1. 1 Jerry Poteat Science Department Georgia Perimeter College © John Wiley and Sons, Inc. Version 1.0 Chapter 25 Amides and Amines: Organic Nitrogen Compounds Hein * Pattison * Arena * Best

2. 2 Chapter Outline 25.1 Amides: Nomenclature and Physical Properties 25.2 Chemical Properties of Amides 25.3 Polyamides: Condensation Polymers 25.4 Urea 25.5 Amines: Nomenclature and Physical Properties 25.6 Preparation of Amines 25.7 Chemical Properties of Amines 25.8 Sources and Uses of Selected Amines

3. 3 25.1 Amides: Nomenclature and Physical Properties

4. 4 Amides are nonbasic (i.e. neutral) nitrogen-containing compounds. Amides are produced when a carboxylic acid is heated in the presence of ammonia.

5. 5 IUPAC Rules for Naming Amides 1. Name the longest continuous carbon chain containing the amide group. 2. Drop –ioc from the corresponding carboxylic acid and add the suffix –amide. For example,

6. 6 3. Use a capital N as the prefix if the amide nitrogen atom has an alkyl group as shown here. IUPAC Rules for Naming Amides

7. 7 Some amides have common names as shown here and in Table 25.1 in the next slide.

8. 8

9. 9 The physical properties of amides are determined largely by hydrogen bonding. Because of hydrogen bonding the melting points and boiling points are higher and the low molar mass amides are water-soluble. Figure 25.1 Examples of hydrogen bonding between (a) an amide and water and (b) between amide molecules.

10. 10 This table summarizes some of the physical properties of amides. Polarity Solubility M.P./B.P. Physical State/Appearance Polar Low molar mass amides are soluble in water Both m.p. & b.p. are high due to hydrogen bonding Colorless/odorless solids at room temperature except formamide. Property Description

11. 11 25.2 Chemical Properties of Amides

12. 12 Hydrolysis of Amides Acidic Hydrolysis Basic Hydrolysis An important reaction of amides is hydrolysis. Amides undergo acidic and basic hydrolysis producing a carboxylic acid or carboxylate salt.

13. 13 25.3 Polyamides: Condensation Polymers

14. 14 Polyamides Polyamides are condensation polymers that contain repeating amide linkages as shown here.

15. 15 Example of a synthetic polyamide Example of a biological polyamide Polyamides are either synthetic like Nylon-66 are biological like the enzyme chymotrypsin.

16. 16 25.4 Urea

17. 17 Urea Urea is a simple diamide that is excreted in urine. Urea is the metabolite the body uses to excrete toxic ammonia. The structure of urea is shown here. Urea is a white solid that melts at 133  C. It is very soluble in water

18. 18 Urea Commercial applications involving urea include fertilizer and the synthesis of plastics and barbiturates. An example of a synthesis using urea,

19. 19 25.5 Amines: Nomenclature and Physical Properties

20. 20 Amines are basic nitrogen-containing compounds that are derivatives of ammonia. Amines are classified as primary ( i.e. the nitrogen atom has one carbon atom attached ), secondary ( i.e. the nitrogen atom has two carbon atoms attached) and tertiary (i.e. the nitrogen atom has three carbon atoms attached) as seen below in these structures.

21. 21 IUPAC Rules for Naming Amines 1. Name the longest continuous carbon chain containing the amine group. 2. Drop –e from the corresponding alkane and add the suffix – amine. For example,

22. 22 3. Use a prefix with a capital N if the amine nitrogen atom has an alkyl group as shown here. IUPAC Rules for Naming Amines

23. 23 Some amines have common names as shown here.

24. 24 Heterocyclic Compounds Heterocyclic compounds are ring compounds which have two or more atoms in the ring that are different. O, N, and S are the most common heteroatoms. Many nitrogen based heterocyclic compounds like those shown below are found in DNA.

