Polynuclear hydrocarbons

By students of Sir Dr. M.S. GOSAVI COLLEGE OF PHARMACEUTICAL EDUCATION AND RESEARCH, NASHIK

1. POLYNUCLEAR HYDROCARBONS Group no:- 1 ROLL NO:-1 to 8 Guidance by:- Mrs.Smita saudagar Mam .

2. NAME OF PARTICIPANTS (GROUP –1) Roll number Name of the student 1 Nayan Aarote 2 Siddhi Avhad 3 Sujata Badhe 4 Sakshi Bagul 5 Tejas Bagul 6 Snehal Barve 7 Vivek Baviskar

3. INTRODUCTION:- A polycyclic aromatic hydrocarbon is a hydrocarbon-a chemical compound containing only carbon and hydrogen-that is composed of multiple aromatic rings. The group is a major subset of the  aromatic hydrocarbons . The simplest of such chemicals are naphthalene, having two aromatic rings, and the three ring compounds anthracene and phenanthrene.   Polynuclear hydrocarbons are uncharged, non-polar molecules, with distinctive properties due in part to the delocalized electrons in their aromatic rings. Polynuclear hydrocarbons are nonpolar and lipophilic and Larger Polynuclear hydrocarbons are generally insoluble in water, although some smaller Polynuclear hydrocarbons are soluble.

4. Five Polynuclear compounds to be covered in this chapter:- 1.Naphthalene. 2.Anthracene. 3.Phenanthrene. 4.Diphenyl methane. 5.Triphenyl methane.

5. 1) Naphthalene:- Molecular formula:-C10H8 Naphthalene, also known as naphthalin, bicyclo [4.4.0]deca-1,3,5,7,9-pentene Naphthalene has two carbon atoms shared by two rings. A naphthalene molecule is derived by the fusion of a pair of benzene rings, Unlike benzene, the carbon-carbon bonds in naphthalene are not of the same length.

6. Resonance of naphthalene:- 1. One structure has two identifiable benzene rings and the other two are 10 π-electron annulenes. 2. According to resonance theory,naphthalene is considered to be a hybrid of three form, An examination of these structures discloses that the bond between carbon-1 and carbon-2 has greater double bond character than the bond between carbon-2 and carbon-3. 3. 4.A naphthalene has a resonance stabilization energy per ring slightly less than that of benzene (36 kcal/mole),Hence the naphthalene is less aromatic than benzene. 5. Satisfy Huckel’s rule (4n+2) =(4*2+2)=10

7. Synthesis (Method of preparation) of Naphthalene 1.From petroleum:- When the petroleum fractions one passed over copper(Cu) catalyst at 680 C,Naphthalene and methylnaphthalenes are formed. Af ter this, methylnaphthalenes are separated and further converted into naphthalene by heating with hydrogen under pressure. 2)From 4-Phenyl-1-butene:- When 4-phenyl-1-butene is passed over red hot calcium oxide,naphthalene is obtained.

8. 3)From 4-phenyl-3-butanoic acid:- When 4-phenyl-3-butanoic acid is heated with concentrated sulphuric acid (H2SO4). on rearrangement 4-phenyl-3-butanoic acid Unstable Naphthalene 1-Naphthol

9. 4)By Haworth synthesis:- This reaction contains five steps:- Step-1 st ( Friedal -craft acylation) : - B enzene and succinic anhydride are heated in the presence of aluminium chloride to form 3 - Benzoyl propanoic acid. Step-2 nd ( Clemmensen reduction) :- 3-Benzoyl propanoic acid is treated with amalgamated zinc in the presence of hydrochloric acid(HCl) to give 4-Phenyl-3-butanoic acid.

10. Step 3 rd (Ring closure reaction) 4- phenyl-3-butanoic acid is heated with conc.H2SO4 or polyphosphoric acid to form α-tetralone. Step 4 th ( Clemmensen reduction) α- teralone is heated with amalgamated zinc and hydrochloric acid to give tetraline .

11. Step 5 th (Aromatization reaction) Tetraline is heated with palladium to yield naphthalene .

12. Physical properties of naphthalene 1.It is colourless crystalline solid. 2.Melting point:-82°C and Boiling point :-218°C. 3. Insoluble in water ,but soluble in ether,benzene , and not ethanol. 4.It has characteristics ‘Moth ball’odour .

