© 2011 Pearson Education, Inc.

Chapter 12

Carbonyl Compounds IIReactions of Aldehydes and Ketones

More Reactions of Carboxylic Acid Derivatives

ORGANIC CHEMISTRY, 2ND EDITION

PAULA YURKANIS BRUICE

RAED M. AL-ZOUBI, ASSISTANT PROFESSOR OF CHEMISTRY

DEPARTMENT OF CHEMISTRY - N4L0

JORDAN UNIVERSITY OF SCIENCE AND TECHNOLOGY

© 2011 Pearson Education, Inc.

Chapter 18 2

Nomenclature of Aldehydes

• IUPAC: Replace -ewith -al.

• The aldehyde carbon is number 1.

• If -CHO is attached to a ring, use the suffix -carbaldehyde.

=>

© 2011 Pearson Education, Inc.

3

Exmaples

© 2011 Pearson Education, Inc.

4

If the aldehyde group is attached to a ring,

© 2011 Pearson Education, Inc.

5

If a compound has two functional groups, the one with thelower priority is indicated by its prefix:

© 2011 Pearson Education, Inc.

Chapter 18 6

Nomenclature of Ketones

• Replace -ewith -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.

=>

© 2011 Pearson Education, Inc.

7

Examples

The carbonyl is assumed to be at the 1-position in cyclicketones:

© 2011 Pearson Education, Inc.

8

If a ketone has a second functional group of higherpriority…

A few ketones have common names:

© 2011 Pearson Education, Inc.

Chapter 18 9

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.

CH3 C CH

CH3

CH2 C H

OO

COOH

CHO

3-methyl-4-oxopentanal 3-formylbenzoic acid=>

© 2011 Pearson Education, Inc.

Relative Reactivity of Aldehydes and Ketones

Nucleophilic Addition reactions

© 2011 Pearson Education, Inc.

11

An aldehyde has a greater partial positive charge on itscarbonyl carbon than does a ketone:

The partial positive charge on the carbonyl carbon causesthat carbon to be attacked by nucleophiles:

© 2011 Pearson Education, Inc.

12

• The carbonyl carbon of an aldehyde is more accessibleto the nucleophile.

• Ketones have greater steric crowding in their transition states, so they have less stable transition states.

• Steric factors contribute to the reactivity of an aldehyde.

Aldehydes are More Reactive Than Ketones

© 2011 Pearson Education, Inc.

13

The reactivity of carbonyl compounds is also related tothe basicity of Y–:

© 2011 Pearson Education, Inc.

14

Carboxylic acid derivatives undergo nucleophilic acylsubstitution reactions with nucleophiles:

© 2011 Pearson Education, Inc.

15

Aldehydes and ketones undergo nucleophilic additionreactions with nucleophiles:

This is an irreversible nucleophilic addition reaction if the nucleophile is a strong base

© 2011 Pearson Education, Inc.

16

A reversible nucleophilic addition reaction:

© 2011 Pearson Education, Inc.

17

Grignard ReagentsThe Formation of a New Carbon–

Carbon Bond

Grignard reagents react with aldehydes, ketones, andcarboxylic acid derivatives

© 2011 Pearson Education, Inc.

18

Grignard reagents are used to prepare alcohols:

© 2011 Pearson Education, Inc.

19

Mechanism for the reaction of an ester with a Grignardreagent:

© 2011 Pearson Education, Inc.

20

Examples of Grignard Reactions

© 2011 Pearson Education, Inc.

21

Reactions of Carbonyl Compounds with Hydride Ion

Reduction of Carbonyl compounds

© 2011 Pearson Education, Inc.

22

© 2011 Pearson Education, Inc.

23

Mechanism for the reaction of an acyl chloride withhydride ion:Reagents: NaBH4, LiAlH4, NaH, DIBALH

© 2011 Pearson Education, Inc.

24

Mechanism for the reaction of an ester with hydride ion:

Esters and acyl chlorides undergo two successive reactions with hydride ion and Grignard reagents

© 2011 Pearson Education, Inc.

25

Utilization of DIBALH to Control the Reduction Reaction

© 2011 Pearson Education, Inc.

26

The reduction of a carboxylic acid with LiAlH4 forms a single primary alcohol:

Acyl chloride is also reduced by LiAlH4 to yield an alcohol

© 2011 Pearson Education, Inc.

27

An amide is reduced by LiAlH4 to an amine

Mechanism for the reaction of an N-substituted amide with hydride ion:

© 2011 Pearson Education, Inc.

28

Selectivity of Reductions

© 2011 Pearson Education, Inc.

Addition of Amines to aldehydes and Ketones

Imine and Enamine Formations

© 2011 Pearson Education, Inc.

30

Aldehydes and ketones react with a primary amine toform an imine:

This is a pH-dependent nucleophilic addition–elimination reaction

© 2011 Pearson Education, Inc.

An enamine undergoes an acid-catalyzed hydrolysis toform a carbonyl compound and a secondary amine 31

Aldehydes and ketones react with secondary amines toform enamines:

© 2011 Pearson Education, Inc.

Addition of Water and alcohol to aldehydes and Ketones

Geminal diol, hemiaceal and acetal Formations

© 2011 Pearson Education, Inc.

33

Water adds to an aldehyde or ketone to form a hydrate:

© 2011 Pearson Education, Inc.

34

Mechanism for acid-catalyzed hydrate formation:

© 2011 Pearson Education, Inc.

35

Addition of an Alcohol to an Aldehyde or a Ketone

© 2011 Pearson Education, Inc.

36

Mechanism for acid-catalyzed acetal or ketal formation:

© 2011 Pearson Education, Inc.

37

Utilization of Protecting Groups in Synthesis

LiAlH4 will reduce the ester to yield an alcohol, butthe keto group will also be reduced

© 2011 Pearson Education, Inc.

38

The keto group is protected as a ketal in this synthesis:

The more reactive aldehyde is protected with the diolbefore reaction with the Grignard reagent:

© 2011 Pearson Education, Inc.

39

Stereochemistry

© 2011 Pearson Education, Inc.

40