Chap 14: ALDEHYDES AND KETONES

1

• Chap 14 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.

2

• 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

• 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

4

• PHYSICAL PROPERTIES
• The carbonyl group is moderately polar, but it
  doesnt have any hydrogen atoms attached, so it
  cannot hydrogen bond between molecules.

5

• PHYSICAL PROPERTIES, cont.
• 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.

6

• PHYSICAL PROPERTIES, cont.
• The CO group can hydrogen bond with water
  molecules.
• This makes low molecular weight aldehydes and
  ketones water soluble (they have small
  hydrophobic sections).

H H
O R-C-R
O
7

• ALDEHYDE AND KETONE REACTIONS
• Recall the oxidation of alcohols to produce
  aldehydes and ketones

8

• REACTIONS, cont.
• The addition of H2 in the presence of catalysts.

9

• Examples

10

• REACTIONS, cont.
• The addition of alcohols to aldehydes produces an
  unstable hemiacetal intermediate.

11

• REACTIONS, cont.
• General formulas for
• Hemiacetals
• Acetals

12

• REACTIONS, cont.
• The addition of alcohol to ketones produces an
  unstable hemiketal intermediate.

13

• REACTIONS, cont.
• General formula for
• Hemiketal
• Ketal

14

• REACTIONS, cont.
• Cyclical hemiacetals and hemiketals are more
  stable than open chains and are important in
  carbohydrate chemistry.

15

• REACTIONS, cont.
• Acetals and ketals are stable, but may be
  converted back to aldehydes and ketones through
  acid catalyzed hydrolysis. Hydrolysis is the
  breakage of a bond by reaction with water.
• Acetal hydrolysis

16

• REACTIONS, cont.
• Ketal hydrolysis
• Specific Example

17

• 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

18

• IMPORTANT ALDEHYDES AND KETONES, cont.
• Acetone
• (propanone)
• Important organic solvent
• Used in such things as nail polish remover
• Miscible with water

19

• IMPORTANT ALDEHYDES AND KETONES, cont.
• Progesterone and testosterone (female and male
  sex hormones) are ketones.
• Some aldehydes and ketones are very fragrant and
  are used in flavorings.
• Vanillin (vanilla)
• Cinnamaldehyde (cinnamon)
• Citral (citrus flavoring)
• Camphor (medicinal odor)