13. 1.Nitration:- Naphthalene undergoes nitration with concentrated nitric acid in the presence of sulphuric acid at 60°C to produce 1-nitronaphthalene. 2.Friedal-craft acylation:- Naphthalene undergoes acylation with acetyl chloride and aluminium chloride in carbon disulphide to give the 1-acetyl naphthalene . Reactions of Naphthalene:-

14. 3.Friedal craft alkylation:- Naphthalene undergoes alkylation with alkyl halides in the presence of aluminium chloride to give 2-alkylnaphthalene(Methyl halides do not react) 4.Reduction:- Naphthalene undergoes reduction more readily than benzene ,when it react with sodium and ethyl alcohol) B.P 78 °C as it gives 1,4-dialin (1,4-dihydronaphthalene) .

15. 5.Oxidation:- Naphthalene is much more easily oxidized than benzene ,when it react with chromium trioxide in acetic acid at room temperature,it gives 1,4-naphthaquinone.

16. Medicinal uses of naphthalene:- 1.Naphthalene is used in manufacture of ‘moth balls’ to protect woolen goods,recently p-dichlorobenzene replaced it due to its obnoxious odour. 2.Used in manufacture of pthalic anhydride,carbonyl for insecticides. 3.Also used in dyes and several medicinal products.

17. Derivatives:- 1.Naphthols:- The hydroxyl derivatives of naphthalene. 2.Naphthylamines:- The amino derivatives of naphthalene.

18. 2)Anthracene:- Molecular formula:-C 14 H 10 Anthracene, also called paranaphthalene or green oil, a solid polycyclic aromatic hydrocarbon Anthracene is a solid polycyclic aromatic hydrocarbon and consisting of three fused benzene rings. It has SP2 hybridisation ,and the SP2 hybrid orbitals overlap with each other and with S orbital of the ten hydrogen atom forming C-C and C-H σ bonds.

19. Resonance of Anthracene:- 1. Anthracene will undergo delocalisation to give four resonance structures. 2. One structure has two identifiable benzene rings and the other three are 14 π-electron annulenes. 3.The presence of resonance structure makes anthracene a rigid,planar molecules stabilized by delocalization of electrons. 4. C1-C2 bond to have more double bond character (shorter bond length) and C2-C3 bond to have more single bond character (longer bond length). 5. It has a conjugated system and must follow (4n + 2) electrons with Huckel’s rule). 6.Resonance energy of anthracene is 84 kcal/mole(average 28 kcal/mole per ring,which is lower than benzene(36 kcal/mole) Hence,anthracene is much less aromatic than benzene.

20. Synthesis of Anthracene:- It involves the four different types of synthesis. 1 )By friedal craft reaction:- Benzene chloride reacts with itself to form 9,10-dihydroanthracene,which readily losses two hydrogen atoms to yield anthracene.

21. 2)By Haworth synthesis:- This involves the treatment of benzene with pthalic anhydride in the presence of aluminium chloride to form o- benzoylbenzoic acid,then o- benzoylbenzoic acid heated with concentrated sulphuric acid(H2SO4)to give 9,10-anthraquinone. Now,distillation of the anthraquinone with zinc dust yield anthracene.

22. 3)By Elbs reaction:- The conversion of a diaryl ketones containing a methyl or methylene group to the carbonyl function is known as the the Elbs reaction.

23. 4)By Diels-Alder reaction:- This involves the reaction of1,4-naphthaquinone with 1,3-butodiene. The product (Diels-Alder adduct) of this reaction is oxidized with chromium trioxide in glacial acetic acid to form 9,10-anthraquinone. Now,Distillationn of the anthraquinone with zinc dust yields anthracene.

24. Physical properties of anthracene 1.It is colourless solid. 2.Melting point:-218°C and Boiling point:-340°C 3. Anthracene is insoluble in water and dissolve in benzene. 4.It shows strong blue fluorescence when exposed to ultraviolet light. 5.This fluorescent property of anthracene is used in the criminal detection work,since a small amount of finely powdered anthracene on clothing,skin,money,etc.,is not detected under ordinary light but easily noticed when exposed to ultraviolet light.

