Chapter 9 amine

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  • Chapter 9 amine

    1. 1. ORGANIC CHEMISTRY II CHM301 AMINES 1 NURUL’ AIN BINTI JAMION
    2. 2. INTRODUCTION  Amines are similar to ammonia (base) with one or more alkyl groups bonded to the nitrogen atom. H  The classification: N H Ammonia H  1o, 2o, or 3o corresponding to the number of hydrogen atoms or alkyl replaced.  General structure: R N H H R N R' R'' R N R' H 2
    3. 3. OH NH N N CH3 H3C Cl Hydroxychloroquine  Identify whether the amino group shown by the arrow is primary, secondary or tertiary. 3
    4. 4. 4
    5. 5. NOMENCLATURE OF AMINES Count the carbons in the longest chain containing the amine  Drop the –e ending for the parent name and add –amine  For a secondary amine an N prefixes the compound giving the shorter carbon chain its side chain prefix name  For a tertiary amine an N,N prefixes the compound giving the two shorter carbon chains their side chain prefix names  Structural Formula H H C N H H H H H H C C N CH3 H H H H H H C C N CH3 H H CH3 Condensed Structural Formula CH3NH2 CH3CH2NHCH3 CH3CH2N(CH3)2 CA format methanamine N-methylethanamine 5 N,N-dimethylethanamine
    6. 6. NOMENCLATURE OF AMINES Aromatic amines belong to specific families, which act as parent molecules.  For example, an amino group (—NH ) attached to benzene 2 produces the parent compound aniline.  phenylamine 6
    7. 7. NOMENCLATURE OF AMINES  The prefix ‘amino’ is used to indicate the presence of an –NH2 group in a molecule containing more than one functional group. 1 1 7
    8. 8. NOMENCLATURE OF AMINES  Compounds with two –NH2 groups are named by adding the suffix ‘diamine’ to the name of the corresponding alkane or aromatic compounds. H2N (CH2)6 NH2 hexane-1,6-diamine (1,6-hexanediamine) H 2N NH2 benzene-1,4-diamine (1,4-benzenediamine) 8
    9. 9. PREPARATION OF AMINES 1. 2. 3. 4. 5. Reduction of nitro compounds Reduction of halides with ammonia Reduction of amides Reduction of nitriles Hoffmann degradation of amides 9
    10. 10. PREPARATION OF AMINES 1. Reduction of nitro compounds – gives 1o amines    Aromatic amines are normally prepared by reduction of the corresponding aromatic nitro compound. Aniline is prepared from nitrobenzene. Reducing agents: Fe/H+, Sn/H+ or catalytic hydrogenation (example, H2/Pd or Pt or Ni). 10
    11. 11. PREPARATION OF AMINES  Another example: 11
    12. 12. PREPARATION OF AMINES 2. Reduction of halides with ammonia  The reaction of ammonia with an alkyl halide leads to the formation of a primary amine.  The primary amine that is formed can also react with the alkyl halide, which leads to a disubstituted amine.(2o amine) 12
    13. 13. PREPARATION OF AMINES  Further reaction can form a trisubstituted amine.(3o amine).  In general: 13
    14. 14. PREPARATION OF AMINES 3. Reduction of amides  Amides yield primary amines on reduction by lithium aluminum hydride, LiAlH4.  The oxygen atom is replaced by two hydrogen atoms. 2o and 3o amides produce 2o and 3o amines, respectively. Reaction occurs via nucleophilic acyl substitution then nucleophilic addition.   14
    15. 15. PREPARATION OF AMINES 4. Reduction of nitriles   Nitriles can be reduced by strong reducing agent like H2 with catalyst (example Ni) or LiAlH4 to yield primary amines via nucleophilic addition reaction. Example: 2H2, catalyst R CN R CH NH or LiAlH4, ether 2 2 15
    16. 16. PREPARATION OF AMINES 5.    Hoffmann degradation of amides Heating the amides with a mixture of bromine and KOH or NaOH. amides will change to amines. is used to shorten the chain by one carbon. ∆ 16
    17. 17. REACTION OF AMINES 1. 2. 3. 4. 5. Formation of amides Amine alkylation: formation of quarternary salts With nitrous acid Isocyanides (nitrile compound) Benzenediazonium salts 1. Preparation of Benzenediazonium chloride 2. Reaction of Benzenediazonium chloride 17
    18. 18. REACTION OF AMINES 1. Formation of amides a. From acyl chlorides Addition of 1o , 2o (or ammonia) to acid chlorides results in amides. 18
    19. 19. REACTION OF AMINES  Example: 19
