ALDEHYDES AND KETONES

1
(No Transcript)
2
ALDEHYDES AND KETONES

• The carbonyl group
• Aldehydes have at least one hydrogen attached to
  the carbonyl group.

• Ketones have two carbons attached to the
  carbonyl group.

3
NAMING ALDEHYDES

• Find the longest carbon chain that contains the
  aldehyde group.
• Change ending of the root hydrocarbon name by
  dropping e and adding al.
• All other branches and groups are named and
  located using standard IUPAC system.
• Examples

3-bromobutanal
2-ethylbutanal
4
COMMON ALDEHYDES
5
NAMING KETONES

• Find the longest chain that contains CO.
• Using the root alkane name, drop the e ending
  and change to one.
• Number the longest carbon chain so the CO group
  has the lowest number.
• Name and number other substituents as before.
• Examples

3-methyl-2-pentanone
2-methylcyclohexanone
6
COMMON KETONES
7
PHYSICAL PROPERTIES

• The carbonyl group is moderately polar, but it
  doesnt have any hydrogen atoms bonded to the
  oxygen atom, so it cannot hydrogen bond between
  molecules.

8
PHYSICAL PROPERTIES (continued)

• Because of the polarity of the CO group, these
  groups can interact, but the attraction is not as
  strong as hydrogen bonding.
• This makes the boiling point of aldehydes and
  ketones higher than alkanes, but lower than
  alcohols.

9
PHYSICAL PROPERTIES (continued)
10
PHYSICAL PROPERTIES (continued)

• The CO group can hydrogen bond with water
  molecules because the oxygen atom in the carbonyl
  group has a partial negative charge that attracts
  the partial positive charge of a hydrogen atom in
  the water molecule.
• This makes low molecular weight aldehydes and
  ketones water soluble (they have small
  hydrophobic sections).

11
PHYSICAL PROPERTIES (continued)
12
ALDEHYDE AND KETONE REACTIONS

• Recall the oxidation of alcohols to produce
  aldehydes and ketones

13
ALDEHYDE AND KETONE REACTIONS (continued)

• The difference in reactivity toward oxidation is
  the chief reason why aldehydes and ketones are
  classified in separated families.

14
ALDEHYDE AND KETONE REACTIONS (continued)

• The ease with which aldehydes are oxidized allows
  us to test for the presence of aldehydes with
  Tollens reagent or Benedicts reagent.
• In general, ketones fail to react with these
  reagents.

From left to right, three test tubes containing
potassium dichromate (K2Cr2O7), acetone, and
benzaldehyde.
After the addition of equal amounts of K2Cr2O7,
the acetone remains unreacted, whereas the
benzaldehyde is oxidized.
15
ALDEHYDE AND KETONE REACTIONS (continued)

• In the presence of aldehydes, Tollens reagent
  produces a silver coating on glass.
• This method is used to produce mirrors and silver
  ornaments.

16
ALDEHYDE AND KETONE REACTIONS (continued)

• In the presence of aldehydes, Benedicts reagent
  produces a red precipitate.

The addition of Benedicts reagent from the first
tube produces colors (due to the red Cu2O) that
indicate the amount of glucose present.
From left to right, three test tubes containing
Benedicts reagent, 0.5 glucose solution, and
2.0 glucose solution.
17
ALDEHYDE AND KETONE REACTIONS (continued)

• The addition of H2 in the presence of catalysts.

18
ALDEHYDE AND KETONE REACTIONS (continued)

• Examples

19
ALDEHYDE AND KETONE REACTION MAP
20
IMPORTANT ALDEHYDES AND KETONES

• Formaldehyde
• Gas at room temperature
• Formalin 37 aqueous solution
• Sterilizer
• Embalming fluid
• Starting material for plastics such as Formica
  and Bakelite

21
IMPORTANT ALDEHYDES AND KETONES (continued)

• Acetone
• Important organic solvent
• Used in such things as nail polish remover
• Miscible with water

22
IMPORTANT ALDEHYDES AND KETONES (continued)

• Progesterone and testosterone (female and male
  sex hormones) are ketones.

23
IMPORTANT ALDEHYDES AND KETONES (continued)

• Some aldehydes and ketones are very fragrant and
  are used in flavorings.
• Vanillin (vanilla)
• Cinnamaldehyde (cinnamon)
• Citral (citrus flavoring)
• Camphor (medicinal odor)

24
IMPORTANT ALDEHYDES AND KETONES (continued)
25
IMPORTANT ALDEHYDES AND KETONES (continued)