Aldehydes and Ketones And Carboxylic Acids

1. Aldehydes and Ketones And Carboxylic Acids Mrs. Shinde U.M.

2. Aldehydes and Ketones

3. ALDEHYDES AND KETONES “carbonyl” functional group: Aldehydes Ketones

4. Nomenclature: Aldehydes, common names: Derived from the common names of carboxylic acids; drop –ic acid suffix and add –aldehyde. CH3 CH3CH2CH2CH=O CH3CHCH=O butyraldehyde isobutyraldehyde (α-methylpropionaldehyde)

6. Aldehydes, IUPAC nomenclature: Parent chain = longest continuous carbon chain containing the carbonyl group; alkane, drop –e, add –al. (note: no locant, -CH=O is carbon #1.) CH3 CH3CH2CH2CH=O CH3CHCH=O butanal 2-methylpropanal H2C=O CH3CH=O methanal ethanal

7. Ketones, common names: Special name:acetone “alkyl alkyl ketone” or “dialkyl ketone”

8. (o)phenones: Derived from common name of carboxylic acid, drop –ic acid, add –(o)phenone.

9. Ketones: IUPAC nomenclature: Parent = longest continuous carbon chain containing the carbonyl group. Alkane, drop –e, add –one. Prefix a locant for the position of the carbonyl using the principle of lower number.

10. Oxidation/Reduction: oxidation numbers: oxidation -4 -2 0 +2 +4 CH4 CH3OH H2C=O HCO2H CO2 alkane alcohol aldehyde carboxylic acid reduction

11. Aldehydes synthesis 1) oxidation of primary alcohols: RCH2-OH + K2Cr2O7, special conditions  RCH=O RCH2-OH + C5H5NHCrO3Cl  RCH=O (pyridinium chlorochromate) [With other oxidizing agents, primary alcohols  RCOOH]

13. Aldehyde synthesis: 2) Ozonolysis of alkenes

14. Aldehyde synthesis: 4) Calcium salts of Acids HCHO + CaCO3 3

15. Aldehyde synthesis: 5) alkyl nitriles and esters

16. Aldehyde synthesis: 6) aromatic hydrocarbons

17. Aldehyde synthesis: 7) acyl chloride

18. Ketone synthesis: 1) oxidation of secondary alcohols

20. Ketone synthesis: 2) Friedel-Crafts acylation Aromatic ketones (phenones) only!

21. Carboxylic acids: R-COOH, R-CO2H, Common names: HCO2H formic acid L. formica ant CH3CO2H acetic acid L. acetum vinegar CH3CH2CO2H propionic acid G. “first salt” CH3CH2CH2CO2H butyric acid L. butyrum butter CH3CH2CH2CH2CO2H valeric acid L. valerans

22. 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.

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

24. nucleophilic addition to carbonyl:

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

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

27. 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)

28. 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

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

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

31. 2) Reduction: • To alcohols

34. Reduction b) To hydrocarbons

36. 3) Addition of cyanide

37. 4) Addition of derivatives of ammonia

39. 5) Addition of alcohols

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

42. 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:

43. 7) Addition of Grignard reagents.

44. #3 synthesis of alcohols. Used to build larger molecules from smaller organic compounds.

46. 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

47. Carbonyl Condensation Reactions The Aldol Reaction • In the aldol reaction, two molecules of an aldehyde or ketone react with each other in the presence of a base to form a -hydroxy carbonyl compound.

48. Carbonyl Condensation Reactions The Aldol Reaction • The mechanism of the aldol reaction occurs in three steps.

49. Carbonyl Condensation Reactions The Aldol Reaction • The aldol reaction is a reversible equilibrium, so the position of the equilibrium depends on the base and the carbonyl compound. • ¯OH Is the base typically used in an aldol reaction. Although with ¯OH only a small amount of enolate is formed, this is appropriate because the starting aldehyde is needed to react with the enolate in the second step of the reaction. • Aldol reactions can be carried out with either aldehydes or ketones. With aldehydes, the equilibrium usually favors products, but with ketones the equilibrium favors the starting materials. However, there are ways of driving the equilibrium to the right.

50. Carbonyl Condensation Reactions The Aldol Reaction • Recall that the characteristic reaction of aldehydes and ketones is nucleophilic addition. An aldol reaction is a nucleophilic addition in which an enolate is the nucleophile. Figure 24.1 The aldol reaction—An example of nucleophilic addition