidation numbers are relatively useless for carbon!

6. Sect. 17.1: Hydride as a nucleophile

7. Reactions of sodium borohydride Aldehydes yield primary alcohols Ketones yield secondary alcohols Esters give no reaction! Amides give no reaction!

8. Keep water away from lithium aluminum hydride! LiAlH 4 + 4 H 2 O LiOH + Al(OH) 3 + 4 H 2

9. Reactions of lithium aluminum hydride Aldehydes give primary alcohols Ketones give secondary alcohols Esters give primary alcohols from the carboxylic acid part of the ester Amides give primary amines!!

10. Sect. 17.2: Reduction of carbonyl groups with hydrogen You really have to “pound” on carbonyl compounds to reduce them by using hydrogen under high pressure! Aldehydes give primary alcohols Ketones give secondary alcohols Other carbonyl compounds, such as esters are virtually unreactive.

11. Selective reduction of C=C and C=O bonds Hydrogen/ Pt (low pressure): reduces C=C but not the C=O group Sodium borohydride: reduces C=O but not the C=C group

12. Sect. 17.4: The Clemmensen Reduction

13. Sect. 17.5: Wolff-Kishner Reduction

14. Sect. 17.6: Raney Nickel Desulfurization

15. Sect. 17.7: Oxidations NOTE: A dehydrogenation is also a form of oxidation!

16. Oxidation: an overview Mild oxidizers:CrO 3 in pyridine CrO 3 in acetone CrO 3 in acetone pyridinium chlorochromate (PCC) Primary alcohols give aldehydes Secondary alcohols give ketones Strong oxidizers: K 2 Cr 2 O 7 in acid CrO 3 in acid KMnO 4 Primary alcohols give carboxylic acids Secondary alcohols give ketones

17. Oxidation of Primary Alcohols with KMnO 4

18. Sect. 17.8: Oxidation of Primary Alcohols with K 2 Cr 2 O 7 (Jones) Jones Oxidation

19. Oxidation of Secondary Alcohols Jones Oxidation

20. Sect. 17.9: Oxidation with Chromic Oxide and Pyridine Sarett Oxidation

21. Important!! Sarrett reaction: Primary alcohols get oxidized to aldehydes Aldehydes are not further oxidized to carboxylic acids

22. Sect. 17.10: Oxidation with Pyridinium Chlorochromate “PCC” Oxidation

23. Important!! PCC reactions: Primary alcohols get oxidized to aldehydes Aldehydes are not further oxidized to carboxylic acids

24. Sect. 17.11: Silver and Copper oxidation of aldehydes Tollens: oxidation with silver ion yields a carboxylic acid; Ag + is reduced to Ag o (silver mirror) Benedict’s: oxidation with copper ion yields a carboxylic acid; Cu 2+ is reduced to Cu + (Cu 2 O)

25. Sect. 17.12: Reducing and non- reducing sugars Carbohydrates that have hemi acetal structures are in equilibrium with a “free” aldehyde ---- reducing sugars Carbohydrates that are in the acetal form, do not have free aldehyde --- non-reducing Reducing sugar =positive Tollens/Benedicts Non-reducing sugar = negative tests

26. Sect. 17.16: Biological reduction and oxidation

27. Nicotinamide Adenine Dinucleotide (NADH)

28. Reduction of Acetaldehyde in Fermentation

29. Reduction of Pyruvic Acid in Muscle Tissue

30. Sect. 17.17: Preparation of aldehydes by reduction

31. Sect. 17.18: Ketone Synthesis using Organometallic Reagents Acid chlorides give ketones with lithium dialkyl cuprates Acid chlorides give ketones with Grignard reagents, but only at low temperatures

32. Ketone Synthesis using Lithium Dialkylcuprates

33. Sect. 17.19: Synthesis Problem

34. Now, how do we do this?

35. Are We Having Fun Yet?

36. Let’s Make Some Drugs! Protecting group is required!

37. Another Synthesis Problem