1. Chapter 9 Ketones and Aldehydes

2. Carbonyl Compounds

3. Carbonyl Structure Carbon is sp2 hybridized.
C=O bond is shorter, stronger, and more polar than C=C bond in alkenes.

4. IUPAC Names for Ketones
Replace -e with -one. Indicate the position of the carbonyl with a number.
Number the chain so that carbonyl carbon has the lowest number.
For cyclic ketones the carbonyl carbon is assigned the number 1.
Chapter 9

5. Examples 3-methyl-2-butanone 3-methylbutan-2-one 3-bromocyclohexanone
4-hydroxy-3-methyl-2-butanone
4-hydroxy-3-methylbutan-2-one
Chapter 9

6. Naming Aldehydes IUPAC: Replace -e with -al.
The aldehyde carbon is number 1.
If -CHO is attached to a ring, use the suffix -carbaldehyde.
Chapter 9

7. Examples 3-methylpentanal 2-cyclopentenecarbaldehyde
cyclopent-2-en-1-carbaldehyde
Chapter 9

8. Name as Substituent
On a molecule with a higher priority functional group, C=O is oxo- and -CHO is formyl.
Aldehyde priority is higher than ketone.
3-methyl-4-oxopentanal
3-formylbenzoic acid
Chapter 9

9. Common Names for Ketones
Named as alkyl attachments to -C=O.
Use Greek letters instead of numbers.
methyl isopropyl ketone
a-bromoethyl isopropyl ketone
Chapter 9

10. Historical Common Names
acetone
acetophenone
benzophenone
Chapter 9

11. -bromobutyraldehyde
Aldehyde Common Names
Use the common name of the acid.
Drop -ic acid and add -aldehyde.
1 C: formic acid, formaldehyde
2 C’s: acetic acid, acetaldehyde
3 C’s: propionic acid, propionaldehyde
4 C’s: butyric acid, butyraldehyde.
5 C’s: valeric acid, valeraldehyde
-bromobutyraldehyde
3-bromobutanal γ β α
Chapter 9

12. Boiling Points
More polar, so higher boiling point than comparable alkane or ether.
Cannot H-bond to each other, so lower boiling point than comparable alcohol.
Chapter 9

13. Solubility Good solvent for alcohols.
Lone pair of electrons on oxygen of carbonyl can accept a hydrogen bond from O-H or N-H.
Acetone and acetaldehyde are miscible in water.
Chapter 9

14. Formaldehyde Gas at room temperature.
Formalin is a 40% aqueous solution.
trioxane, m.p. 62C
formaldehyde,
b.p. -21C
formalin
Chapter 9

15. Industrial Importance
Acetone and methyl ethyl ketone are important solvents.
Formaldehyde used in polymers like Bakelite.
Flavorings and additives like vanilla, cinnamon, artificial butter.
Chapter 9

16. Synthesis Review Oxidation Ozonolysis of alkenes.
2 alcohol + Na2Cr2O7  ketone
1 alcohol + PCC  aldehyde
Ozonolysis of alkenes.
Chapter 9

17. Synthesis Review (2) Friedel-Crafts acylation
Acid chloride/AlCl3 + benzene  ketone
Hydration of terminal alkyne
Use HgSO4, H2SO4, H2O for methyl ketone
Chapter 9

18. Aldehydes from Acid Chlorides
Use a mild reducing agent to prevent reduction to primary alcohol.
Chapter 9

19. Ketones from Acid Chlorides
Use lithium dialkylcuprate (R2CuLi), formed by the reaction of 2 moles of R-Li with cuprous iodide.
Chapter 9

20. Nucleophilic Addition
A strong nucleophile attacks the carbonyl carbon, forming an alkoxide ion that is then protonated.
A weak nucleophile will attack a carbonyl if it has been protonated, thus increasing its reactivity.
Aldehydes are more reactive than ketones.
Chapter 18

21. Addition of Water In acid, water is the nucleophile.
In base, hydroxide is the nucleophile.
Aldehydes are more electrophilic since they have fewer e--donating alkyl groups.
a gemdiol
a gemdiol
Chapter 9

