Organic chemistry for medicine and biology students Organic B Chapter 18 Aldehydes and Ketones

1. Organic chemistry for medicine and biology students Organic B Chapter 18 Aldehydes and Ketones By Prof. Dr. Adel M. Awadallah Islamic University of Gaza

5. Nomenclature of Aldehydes and Ketones Common aldehydes

6. Common Ketones

7. Nomenclature of aldehydes and ketones (al) aldehyde, (one) ketone alkanes < alkenes < OH < ketone < aldehyde < acid < ester Examples

10. Acyl groups

11. Common aldehydes and ketones

14. Synthesis of aldehydes and Ketones • Oxidation of Alcohols primary gives aldehydes using PCC secondary gives ketones 2) Friedel-Crafts 3) From Alkynes

15. 4- Aldehydes from Acid Chlorides

16. 5- Ketones from Acid Chlorides

18. Synthesis of Alkylbenzenes

20. Reduction of Acids and their derivatives by Lithium Aluminum hydride (LAH)

27. Naturally occuring aldehydes and Ketones

28. The carbonyl group

29. Reactions of the carbonyl group

31. Remember: Generation of a chiral center

33. A. Hydration and Hemiacetal Formation • Water adds rapidly to the carbonyl function of aldehydes and ketones. In most cases the resulting hydrate (a geminal-diol) is unstable relative to the reactants and cannot be isolated. • Exceptions to this rule exist, • one being formaldehyde (a gas in its pure monomeric state). • Thus, a solution of formaldehyde in water (formalin) is almost exclusively the hydrate, or polymers of the hydrate. • Another is chloral hydrate

34. Addition of Alcohols

35. Examples

38. Addition of hydrogen cyanide to aldehydes and ketones

39. Reducing Agents The reduction of an aldehyde You get exactly the same organic product whether you use lithium tetrahydridoaluminate or sodium tetrahydridoborate. For example, with ethanal you get ethanol:

40. The reduction of a ketone • Again the product is the same whichever of the two reducing agents you use. • For example, with propanone you get propan-2-ol: • Reduction of a ketone leads to a secondary alcohol.

42. REACTION OF ALDEHYDES AND KETONES WITH GRIGNARD REAGENTS

43. The reaction between Grignard reagents and methanal The reaction between Grignard reagents and other aldehydes The reaction between Grignard reagents and ketones

45. Reaction with Acetylides

46. OXIDATION OF ALDEHYDES AND KETONES

48. Cannizzaro reaction. (self oxidation/reduction) • a reaction ofaldehydes without α-hydrogens The Cannizzaro reaction, named after its discoverer Stanislao Cannizzaro, is a chemical reaction that involves the base-induced disproportionation of an aldehyde.[1][2] Cannizzaro first accomplished this transformation in 1853, when he obtained benzyl alcohol and potassium benzoate from the treatment of benzaldehyde with potash (potassium carbonate). More typically, the reaction would be conducted with sodium or potassium hydroxide:

49. Mechanism of the Cannizzaro Reaction

50. Crossed Cannizzaro: 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.