1. Chapter 23 The Chemistry of Amines

2. Amines

3. skatole

4. Classification of Amines
Amines are organic derivatives of ammonia
Note how amines are classified differently from that of alcohols
23.1 Nomenclature of Amines

5. Common Nomenclature
For simple amines, add “amine” to the name of the alkyl group
When alkyl groups differ, name the amine as an N-substituted amine

6. Aromatic amines are named as derivatives of aniline
Common Nomenclature
Aromatic amines are named as derivatives of aniline
23.1 Nomenclature of Amines

7. Substitutive Nomenclature
Amines are named in a similar fashion to the their analogous alcohols
Remove the “-e” and replace it with “-amine”
If there is more than one amino group, use Greek prefixes to indicate how many and numbers to indicate location on the alkyl chain
23.1 Nomenclature of Amines

8. When alkyl groups differ, use the N-substitution system
When there is more than one substituted amine, use N and N’ to differentiate

9. Name the amino group as a substituent when there is a higher priority principal group
Recall:

10. Substitutive Nomenclature
Heterocyclic amines

11. Problems
Name the following compounds:

12. Draw the following molecules
2-propen-1-amine
N-methyl-N’-propyl-1,4-butanediamine
p-aminophenol

13. Most amines undergo rapid inversion at N
Structure of Amines
Bond length:
Most amines undergo rapid inversion at N
23.2 Structure of Amines

14. Physical Properties of Amines
H-bonding ability increases boiling point
Low molecular weight amines tend to be water soluble whether they are primary, secondary or tertiary
Fewer than 5 carbons usually = solubility in water
Diethylamine, MW = 71.1 amu
bp = 56.3°C
Pentane, MW = 72.1 amu
bp = 36.1°C

16. Basicity of Amines
Amines react with acids to form ammonium salts

17. Separations Using Amine Basicity
Ammonium salts are ionic compounds which imparts a high degree of water-solubility
This property can be useful in separation of amines from other compounds

18. Acidity of Amines
NH3, RNH2, and R2NH are amphoteric: they may act as bases and acids
They are very weakly acidic
Will give up H+ to a very strong base
The conjugate base of an amine is called an amide (do not confuse with amide derivatives of carboxylic acids)

19. Quaternary Salts
Quaternary ammonium and phosphonium salts are compounds in which all four groups around the N and P are alkyl or aryl
23.6 Quaternary Ammonium and Phosphonium Salts

20. Phase-Transfer Catalysis

21. Synthesis of Amines

22. Direct Alkylation of Amines
Further alkylations can take place to give complex mixtures

23. Gabriel Synthesis of Primary Amines
Direct alkylation is not a good method for the preparation of primary amines
The Gabriel synthesis allows for controlled preparation
23.11 Synthesis of Amines

24. Hydrolysis of the phthalimide frees the amine
23.11 Synthesis of Amines

25. Reduction of Nitro Compounds
Catalytic hydrogenation:
Reduction with finely divided metal powders:
23.11 Synthesis of Amines

26. Reduction of Nitro Compounds
LiAlH4 and NaBH4 fail to provide the amine
23.11 Synthesis of Amines

27. Reductive Amination

29. Formaldehyde can be used to introduce methyl groups

30. Neither an imine nor an enamine can be an intermediate in the reaction of a secondary amine and formaldehyde
23.7 Alkylation and Acylation Reactions of Amines