1. Chapter 12 Amines
Suggested Problems: 24-6,30-32,34-5,36,38,50,54

2. Amines – Organic Nitrogen Compounds
Organic derivatives of ammonia, NH3
Nitrogen atom with a lone pair of electrons, making amines both basic and nucleophilic
Occur in plants and animals

3. 12.1 Naming Amines
Alkyl-substituted (alkylamines) or aryl-substituted (arylamines)
Classified: 1⁰ (RNH2), 2⁰ (R2NH), 3⁰ (R3N)

4. Quaternary Ammonium Ions
A nitrogen atom with four attached groups is positively charged
Compounds are quaternary ammonium salts

5. IUPAC Names – Simple Amines
For simple amines, the suffix -amine is added to the name of the alkyl substituent

6. IUPAC Names – “-amine” Suffix
The suffix -amine is added to the name of the organic substituent
The prefixes “di”, “tri”, etc. can be used as dictated by the structure

7. IUPAC Names – Amines with More Than One Functional Group
Consider the –NH2 as an amino substituent on the parent molecule

8. IUPAC Names – Multiple Alkyl Groups
Symmetrical secondary and tertiary amines are named by adding the prefix di- or tri- to the alkyl group

9. IUPAC Names – Multiple, Different Alkyl Groups
Named as N-substituted primary amines
Largest alkyl group is the parent name, and other alkyl groups are considered N-substituents

10. Common Names of Heterocyclic Amines
If the nitrogen atom occurs as part of a ring, the compound is designated as being heterocyclic
Each ring system has its own parent name

11. 12.2 Properties of Amines Bonding to N is similar to that in ammonia
N is sp3-hybridized
C–N–C bond angles are close to 109⁰ tetrahedral value

12. Amines Form H-Bonds
Amines with fewer than five carbons are water-soluble
Primary and secondary amines form hydrogen bonds, increasing their boiling points

13. 12.3 Basicity of Amines
The lone pair of electrons on nitrogen makes amines basic and nucleophilic
They react with acids to form acid–base salts and they react with electrophiles

14. Relative Basicity
Amines are stronger bases than alcohols, ethers, or water
Amines establish an equilibrium with water in which the amine becomes protonated and hydroxide is produced
The most convenient way to measure the basicity of an amine (RNH2) is to look at the acidity of the corresponding ammonium ion (RNH3+)
High pKa → weaker acid and stronger conjugate base.

15. General Patterns of Basicity
Table 12.1: pKa values of ammonium ions
Most simple alkylammmonium ions have pKa's of 10 to 11
Arylamines and heterocyclic aromatic amines are considerably less basic than alkylamines (conjugate acid pKa 5 or less)

16. Basicity of Some Common Amines

17. Basicity of Arylamines
The N lone-pair electrons in arylamines are delocalized by interaction with the aromatic ring  electron system and are less able to accept H+ than are alkylamines

18. Substituted Arylamines
Can be more basic or less basic than aniline
Electron-donating substituents (such as –CH3, –NH2, –OCH3) increase the basicity of the corresponding arylamine
Electron-withdrawing substituents (such as –Cl, –NO2, –CN) decrease arylamine basicity

19. Amides
Amides (RCONH2) in general are not proton acceptors except in very strong acid
The C=O group is strongly electron-withdrawing, making the N a very weak base

20. Purification of Amines
Purification can be achieved owing to the basicity of amines

21. 12.4 Synthesis of Amines
Reduction of amides (Section 10.10) and nitriles (Section 10.11)

22. SN2 Reactions of Alkyl Halides
Ammonia and other amines are good nucleophiles

23. Reductive Amination of Aldehydes and Ketones
Treatment of an aldehyde or ketone with ammonia or an amine in the presence of a reducing agent

24. Mechanism of Reductive Amination

25. Reductive Amination Is Versatile
Ammonia, primary amines, and secondary amines yield primary, secondary, and tertiary amines, respectively

26. Reduction of Nitrobenzenes
Arylamines are prepared from nitration of an aromatic compound and reduction of the nitro group
Reduction by catalytic hydrogenation over platinum is suitable if no other groups can be reduced
Iron, zinc, tin, and tin(II) chloride are effective in acidic solution

27. 12.5 Reactions of Amines
Alkylation and acylation have already been presented

28. Reaction with Aldehydes and Ketones
Converts amines into imines (Section 9.9)
Occurs in biological pathways

29. 12.6 Heterocyclic Amines
A heterocycle is a cyclic compound that contains atoms of two or more elements in its ring, usually C along with N, O, or S

30. Pyrole Pyrole is an amine and a conjugated diene,
however its chemical properties are not consistent with either of these structural features

31. Common Five-Membered Aromatic Heterocycles

32. Pyridine
Pyridine is the nitrogen-containing heterocyclic analog of benzene
Lone pair is not part of the p orbital system
Basic properties

33. Substituted Pyridines
Important biologically such as the B6 complex vitamins

34. Fused-Ring Aromatic Heterocycles

35. 12.7 Alkaloids: Naturally Occurring Amines
Naturally occurring amines derived from plant sources
Most have pronounced biological properties
Many are pharmaceutical agents
Few of the total in existence have been characterized
Currently active area of research