organic chemistry aldehydes and ketones l.
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Organic Chemistry Aldehydes and Ketones. Chapter 17. Aldehydes and Ketones. Carbonyl Group C=O Present in aldehydes and ketones. Aldehydes. Ketones. Aldehydes. Aldehydes Sometimes abbreviated RCHO Contain at least one H connected to the C. Aldehydes. Ketones. Ketones

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aldehydes and ketones
Aldehydes and Ketones
  • Carbonyl Group C=O
    • Present in aldehydes and ketones

Aldehydes

Ketones

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

Aldehydes

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

Ketones

nomenclature
Nomenclature
  • IUPAC
    • Suffix is “-al” for the aldehydes
    • Suffix is “-one” for the ketones
    • # indicates position of ketone
nomenclature6
Nomenclature

NOTE:

Ketone,

Not keytone

From Yahoo Images

nomenclature7
Nomenclature
  • An Aldehyde or Ketone takes precedence over any previously considered group
nomenclature8
Nomenclature
  • Common names - aldehydes
nomenclature9
Nomenclature
  • Common names - ketones
    • Some are always used

- Others name each R group and end with “ketone”

physical properties
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
physical properties11
Physical Properties
  • Aldehydes and Ketones
    • can form H bonds with water!
    • solubility in water is about the same as alcohols

yes!

physical properties12
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?v=KDohVakqkic

how do you make aldehydes
How do you make Aldehydes?
  • Aldehydes from Oxidation of 1o alcohols
    • Problem is over oxidation to ACID!

Practice a couple …………..

how do you make ketones
How do you make Ketones?
  • Ketones from Oxidation of 2o alcohols

Practice a couple …………..

oxidation of aldehydes
Oxidation of Aldehydes
  • Aldehydes are easily oxidized
    • KMnO4
    • K2Cr2O7
    • even air oxidation carboxylic acid!
oxidation of ketones

[O]

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

reaction
Reaction

1. Oxidation – Tollens Test

- Benedicts Test

2. Reduction – Hydrogen addition

– NaBH4 reagent

3. Addition of Alcohols – hemiacetal/acetal

and tautomerism

tollen s test
Tollen’s 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

benedict s test

Cu+

Cu2+

Benedict’s Test
  • Oxidation of Aldehydes
    • Cu++ ion, aqueous
    • Orange to red ppt.
    • NO reaction with KETONES

Cu+++ aldehyde Cu+(oxide)+ acid

benedict s test21

Cu2O

Benedict’s Test
  • Oxidation of Aldehydes
    • overall reaction
chemical properties
Chemical Properties
  • Addition to C=O
    • Other reactions are ADDITION Reactions
    • Bond is polar + and -
    • Negatives are attracted to C
    • Positives are attracted to O

-

+

B

addition of h 2
Addition of H2
  • Reduction to Alcohols
    • Hydrogen gas and a catalyst (Ni, Pd, Pt)
    • Similar to alkene to alkane reduction

B

addition of h 224
Addition of H2
  • Reduction to Alcohols
    • Will reduce ketones to 2o alcohols
    • Slower reaction than reduction of C=C
      • C=C is reduced faster (first) if both C=O and C=C

B

addition of h 2 using nabh 4
Addition of H2 using NaBH4
  • Reduction to Alcohols
    • NaBH4 does not allow the reaction of the carbon carbon double bond

B

addition of alcohol
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

formation of acetals
Formation of Acetals

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

+ H2O

B

formation of acetals29
Formation of Acetals
  • Addition of R-OH
    • acid catalyzed, 2 moles of alcohol react

?

B

formation of acetals30
Formation of Acetals
  • Addition of R-OH
    • acid catalyzed, 2 moles of alcohol react

Draw the Hemi

B

formation of acetals31
Formation of Acetals
  • Acetal reaction in equilibrium

B

formation of acetals32
Formation of Acetals
  • Acetal reactions

?

B

formation of acetals33
Formation of Acetals
  • Acetal reactions

?

1o alcohol

B

formation of acetals34

H

O

O

OH

5

4

3

2

1

O

5

1

CH

CH

CH

CH

CH

or

2

2

2

2

2

4

OH

O

3

a cyclic hemiacetal

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

1o alcohol

B

formation of acetals35
Formation of Acetals
  • Cyclic hemiacetals
    • Reacts with a 2nd. molecule of alcohol
    • Results in a cyclic acetal

1o alcohol

B

formation of acetals36
Formation of Acetals
  • Which are hemiacetals / acetals?

1

2

3

4

5

6

7

8

9

10

B

keto enol tautomerism
Keto-Enol Tautomerism
  • Equilibrium that exists
  • Keto (carbonyl) to Enol (alkene/alcohol)

B

keto enol tautomerism38

Keto form

(more stable)

(less stable)

Keto-Enol Tautomerism
  • Equilibrium called Tautomerism

1o alcohol

B

keto enol tautomerism39
Keto-Enol Tautomerism
  • Equilibrium called Tautomerism

Most enols are

less stable

1o alcohol

B

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

B

important compounds41
Important Compounds
  • Acetaldehyde
    • bp 21o C
    • Converted to trimer
      • 3 units of acetaldehyde
      • called paraldehyde
      • once used as a hypnotic/sleep-producer

B

important compounds42
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

important compounds43
Important Compounds
  • -chloroacetophenone
    • lachrymators
      • tearing of eyes, etc.
    • Used as a tear gas
    • Active ingredient in “Mace”

B