REACTIONS OF ALDEHYDES AND KETONES

1. REACTIONS OF ALDEHYDES AND KETONES BY HARJEET GUJRAL ASSOCIATE PROFESSOR GOVT. COLLEGE ROPAR

2. Reactions of aldehydes and ketones: • oxidation • reduction • nucleophilic addition • Aldehydes are easily oxidized, ketones are not. • Aldehydes are more reactive in nucleophilic additions than ketones.

3. alkane alcohol reduction reduction aldehyde ketone addition product nucleophilic addition oxidation carboxylic acid

4. nucleophilic addition to carbonyl:

5. Mechanism:nucleophilic addition to carbonyl 1) 2)

6. Mechanism:nucleophilic addition to carbonyl,acid catalyzed 1) 2) 3)

7. Aldehydes & ketones, reactions: • Oxidation • Reduction • Addition of cyanide • Addition of derivatives of ammonia • Addition of alcohols • Cannizzaro reaction • Addition of Grignard reagents • 8) (Alpha-halogenation of ketones) • 9) (Addition of carbanions)

8. 1) Oxidation • Aldehydes(very easily oxidized!) • CH3CH2CH2CH=O + KMnO4, etc.  CH3CH2CH2COOH • carboxylic acid • CH3CH2CH2CH=O + Ag+ CH3CH2CH2COO- + Ag • Tollen’s test for easily oxidized compounds like aldehydes. • (AgNO3, NH4OH(aq)) Silver mirror

9. Ketones only oxidize under vigorous conditions via the enol.

10. b) Methyl ketones: Yellow ppt test for methyl ketones

11. 2) Reduction: • To alcohols

14. Then + H+ alcohol

15. Reduction b) To hydrocarbons

17. 3) Addition of cyanide

18. 1) 2)

19. Cyanohydrins have two functional groups plus one additional carbon. Nitriles can be hydrolyzed to carboxylic acids in acid or base:

20. 4) Addition of derivatives of ammonia

21. 1) 2) 3)

23. 5) Addition of alcohols

26. Cannizzaro reaction. (self oxidation/reduction) • a reaction ofaldehydes without α-hydrogens

27. Formaldehyde is the most easily oxidized aldehyde. When mixed with another aldehyde that doesn’t have any alpha-hydrogens and conc. NaOH, all of the formaldehyde is oxidized and all of the other aldehyde is reduced. Crossed Cannizzaro:

28. 7) Addition of Grignard reagents.

29. 1) 2)

30. #3 synthesis of alcohols. Used to build larger molecules from smaller organic compounds.

32. Planning a Grignard synthesis of an alcohol: • The alcohol carbon comes from the carbonyl compound. • The new carbon-carbon bond is to the alcohol carbon. New carbon-carbon bond

33. “The Grignard Song” (sung to the tune of “America the Beautiful”) Harry Wasserman The carbonyl is polarized, the carbon end is plus. A nucleophile will thus attack the carbon nucleus. The Grignard yields an alcohol of types there are but three. It makes a bond that corresponds from “C” to shining “C.”