Organic Chemistry Aldehydes and Ketones

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Organic ChemistryAldehydes and Ketones

• Chapter 17

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Aldehydes and Ketones

• Carbonyl Group CO
• Present in aldehydes and ketones

Aldehydes
Ketones
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Aldehydes

• Aldehydes
• Sometimes abbreviated RCHO
• Contain at least one H connected to the C

Aldehydes
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Ketones

• Ketones
• Carbonyl C is connected to two alkyl groups
• RCOR

Ketones
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Nomenclature

• IUPAC
• Suffix is -al for the aldehydes
• Suffix is -one for the ketones
• indicates position of ketone

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Nomenclature
NOTE Ketone, Not keytone
From Yahoo Images
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Nomenclature

• An Aldehyde or Ketone takes precedence over any
  previously considered group

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Nomenclature

• Common names - aldehydes

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Nomenclature

• Common names - ketones
• Some are always used

- Others name each R group and end with ketone
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Physical Properties

• Carbonyls
• Cannot form H bonding with each other
• There is NOT an H connected to a F, N, O
• Aldehydes and Ketones are POLAR molecules and
  form dipole interactions
• Gives higher boiling and melting points

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Physical Properties

• Aldehydes and Ketones
• can form H bonds with water!
• solubility in water is about the same as alcohols

yes!
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Physical Properties

• Strong odors
• Ketones generally have pleasant odors
• perfumes, flavoring agents
• Aldehydes odors vary
• some pleasant
• cinnaminaldehyde, vanillin
• some not pleasant
• formaldehyde
• Many are found in natural products

http//www.youtube.com/watch?vKDohVakqkic
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How do you make Aldehydes?

• Aldehydes from Oxidation of 1o alcohols
• Problem is over oxidation to ACID!

Practice a couple ..
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How do you make Ketones?

• Ketones from Oxidation of 2o alcohols

Practice a couple ..
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Oxidation of Aldehydes

• Aldehydes are easily oxidized
• KMnO4
• K2Cr2O7
• even air oxidation carboxylic acid!

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Oxidation of Ketones

• Ketones resist oxidation
• under mild or normal conditions, no reaction
• more severe conditions yield mixtures
• CO2 and H2O under extreme conditions

This difference in reactivity can be used to
Tell the difference between an aldehyde and
ketone
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Reaction

• 1. Oxidation Tollens Test
• - Benedicts Test
• 2. Reduction Hydrogen addition
• NaBH4 reagent
• 3. Addition of Alcohols hemiacetal/acetal
• and tautomerism

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Tollens Test

• The Silver Mirror Test
• Oxidation of Aldehydes
• Ag ion in aq. ammonia
• NO reaction with KETONES
• Ag(NH3)2 aldehyde

Silver Mirror
Ag 2 NH3 Ag(NH3)2
Ag(NH3)2 RCHO Ago RCOO- 4NH3
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Benedicts Test

• Oxidation of Aldehydes
• Cu ion, aqueous
• Orange to red ppt.
• NO reaction with KETONES

Cu aldehyde Cu(oxide)
acid
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Benedicts Test

• Oxidation of Aldehydes
• overall reaction

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Chemical Properties

• Addition to CO
• Other reactions are ADDITION Reactions
• Bond is polar ? and ?-
• Negatives are attracted to C
• Positives are attracted to O

-

B
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Addition of H2

• Reduction to Alcohols
• Hydrogen gas and a catalyst (Ni, Pd, Pt)
• Similar to alkene to alkane reduction

B
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Addition of H2

• Reduction to Alcohols
• Will reduce ketones to 2o alcohols
• Slower reaction than reduction of CC
• CC is reduced faster (first) if both CO and CC

B
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Addition of H2 using NaBH4

• Reduction to Alcohols
• NaBH4 does not allow the reaction of the carbon
  carbon double bond

B
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Addition of Alcohol

• In the addition of R-OH to form an acetal the
  First step is the formation of a hemiacetal
• This is when an -OH and -OR are both on same C

B
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Formation of Acetals

• IF strong acid (HCl) is present, a second alcohol
  reacts to form the acetal (two -OR groups on C)

H2O
B
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Addition of Alcohol - Acetals
Step 1
Step 2
H2O
B
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Formation of Acetals

• Addition of R-OH
• acid catalyzed, 2 moles of alcohol react

?
B
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Formation of Acetals

• Addition of R-OH
• acid catalyzed, 2 moles of alcohol react

Draw the Hemi
B
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Formation of Acetals

• Acetal reaction in equilibrium

B
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Formation of Acetals

• Acetal reactions

?
B
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Formation of Acetals

• Acetal reactions

?
1o alcohol
B
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Formation of Acetals

• Hemiacetal reactions (formation of hemiacetals)
• likely when within the same molecule

1o alcohol
B
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Formation of Acetals

• Cyclic hemiacetals
• Reacts with a 2nd. molecule of alcohol
• Results in a cyclic acetal

1o alcohol
B
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Formation of Acetals

• Which are hemiacetals / acetals?

1
2
3
4
5
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7
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9
10
B
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Keto-Enol Tautomerism

• Equilibrium that exists
• Keto (carbonyl) to Enol (alkene/alcohol)

B
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Keto-Enol Tautomerism

• Equilibrium called Tautomerism

1o alcohol
B
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Keto-Enol Tautomerism

• Equilibrium called Tautomerism

Most enols are less stable
1o alcohol
B
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Important Compounds

• Formaldehyde
• Gas at RT
• Soluble in H2O
• Formalin
• 37 formaldehyde
• found in labs
• preserves by denaturing proteins
• Used to produce polymers

B
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Important Compounds

• Acetaldehyde
• bp 21o C
• Converted to trimer
• 3 units of acetaldehyde
• called paraldehyde
• once used as a hypnotic/sleep-producer

B
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Important Compounds

• Acetone
• bp 56o C
• Infinitely soluble in H2O
• Excellent industrial solvent
• paints, varnishes, resins
• coatings, nail polish
• Produced in the body
• diabetic ketoacidosis
• acetone breath

B
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Important Compounds

• ?-chloroacetophenone
• lachrymators
• tearing of eyes, etc.
• Used as a tear gas
• Active ingredient in Mace

B