22. Addition of Alcohol
Chapter 9

23. Mechanism Must be acid-catalyzed.
Adding H+ to carbonyl makes it more reactive with weak nucleophile, ROH.
Hemiacetal forms first, then acid-catalyzed loss of water, then addition of second molecule of ROH forms acetal.
All steps are reversible.
Chapter 9

24. Mechanism for Hemiacetal
Oxygen is protonated.
Alcohol is the nucleophile.
H+ is removed =>
Chapter 9

25. Hemiacetal to Acetal
Chapter 9

26. Oxidation of Aldehydes
Easily oxidized to carboxylic acids.
Chapter 18

27. Cyclic Acetals Addition of a diol produces a cyclic acetal.
Sugars commonly exist as acetals or hemiacetals.
Chapter 9

28. Tollens Test
Add ammonia solution to AgNO3 solution until precipitate dissolves.
Aldehyde reaction forms a silver mirror.
=>
Chapter 18

29. SILVER MIRROR

30. Reduction Reagents
Sodium borohydride, NaBH4, reduces C=O, but not C=C.
Lithium aluminum hydride, LiAlH4, much stronger, difficult to handle.
Hydrogen gas with catalyst also reduces the C=C bond.
Chapter 18

31. Catalytic Hydrogenation
Widely used in industry.
Raney nickel, finely divided Ni powder saturated with hydrogen gas.
Pt and Rh also used as catalysts.
Chapter 18

32. Tautormers
Constitutional isomers in equilibrium with each other that differ in the location of a hydrogen atom and a double bond are called tautomers.
A case of tautomerization occurs with ketones (aldehydes) that are in equilibrium with their enol form, which are called keto enol tautomers

33. ALDEHYDE AND KETONE REVIEW

34. Name a. Cis-2-pentenal b. Cis-2-pentanal c. Trans-2-pentenal
d. Trans-2-pentanal

35. Answer a. Cis-2-pentenal b. Cis-2-pentanal c. Trans-2-pentenal
d. Trans-2-pentanal
The aldehyde is in position one. The double bond is trans.

36. Name a. 2-Oxobutanoic acid b. 2-Butanone-1-carbaldehyde
c. 2-Oxopentanoic acid
d. 3-Oxopentanoic acid

37. Answer a. 2-Oxobutanoic acid b. 2-Butanone-1-carbaldehyde
c. 2-Oxopentanoic acid
d. 3-Oxopentanoic acid
The carbon in the carboxylic acid is position one.

38. Identify the chemical name for acetone.
a. Methanal
b. Ethanal
c. Propanone
d. Butanone

39. Answer a. Methanal b. Ethanal c. Propanone d. Butanone
Acetone is called propanone or dimethyl ketone.

40. a. 2-Propanone
b. 2-Butanone
c. 2-Pentanone
d. 3-Pentanone

41. Answer a. 2-Propanone b. 2-Butanone c. 2-Pentanone d. 3-Pentanone
2-Butanone is formed in the Grignard reaction. The secondary alcohol is oxidized to a ketone with sodium dichromate.

42. a. 2-Propanone
b. 2-Butanone
c. 2-Pentanone
d. 3-Pentanone

43. Answer a. 2-Propanone b. 2-Butanone c. 2-Pentanone d. 3-Pentanone
The ethyl group adds to the carbonyl carbon.

44. a. 2,2-Diethoxypropane
b. 2-Ethoxy-2-propanol
c. Propane-2,2-diol
d. 2-Ethoxypropane

45. Answer a. 2,2-Diethoxypropane b. 2-Ethoxy-2-propanol
c. Propane-2,2-diol
d. 2-Ethoxypropane
Two molecules of ethanol are added to the carbonyl, with loss of water.

46. a. 1-Propanol
b. Propanoic acid
c. Propane-1,1-diol
d. 1-Hydroxypropanoic acid

47. Answer a. 1-Propanol b. Propanoic acid c. Propane-1,1-diol
d. 1-Hydroxypropanoic acid
The Tollens reagent reduces an aldehyde to a carboxylic acid.

48. a. 2-Butanone
b. 2-Butanol
c. 2-Hexanone
d. Butane

49. Answer a. 2-Butanone b. 2-Butanol c. 2-Hexanone d. Butane
Butanone is reduced to 2-butanol.

50. End of Chapter 9
Chapter 9