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AMINES, AMIDES and ANILINE

AMINES, AMIDES and ANILINE. Amines. An amine is a base as well as a nucleophile. Some amines are heterocyclic compounds (or heterocycles). Most drugs, vitamins, and many other natural products are heterocycles. A natural product is a compound synthesized by a plant

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AMINES, AMIDES and ANILINE

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  1. AMINES, AMIDES and ANILINE

  2. Amines • An amine is a base as well as a nucleophile • Some amines are heterocyclic compounds • (or heterocycles) • Most drugs, vitamins, and many other natural products • are heterocycles • A natural product is a compound synthesized by a plant • or an animal

  3. Organic bases are amines Amines are derivatives of ammonia N 1s2, 2s2 2p1 2p1 2p1----------- lone pair occupies an sp3 orbital

  4. Amines are bases because of the lone pair on the nitrogen atom -red litmus paper to blue

  5. The lone-pair electrons on nitrogen allows an amine to turn “inside out” rapidly at room temperature

  6. Some Common Amines 1,4-butanediamine Both upper amines are 1o This amine is 1o This amine is 3o This amine is are 2o

  7. Aniline can be converted into useful diazonium salt

  8. HF H2O RCH2OH NH3 pKa = 3.2 pKa = 15.5 pKa = 36 pKa = 15.7 Relative Reactivity of Amine most reactive least reactive RCH2F > RCH2OH ~ RCH2OCH3 > RCH2NH2 The leaving group of a protonated amine cannot dissociate to form a carbocation or be replaced by a halide ion

  9. nucleophilic substitution reactions nucleophilic acyl substitution reactions Reactions of Amines

  10. Oxidation of Amines oxd oxd oxd a nitroso compound ahydroxylamine

  11. + H – •• •• •• •• •• •• O O N O N O H •• •• •• •• •• + H H H + •• •• •• •• + O N O O N O •• •• •• •• •• + H H Nitrite Ion, Nitrous Acid, and Nitrosyl Cation

  12. •• •• •• N O (CH3)2NH (CH3)2N •• Example CH3NH2+HNO2 CH3OH+N2+H2O NaNO2, HCl •• H2O (88-90%)

  13. + •• •• •• •• N N N O N O •• •• •• + H + H •• •• + N N O •• •• + H Nitrosation of Secondary Alkylamines • nitrosation of secondary amines gives an N-nitroso amine

  14. + fast + + R N2 RN N + slow + + N ArN Ar N2 Nitrosation of Primary Arylamines • gives aryl diazonium ions • aryl diazonium ions are much more stable thanalkyl diazonium ions • most aryl diazonium ions are stable under the conditions of their formation (0-10°C)

  15. NH2 (CH3)2CH NaNO2, H2SO4 H2O, 0-5°C + N (CH3)2CH N Example: HSO4–

  16. Cl Br Ar Ar F Ar CN Ar + N N Ar H I Ar Ar OH Ar Transformations of Aryl Diazonium Salts

  17. + + H N N N N Ar' Ar Ar Ar' an azo compound Ar' must bear a strongly electron-releasing group such as OH, OR, or NR2. Azo Coupling • Diazonium salts are weak electrophiles. • React with strongly activated aromatic compounds by electrophilic aromatic substitution.

  18. OH + N C6H5N OH N NC6H5 Example + Cl–

  19. Amides ------------- Not acids or bases • Features of a Peptide Bond • Usually inert • Planar to allow delocalisation • Restricted Rotation about the amide bond • Rotation of Groups (R and R’) attached to the amide bond is relatively free

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