Polynuclear Hydrocarbons Preparations and Reactions

This presentation includes all the preparations and reactions of various Polynuclear hydrocarbons as naphthalene, Phenanthrene, anthracene,diphenylmethane,triphenylmethane and their derivatives.This is made by the b Pharmacy 2 year students of Gurunanak College of Pharmacy Nagpur as a group activity which focussed on student participation.

1. POLYNUCLEAR HYDROCARBONS (Synthesis and Reactions) Presented by- Parul Babhulkar Mariya Amravatiwala Kartik Kanugo Vinayak Laghate Vaishnav kore 2 nd year B.pharm, Gurunanak college of pharmacy, Nagpur Guided by: Prof. Pradyna Gondane

2. Classification:

3. Haworth Synthesis : Synthesis of Naphthalene : Benzene Succinic anhydride 3-Benzoyl propanoic acid ( Clemmenson Reduction) 4-phenyl butanoic acid - tetralone Tetralin Napthalene (for ring closure of acids, sulphuric,phosphoric,HF and PPA are commonly used as catalyst.)

4. 2. From 4-phenyl-3-enoic acid(Fitting reaction): Synthesis of Naphthalene:

5. 3. From 4-phenylbut-1-ene : Synthesis of Naphthalene :

6. Naphthalene is more reactive than benzene because it undergoes more easily oxidation, reduction,addition reactions, and electrophilic substitution reactions as compared to benzene. Oxidation of naphthalene : These are Various oxidation reactions of naphthalene. Chemical Reactions of Naphthalene:

7. 2. Reduction reactions of naphthalene : Chemical Reactions of Naphthalene:

8. 3. Addition reactions of naphthalene: Further dehydrohalogenation of these (di and tera ) napthalene halides results in the formation of substituted halo- napthalene derivatives which on oxidation gives pthalic acid. Chemical Reactions of Naphthalene:

9. In naphthalene electrophile attack preferably at C 1 position(-carbon).the various electrophilic substitution reactions are as follows: Nitration : nitration of naphthalene occurs at room temperature. Electrophilic substitution reactions of naphthalene :

10. b) Halogenation: c) Friedel -crafts Alkylation : It is carried out in mild conditions(low temp.) Electrophilic substitution reactions of naphthalene :

11. In case of naphthalene react with bromopropane yields 2-isopropyl naphthalene a the propyl cation formed during reaction rearranges to a more stable isopropyl cation . d) Friedel -crafts acylation :It depends upon nature of solvent used. Electrophilic substitution reactions of naphthalene:

12. e) Sulfonation : Electrophilic substitution reactions of naphthalene:

13. Orientation of Electrophilic substitution in Naphthalene: Naphthalene Nitration Nitronium ion (NO 2 + ) Halogenation Chloronium ion ( Cl + ) Halonium ion ( X +) α - position of Naphthalene + E + Electrophilic substitution reaction More preferable α -position β So, attack of electrophile can occur at α -position or β -position . α

14. Conjugated system Regular conjugation (alternate single-double bonds) More stable Cross conjugation (not a continuous chain) Less stable

15. As per Morrison:- Like benzene, the polynuclear hydrocarbon naphthalene typically undergoes electrophilic substitution which entitle it to be "aromatic ". Nitration and halogenation occur almost exclusively in the α -position. When we consider nitration, attack by nitronium ion at the α -position of naphthalene yields an intermediate carbocation that is a hybrid of structures I and II in which the positive charge is accommodated by the ring under attack, and several structures like III in which the charge is accommodated by the other ring.

16. Attack at the β-position yields an intermediate carbocation that is a hybrid of IV and V in which the positive charge is accommodated by the ring under attack, and several structures like VI in which the positive charge is accommodated by the other ring . In structures I, II, and IV, the aromatic sextet is preserved in the ring that is not under attack; these structures thus retain the full resonance stabilization of one benzene ring (36 kcal/ mol ). In structures like III, V, and VI, on the other hand, the aromatic sextet is disrupted in both rings, with a large sacrifice of resonance stabilization. Clearly, structures like I, II, and IV are much the more stable. But there are two of these stable contributing structures (I and II) for attack at the α -position and only one (IV) for attack at the β -position. On this basis we would expect the carbocation resulting from attack at the α -position (and also the transition state leading to that ion) to be much more stable than the carbocation (and the corresponding transition state) resulting from attack at the β -position, and that nitration would therefore occur much more rapidly at the α -position.    

17. Orientation of Electrophilic Substitution in Naphthalene Derivatives: Activating group (e ¯ releasing ) Further substitution Same ring 1 st position further substitution on 4 th position (and, to a lesser extent on 2 nd position). 2 nd position further substitution on 1 st position. For example:

18. Deactivating group (e - withdrawing) Further substitution other ring at α - position in nitration or halogenation. At α - or β - position (depending upon temperature) sulfonation . For example: These rules do not always hold in sulfonation , because the reaction is reversible and at high temperatures tends to take place at a β -position .

