ALDEHYDES AND KETONES

1. ALDEHYDES AND KETONES

2. Aldehydes and Ketones

3. d+ d- Most Reactive Group – p-electrons + polarisation al – aldehydes, one - ketones Names Propanal Methanal (formaldehyde) Ethanal (acetaldehyde) Pentanal

4. Nomenclature of Aldehydes

5. If the aldehyde group is attached to a ring,

6. Nomenclature of Ketones

8. Oxidation

9. An aldehyde has a greater partial positive charge on itscarbonyl carbon than does a ketone

10. Steric factors contribute to the reactivity of an aldehyde • The carbonyl carbon of an aldehyde is more accessible • to the nucleophile • Ketones have greater steric crowding in their transition • states, so they have less stable transition states

11. Reactions 1. Redox reactions

12. Aldehyde hydrate (ketone: ) 2. Addition: AN Addition of water Addition of bisulfite Bisulfite

13. Aldehyde ammonia (ketone: ) Addition of NH3 Addition of HCN Cyanohydrine

14. Ammonia derivatives 3. Condensation reactions (addition followed by elimination) Primary amine Schiff base

15. Hydroxylamine Oxime Hydrazine Hydrazone

16. Phenylhydrazine Phenylhydrazone 2,4-dinitrophenylhydrazine 2,4-dinitrophenylhydrazone

17. Aldol condensation Aldol

18. Reaction with alcohol Hemiacetal (addition!) Acetal (condensation!)

19. Keto–Enol Tautomerism

20. Oxidation of a Primary Alcohol

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

23. Aldehydes and ketones react with nucleophiles to form addition products: nucleophile addition reactions

25. Water adds to an aldehyde or ketone to form a hydrate

26. R O C •• •• R' HOH R •• •• HO O H C •• •• R' Hydration of Aldehydes and Ketones

27. R O C •• •• R' R"OH R •• •• R"O O H C •• •• R' Alcohols Under Analogous Reactionwith Aldehydes and Ketones • Product is called a hemiacetal.

28. O CH CH(OCH2CH3)2 Example + 2CH3CH2OH HCl + H2O Benzaldehyde diethyl acetal (66%)

29. Reaction with Primary Amines:Imines

30. If the nucleophile that adds to the aldehyde or ketone is an O or an N, a nucleophilic addition–elimination reaction will occur

31. •• •• + H H2N HN C O C O •• •• •• •• R R a carbinolamine •• N + H2O C (imine) R Imine (Schiff's Base) Formation

32. O CH Example + CH3NH2 CH=NCH3 + H2O N-Benzylidenemethylamine (70%)

33. + NG + R2C H2O H2N G O R2C NOH R2C H2N OH hydroxylamine oxime Reaction with Derivatives of Ammonia

34. + NG + R2C H2O H2N G O R2C NOH R2C H2N OH hydroxylamine oxime NNH2 R2C H2N NH2 hydrazine hydrazone etc. Reaction with Derivatives of Ammonia

35. O C NNH2 C Example + H2NNH2 + H2O (73%)

36. O + H2NNH NNH CCH3 + H2O a phenylhydrazone (87-91%) Example CCH3 phenylhydrazine

37. An aldol addition product loses water to form an aldol condensation product

38. O O RCH2CH CHCH 2RCH2CH R OH Aldol Condensation NaOH

39. O O NaOH, H2O 2CH3CH CH3CH CH2CH 5°C OH Aldol Addition of Acetaldehyde Acetaldol(50%)

40. R •• •• R"O OR C •• •• R' R •• •• R"O O H C •• •• R' Hemiacetal reacts further in acid to yield an acetal • Product is called an acetal. ROH, H+ Product is called a hemiacetal.

41. O HCH Formaldehyde • formaldehyde cannot form an enolate • formaldehyde is extremely reactive toward nucleophilic addition

42. O H2C CHCH Acrolein

43. O H2C CHCH Acrolein

44. O H2C CHCH Acrolein