    20. 20. REACTION OF AMINES Formation of amides 1. a. From acid anhydride O R C O C R acid anhydride O R C O O O 2RNH2 R O 2R2NH R C O RNH3 + amide amine O C R C NHR O R C NR2 O + R C O R2NH2 20
    21. 21. REACTION OF AMINES Formation of amides 1. From ester Esters reacts with ammonia, primary and secondary amines to produce amides and alcohols. a. O R C O R ester C O R ester R H N R C NH primary amine secondary amide R R OH O R O R O R H R H N R secondary amine C N R R OH tertiary amide EXAMPLE O H3C C O CH2CH3 H H N H O O 0-5 C H3C C NH2 CH3CH2 OH 21
    22. 22. REACTION OF AMINES 2. Amine alkylation: formation of quarternary salts  Reaction of amines and acid will give amine salt (an ammonium ion). CH3CH2NH2 + HCl  CH3CH2NH3+ + Cl - CH3CH2CH2 NH2 HCl n-propylammonium chloride n-propylamine (CH3CH2)3 N triethylamine CH3CH2CH2 NH3Cl HCl (CH3CH2)3 NH Cl 22 triethylammonium chloride
    23. 23. REACTION OF AMINES  Amine alkylation: formation of quarternary salts  Examples: CH3CH2CH2 NH2 HCl n-propylammonium chloride n-propylamine (CH3CH2)3 N triethylamine CH3CH2CH2 NH3Cl HCl (CH3CH2)3 NH Cl triethylammonium chloride 23
    24. 24. REACTION OF AMINES 3. With nitrous acid  Nitrous acid is unstable and must be prepared in the reaction solution by mixing sodium nitrite with acid.  Primary amines react with nitrous acid to yield a diazonium salt, which is highly unstable and degradates into a carbocation that is capable of reaction with any nucleophile in solution. Therefore, reacting primary amines with nitrous acid leads to a mixture of alcohol, alkenes, and alkyl halides. 24
    25. 25. REACTION OF AMINES  With nitrous acid  Primary aromatic amines form stable diazonium salts at zero degrees. 25
    26. 26. REACTION OF AMINES  With nitrous acid  Secondary aliphatic and aromatic amines form nitrosoamine (yellow oils) with nitrous acid. 26
    27. 27. REACTION OF AMINES  With nitrous acid  Tertiary amines react with nitrous acid to form N-nitrosoammonium compounds (ammonium salts). 27
    28. 28. REACTION OF AMINES  Reaction of nitrous acid with aliphatic amines in cold acidic solution can be used to distinguish between primary, secondary and tertiary amines. RNH2 + HNO2 → N2 gas evolution from a clear solution. (1° amines) R2NH + HNO2 → An insoluble yellow oil formed (N-nitrosoamine) (2° amines) R3N + HNO2 → A clear solution (ammonium salt formation) (3° amines) 28
    29. 29. REACTION OF AMINES Isocyanides (nitrile compound) 4. Primary amines heated with trichloromethane (CHCl3) and alcoholic KOH solution will produce a foul odor of isocyanide, RNC. • Isocyanide: - an organic compound with functional group R N C - The CN functionality is connected to the organic fragment via the nitrogen atom, not via carbon atom. - a zwitterion (nitrogen atom carries positive charge, carbon atom carries negative charge). • 29
    30. 30. REACTION OF AMINES 4. Isocyanides (nitrile compound) examples: 30
    31. 31. REACTION OF AMINES 5. Benzenediazonium salts 1. Preparation of Benzenediazonium chloride  Structure • has the formula C6H5N2+Cl¯ • a diazonium group is attached to the benzene ring • the aromatic ring helps stabilise the ion 31
    32. 32. REACTION OF AMINES 5. Benzenediazonium salts 1. Preparation of Benzenediazonium chloride  From phenylamine (which can be made by reduction of nitrobenzene)  Reagents: nitrous acid and hydrochloric acid  Conditions: keep below 10°C  Equation: C6H5NH2 + HNO2 + HCl  C6H5N2 + Cl¯+ 2H2O  32
    33. 33. REACTION OF AMINES 5. Benzenediazonium salts 2. Reaction of Benzenediazonium chloride  Diazonium salts of aromatic amines are very useful as intermediates to other compounds.  Aromatic diazonium salts are only stable at very low temperatures (zero degrees and below), warming these salts initiates decomposition into highly reactive cations.  These cations can react with any anion present in solution to form a variety of compounds. Figure illustrates the diversity of the reactions. 33
    34. 34. REACTION OF AMINES 5. Benzenediazonium salts 2. Reaction of Benzenediazonium chloride • The nitrogen gas is released. 34

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