25. 25 Polarity Solubility M.P./B.P. Physical State/Appearance Polar Amines with six carbons or less are very soluble in water Both m.p. & b.p. are high due to hydrogen bonding Methyl and ethylamine are gases with strong ammonia-like odors, others are liquids with strong fishy odors Property Description This table summarizes some of the physical properties of amines.

26. 26 Amines are responsible for the strong odors of decaying flesh which are produced by bacterial decomposition. Two of these compounds are actually diamines as shown here.

27. 27 25.6 Preparation of Amines

28. 28 Preparation of Amines Amines are prepared by: 1. Alkylation of ammonia and amines 2. Reduction of amides 3. Reduction of nitriles 4. Reduction of aromatic nitro compounds

29. 29 Alkylation of Ammonia and Amines Four successive alkylations of ammonia eventually yields a quaternary ammonium salt.

30. 30 Reduction of Amides Lithium aluminum hydride reduces an amide to an amine

31. 31 Reduction of Nitriles Nitriles are reduced to amines using hydrogen gas and a metal catalyst

32. 32 Reduction of Aromatic Nitro Compounds Nitrobenzene is reduced to aniline which is a common aromatic amine.

33. 33 25.7 Chemical Properties of Amines

34. 34 Alkaline Properties of Amines Amines produce hydroxide ions in water just like ammonia.

35. 35 Alkaline Properties of Amines Amines are weak bases. For example, compare the pH of the following amines with the pH of ammonia. A 0.1M solution of NH 3 (ammonia) has a pH of 11.1 while CH 3 NH 2 is more basic at a pH of 11.8. However an aromatic amine like aniline is less basic at a pH of 8.8.

36. 36 Alkaline Properties of Amines Amines are much more basic than amides and the body uses this fact to convert toxic ammonia into urea as shown here.

37. 37 Alkaline Properties of Amines Amines also are a source of positive charges on biological molecules under physiological conditions. Dopamine and serotonin are typical examples of these amines.

38. 38 Salt Formation Because amines are weak bases, they react with strong acids to form ammonium salts. Methylamine for example reacts with strong acid yielding the methylammonium salt.

39. 39 Formation of Amides Amides are produced when primary and secondary amines react with acid chlorides.

40. 40 25.8 Sources and Uses of Selected Amines

41. 41 Amines and amides are found in the B-complex vitamins B 1 and B 3. Many antibacterial agents include nitrogen containing compounds such as those shown here.

42. 42 Alkaloids are a class of compounds derived from plants that show biological activity. Procaine is an example of a local anesthetic. An alkaloid like nicotine stimulates the nervous system while the opium alkaloids like methadone and cocaine have morphine-like activity ( i.e. sleep inducing and analgesic properties).

43. 43 Amphetamines are a class of compounds that stimulate the central nervous system. Amphetamines like methamphetamine mimics the action of epinephrine which produces a feeling of well-being and increased alertness.

44. 44 Barbiturates are a class of compounds that depress the central nervous system. These sedatives contain amide groups. An example is pentobarbital.

45. 45 Other examples of drugs containing the amine/amide functional groups include tranquilizers like Valium and antidepressants like Prozac.

46. 46 Chapter 25 Summary  Amides and amines are nitrogen-containing compounds.  Amides are nonbasic while amines are basic.  Amides are derivatives of RCOOH while amines are derivatives of NH 3.  Amides are odorless while amines tend to have strong disagreeable odors.  Urea is a diamide that the body uses to excrete toxic ammonia.  Amides are prepared by heating RCOOH in the presence of ammonia.

47. 47 Chapter 25 Summary  Amines are prepared by reducing amides, nitriles, and nitro compounds with reducing agents like LiAlH 4 and H 2 /Ni.  Polyamides are condensation polymers that are synthetic like Nylon-66 or biological polymers like proteins.  Amides and amines are found in a wide variety of compounds to include antibacterial agents, vitamins, and drugs.