19. Naphthol Synthesis: i.Two types of naphthols (i.e.  or β - naphthol ) occurs in small quantities in coal tar. Derivatives of naphthalene:

20. ii.1-Naphthol can also be prepared by hydrolysis of 1-Napthylamine with sulfuric acid at 180 ◦ C. Derivatives of naphthalene:

21. Chemical reactions of naphthol : Naphthols undergo coupling reactions with benzene diazonium salts and forms azo dyes. - Naphthols gives violet color whereas β - Naphthol gives green color with ferric chloride solution. This reaction is used for quantitative estimation of  and β - naphthols . Derivatives of naphthalene:

22. Naphthylamines Synthesis :(a) From Naphthol ( Bucherer reaction): (b)From 1-Nitronaphthalene: Derivatives of Naphthalene :

23. Chemical reactions : (a)When 1-napthylamine is reacted with sulfuric acid it yiels naphthionic acid ,which is used in dye industry. (b) Diazonium salts of naphthylamine : Derivatives of Naphthalene:

24. The diazonium salt of naphthylamine can be used for preparation of other substituted naphthalene derivatives . Derivatives of Naphthalene:

25. Naphthanoic acid Synthesis (a)From Grignard Reagent: (b)By idoform reaction: Derivatives of Naphthalene:

26. (c) Kolbe Schmitt reaction: Derivatives of Naphthalene:

27. Naphthoquinones (1) 1,2-Napthoquinone Derivatives of Naphthalene:

28. (2) 1,4-Naphthoquinone Derivatives of Naphthalene:

29. (3)2,6-Napthoquinone- it is strong oxidising agent of all naphthoquinones . Chemical reaction of 1,4-Naphthoquinones: Derivatives of Naphthalene:

30. 1. Friedel-crafts reaction: i)From benzyl chloride: ii)From benzene and 1,1,2,2-tetrabromoethane: iii)From benzene and phthalic acid: Synthesis of Anthracene :

31. 2. Elbs reactions: by this methods anthracene is prepared by pyrolysis of o- methylbenzophenone . 3. Diels-Alder reactions: Synthesis of Anthracene :

32. a) Electophilic substitution reactions: Chemical reactions of anthracene :

33. (b) Diels-Alder reaction: Anthracene undergoes Diels-Alder reaction at 9,10 positions and forms endo-anthracene maleic anhydride. Chemical reactions of anthracene :

34. (c)Other reactions of anthracene : Chemical reactions of anthracene :

35. i) Anthrone : It is stable,colourless solid having m.p . 154 ◦ C.It is synthesized by heating anthranol . It can also be prepared by heating o- benzylbenzoic acid with HF. Derivatives of anthracene :

36. Or it may be prepared by reduction of anthraquinone with tin and HCl in glacial acetic acid. ii) Anthraquinone : Among the various isomeric quinones of anthracene only three isomers are well known i.e 1,2-,1,4- and 9,10. But only 9,10- compound is referred simply as anthraquinone . Derivatives of anthracene : HCl,CH 3 COOH

37. Synthesis of anthraquinone : (a) (b) Derivatives of anthracene :

38. Chemical reactions of Anthraquinone : 1) Reduction reactions : Derivatives of anthracene :

39. 2) Electrophilic substitution reactions : The outer rings of anthroquinone are aromatic in nature and capable for substitution reactions. But the presence of two electron withdrawing carbonyl groups deactivate the aromatic rings towards electrophilic substitution. However under vigrous conditions anthraquinone undergo nitration and sulfonation . Derivatives of anthracene :

40. Electrophilic substitution reactions:

41. iii) 2-Aminoanthraquinone : Synthesis The sodium arsenate oxidises the liberated sulphite which other wise would attack the amine product. Derivatives of anthracene :

42. Reactions of 2-Aminoanthraquinone: Derivatives of anthracene :

43. 1) Haworth Synthesis : Synthesis of Phenanthrene : 3(1-napthyol) propanoic acid 4-(1-napthyl) butanoic acid Cyclic ketone

44. 2) Pschorr synthesis : O- nitrobenzaldehyde is heated with sodium B- phenylacetate in the presence of acetic anhydride gives a-phenyl-o-nitro cinnamic acid (1) which is diazotised with NaNO ,/H.SO, followed by treatment with sulphuric acid and cop per powder phenanthrene-9-carboxylic acid is obtained (2). The compound (2) on strong heating give phenanthrene . Synthesis of Phenanthrene :

45. Chemical reactions of Phenanthrene :

46. Phenanthraquinone : It is an orange solid which is odorless and not steam volatile.It can be synthesized as follows: Derivatives of Phenanthrene :

47. Reactions of Phenanthraquinone : Derivatives of Phenanthrene :

48. 1. Friedel-Crafts condensation: 2. Condensation of Formaldehyde: Synthesis of Diphenyl Methane :

49. 3. From Grignard reagent: 4. Wolff-Kishner reduction : Synthesis of Diphenyl Methane:

50. Chemical Reactions of Diphenylmethane :

51. 1. Friedel-Crafts reaction : a) b) 2. Triphenylmethane can also be prepared by reacting the benzaldehyde with benzene in presence of ZnCl2 as catalyst. Synthesis of Triphenylmethane :

52. Chemical reactions of Triphenylmethane :

53. Thank You