Chapter 23 Amines Organic Chemistry - PowerPoint Presentation

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Chapter 23 Amines Organic Chemistry - PPT Presentation

Second Edition David Klein Copyright 2015 John Wiley amp Sons Inc All rights reserved Klein Organic Chemistry 2e 231 Introduction to Amines Amines are derivatives of ammonia Amines are designated as primary secondary or tertiary ID: 714965

klein organic amp wiley organic klein wiley amp chemistry reserved rights sons 2015 john copyright amines preparation reactions practice

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Slide1

Chapter 23Amines

Organic ChemistrySecond Edition

David Klein

Klein, Organic Chemistry 2e Slide2

23.1 Introduction to AminesAmines are derivatives of ammonia

Amines are designated as primary, secondary, or tertiaryThe terms, 1°, 2°,and 3° are used differently for amines than for alcohols. HOW?

23-2Slide3

23.1 Introduction to AminesThere are hundreds of examples of amines found in natural products

3Slide4

23.1 Introduction to AminesSome naturally occurring amines take part in neurochemistry

23.1 Introduction to AminesThe trigonal pyramidal nitrogen atom of an amine carries a partial negative charge on its lone pair

HOW do you think the amine is likely to react?

Klein, Organic Chemistry 2e

23-5Slide6

23.1 Introduction to AminesAmines often react as a base or as a nucleophile

What feature(s) of the amine do you think might determine whether it is more likely to act as a base or as a nucleophile?

Klein, Organic Chemistry 2e 23-6Slide7

23.3 Properties of AminesThe N atom in typical amines is

sp3 hybridized

The angles are 108 degrees. WHY?

The C-N bond lengths are 147 pm, which is slightly shorter than C-C bonds. WHY?Under what circumstances would the nitrogen be

sp2 hybridized?

Klein, Organic Chemistry 2e

23-

7Slide8

23.3 Properties of AminesN atoms with three different alkyl groups are chiral

Chiral compounds are generally optically active. WHAT does that mean?Amine are generally not optically active. WHY? See next slide

8Slide9

23.3 Properties of Amines

23.3 Properties of AminesMany small molar mass amines have unpleasant odors

Practice with conceptual checkpoint 23.4 and 23.5

Klein, Organic Chemistry 2e

23-10Slide11

Let’s review all of the methods we’ve learned in previous chapters to synthesize amines

Carbon skeleton expanded by 1 carbon23.4 Preparation of Amines: A Review

Klein, Organic Chemistry 2e 23-11Slide12

Let’s review all of the methods we’ve learned in previous chapters to synthesize amines

Carbon skeleton is not changed23.4 Preparation of Amines: A Review

Klein, Organic Chemistry 2e

23-12Slide13

Let’s review all of the methods we’ve learned in previous chapters to synthesize amines

Reduction with a metal is a bit more mild than reduction with H2. WHY might mild conditions be preferred?23.4 Preparation of Amines: A Review

23-

13Slide14

Let’s review all of the methods we’ve learned in previous chapters to synthesize amines

Why is NaOH used in a final step?Practice with conceptual checkpoints 23.10 and 23.11

23-

14Slide15

Let’s learn some new amine syntheses

Explain WHY the reaction will not stop at the primary amine but will continue to form a quaternary ammonium salt23.5 Preparation of Amines via Substitution Reactions

23-16Slide17

Let’s learn some new amine syntheses

See mechanism on next few slides

23.5 Preparation of Amines via Substitution Reactions

23-17Slide18

23-18Slide19

23.5 Preparation of Amines via Substitution ReactionsN2 is a great leaving group. WHY?

23-19Slide20

23.5 Preparation of Amines via Substitution ReactionsThe Gabriel synthesis produces primary amines as well

First, potassium phthalimide is formed

Although the N

1- is stabilized by resonance, it is still nucleophilic

Klein, Organic Chemistry 2e

23-

20Slide21

23.5 Preparation of Amines via Substitution Reactions

Klein, Organic Chemistry 2e 23-21Slide22

23.5 Preparation of Amines via Substitution ReactionsThe last step generally employs aqueous acid or hydrazine

Practice with

SkillBuilder

Klein, Organic Chemistry 2e

23-

22Slide23

23.6 Preparation of Amines via Reductive AminationRecall the method for forming imines

If a reducing agent is present, the imine can be reduced in situ to form an amine

Reductive amination can be accomplished with a variety of reducing agents

Klein, Organic Chemistry 2e 23-

24Slide25

Sodium cyanoborohydride, which is similar to NaBH4, is commonly used

The inductive effects of the –CN group make the cyanoborohydride reagent more selectiveHOW?

