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Polynuclear Hydrocarbons

Polynuclear Hydrocarbons. Classification of Polynuclear Hydrocarbons Polynuclear Hydrocarbons may be divided into two groups,. Polynuclear Hydrocarbons Benzenoid Non- Benzenoid. Isolated Fused rings. Linear Angular.

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Polynuclear Hydrocarbons

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  1. Polynuclear Hydrocarbons

  2. Classification of Polynuclear HydrocarbonsPolynuclear Hydrocarbons may be divided into two groups,

  3. Polynuclear Hydrocarbons Benzenoid Non- Benzenoid Isolated Fused rings Linear Angular

  4. Isolated Ring Polynuclear HydrocarbonsBiphenyl (diphenyl):

  5. a) Fittig reactionb) From benzene diazonium sulphate c) From benzidine Preparation of Biphenyl

  6. d) Ulmann diaryl synthesis e) By using Arylmagnesium halide

  7. Reactions of biphenylBiphenyl undergoes substitution reactions,

  8. In biphenyl one ring act as electron donating group and the other act as electron withdrawing group

  9. Resonance shows that O- and P- are the most reactive positions towards electrophilic substitution.The electrophilic substitution occurs in 4- position (major) and 2- position (minor) due to steric effect of other benzene ring.The 2nd substitution occurs in the empty ring in 2 or 4- position.e.g.

  10. Problem:Explain the products formed when biphenyl is mononitrated and when it is dinitrated.

  11. Biphenyl derivatives (1) Benzidine (4, 4`-diaminobiphenyl) (2) Diphenic acid (3) Diphenyl methane

  12. Benzidine (4, 4' diaminobiphenyl) Methods of preparation

  13. From dihydrazo benzene

  14. Q. Show how could you prepare benzidine from benzene? • Answer

  15. Uses of Benzidine • preparation of Congo red

  16. (2) Diphenic acid Methods of preparation

  17. From anthranilic acid

  18. Ulmann diaryl synthesis

  19. oxidation of Phenanthrene or phenanthraquinone

  20. Chemical Reactions

  21. 1. with acetic anhydride

  22. 2. Conversion of diphenic acid to dflourenone

  23. 3. with conc. H2SO4

  24. 4. Oxidation of KMnO4

  25. 5. with sodalime

  26. Atropisomers of biphenyl • Optical isomers produced due to restricted rotation is called atropisomers • Restricted rotation produce when 0- position contains two different bulky groups and hence molecule is optically active.. for example

  27. When o- position contains two similar groups, the molecule is optically inactive due to presence of plane of symmetry .. for example

  28. (3) Diphenyl methane Methods of preparation

  29. 1. Friedel- Crafte

  30. 2. From benzophenone

  31. Chemical Reactions

  32. 1. Nitration

  33. 2. Halogenation

  34. 3. Oxidation

  35. II. Fused System

  36. a) Naphthalene

  37. Structure elucidation of naphthalene 1- Molecular Formula: C6H8 2- So naphthalene contain the skeleton

  38. 3- So nitro group is present in benzene ring

  39. 4- The benzene ring in phthalic acid produced by oxidation of aminonaphthalene is not the same ring is that obtained by oxidation of nitronaphthalene.

  40. i.e. Naphthalene contains two benzene rings and we can explain this by this equation

  41. The structure of naphthalene is confirmed by method of its analysis 1- Howarth method

  42. Other way of cyclization

  43. The reaction occurs if R is o- or p- directing group such as NH2, NHR, OH, OR, R, halogen. • If R is m- directing group (e.g. NO2, CN, COOH, COCH3, SO3H) no reaction occur. • The above reaction gives  -substituted naphthalene.

  44. Synthesis of 1-alkyl naphthalene

  45. 2- From -benzylidene – propenoic acid

  46. Chemical Reactions of naphthalene

  47. 1. Reduction

  48. 2. Oxidation

  49. 3. Addition of Cl2

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