23.6 Preparation of Amines via Reductive Amination

23-25Slide26

23.6 Preparation of Amines via Reductive AminationWhy can’t NaBH4 be used for reductive aminations?

Practice with SkillBuilder

Klein, Organic Chemistry 2e 23-26Slide27

23.7 Synthetic StrategiesLet’s review reactions that form amines

30Slide31

23.7 Synthetic StrategiesLet’s review reactions that form amines

Practice with SkillBuilder

23-31Slide32

23.8 Acylation of AminesRecall that amines can attack acyl chlorides

Two moles of the amine are used. WHY?Polysubstitution is not observed. WHY?An acyl group can act as a protecting group. HOW?An

acyl group can help to limit the reactivity of amines in EAS reactions – see next slide

Klein, Organic Chemistry 2e 23-35Slide36

23.8 Acylation of AminesHow might you perform the following synthesis?

Adding bromine won’t work, because polysubstitution can not be avoided

Klein, Organic Chemistry 2e

23-

36Slide37

23.8 Acylation of AminesHow might you perform the following synthesis?

The disadvantage of this synthesis is that amide hydrolysis requires harsh conditions

Klein, Organic Chemistry 2e

23-37Slide38

23.8 Acylation of AminesAromatic amines also can not undergo Friedel Crafts directly

How does the addition of the AlCl3 group deactivate the ring?

Klein, Organic Chemistry 2e 23-

38Slide39

23.8 Acylation of AminesTo achieve ring alkylation, first the amine must be

acylated

Practice with conceptual checkpoints 23.22 through 23.24

Klein, Organic Chemistry 2e

23-39Slide40

23.9 The Hofmann EliminationLike alcohols, amines can be converted into leaving groups for elimination reactions

Klein, Organic Chemistry 2e 23-41Slide42

23.9 The Hofmann EliminationLike alcohols, amines can be converted into leaving groups for elimination reactions

Unexpectedly, the less substituted (less stable) product is observed – see next slide

23-42Slide43

23.9 The Hofmann EliminationSterics in the

anticoplanar conformation hinders attack at the more substituted site. Draw an energy diagram

23-43Slide44

23.11 Reactions of Aryldiazonium IonsAlkyl diazonium salts are extremely reactive (potentially explosive) because of the excellent N2

23-47Slide48

23.11 Reactions of Aryldiazonium Ions

Klein, Organic Chemistry 2e 23-48Slide49

23.11 Reactions of Aryldiazonium IonsExplain each step in the synthesis below

A fluorine can also be installed

Klein, Organic Chemistry 2e

23-49Slide50

23.11 Reactions of Aryldiazonium IonsThere are many other diazonium salt substitutions

Using this synthesis, amines can be used as a directing group and subsequently replaced with a –H atomPractice with conceptual checkpoint 23.30

Klein, Organic Chemistry 2e

23-51Slide52

23.11 Reactions of Aryldiazonium IonsDiazonium salts can also be attacked by aromatic rings with an activating group – EAS mechanism

Klein, Organic Chemistry 2e

23-55Slide56

23.11 Reactions of Aryldiazonium IonsAzo

coupling produces azo dyesWHY are azo compounds colored?

Varying the substitution on the rings affects the specific dye color

Practice with SkillBuilder

23.6

Klein, Organic Chemistry 2e

23-

56Slide57

Additional Practice ProblemsGive an appropriate name for the following molecule

Klein, Organic Chemistry 2e

23-

62Slide63

Additional Practice ProblemsPredict the major product for the following reaction

Klein, Organic Chemistry 2e

23-

63Slide64

Additional Practice ProblemsGive necessary reagents to make the secondary amine below

Klein, Organic Chemistry 2e

23-

64Slide65

Additional Practice ProblemsGive necessary reagents for the synthesis below

Klein, Organic Chemistry 2e

23-

Chapter 23 Amines Organic Chemistry - PowerPoint Presentation

Chapter 23 Amines Organic Chemistry - PPT Presentation

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