25. 1)Nitration:- Anthracene react with concentrated nitric acid in acetic anhydride(H2SO4 not be used here)at room temperature to yield a mixture of 9-nitroanthracene and 9,10-dinitroanthracene. 2) Friedal craft acylation:- Anthracene undergoes acylation with acetyl chloride and aluminium chloride to form 9-acetylanthracene. Reactions of anthracene:-

26. 3)Reduction:- Anthracene undergoes reduction with sodium and ethyl alcohol to form 9,10-dihydroanthracene. 4)Oxidation:- Anthracene undergoes oxidation with sodium dichromate and sulphuric acid to 9,10-anthraquinone.

27. 5)Diels-alder reaction:- Anthracene undergoes a diels -alder reaction with maleic anhydride to yields the corresponding adduct.

28. Uses of anthracene:- 1.Anthracene is used in the manufacture of anthraquinones. 2.Anthraquinone is used in the manufacture of alzarin and several other dyes. 3.Used as a preservative in wood and used as an insecticide for crops. 4.Used in some drugs, Purgative drugs- Senna,Rhubarb,Cascara Dithrol :-Antifungal. 5.Anthraquinone are also used as anthracene agent.

29. Derivatives of Anthracene:- Most important derivative of anthracene is anthraquinone (9,10-anthraquinone),which is prepared by oxidation of anthracene.

30. 3)Phenanthrene Molecular formula:-C 14 H 10 Phenanthrene a polycyclic aromatic hydrocarbon (PAH) ,consisting of three fused benzene rings. Phenanthrene is an iosmer of anthracene. It may be obtained ,along with anthracene, from the green oil fraction of coal-tar. All the fourteen carbon atoms are SP2 hybridized. The SP2 hybridised orbitals overlap with each other and S-orbital of ten hydrogen atom to form C-C and C-H σ bonds. All these( Anthracene,naphthalene,phenanthrene ) are aromatic and follow huckle rule.

31. Resonance of Phenanthrene:- 1. The tricyclic aromatic hydrocarbon phenanthrene has substantial resonance stabilization, 2.One of the five contributing structures has three fused benzene ring moieties, two of the structures have a benzene ring fused to a 10 π-electron annulene, and the remaining two are 14 π-electron annulenes, which are aromatic by the Hückel Rule. 3. C9-C10 bond to have more double bond character, Other carbon-carbon bonds have varying bond order, as reflected in the bond lengths shown on the right hand structure.

32. Synthesis of Phenanthrene:- It is obtained by Haworth synthesis :- 1) Friedal craft acylation:- This involves the treatment of naphthalene with succinic anhydride in the presence of aluminium chloride to form Naphoylpropionic acid.( Friedal craft acylation)

33. 2) Clemmensen reduction:- Then,Naphthoylpropionic acid treated with amalgated zinc in the presence of Hydrochloric acid(HCl) to give Naphthylbutyric acid.

34. 3)Ring closure reaction:- Now,Naphthylbutyric acid heated with H2SO4 to give 1-keto1,2,3,4-tetrahydrophenanthrene. H2SO4

35. 4) Clemmensen reduction:- In this 1-keto1,2,3,4-tetrahydrophenanthrene is treated with amalgamated zinc in the presence of HCl to give1,2,3,4-Tetrahydrophenanthrene. zn HCl 5)Now,1,2,3,4-Tetrahydrophenanthrene heated with palladium to yield phenanthrene.

36. From Dibenzyl:- Phenanthrene can be obtained by passing dibenzyl through a red hot tube . From 2,2-Dimethyl-diphenyl:- Phenanthrene can also be obtained by cyclodehydrogenation of 2,2-Dimethyl-diphenyl using sulphur.

37. Physical properties of phenanthrene:- 1.It is a colourless solid. 2.Melting point 100°C. 3.It is insoluble in water,but dissolve readily in ethanol,benzene and ether.

38. Reactions of Phenanthrene:- It undergoes oxidation,reduction,addition and electrophillic substitution reaction. As with anthracene these reactions preferentially occur at the C-9 and C-10 position. 1) Friedal craft acylation:- Phenanthrene undergoes acylation with acetyl chloride in the presence of aluminium chloride at 0°C to give 9-acetylphenanthrene.

39. 2)Nitration:- Phenanthrene undergoes nitration with concentrated nitric acid and sulphuric acid to yield 9-nitrophenanthrene. 3)Reduction:- Phenanthrene undergoes reduction with sodium and isopentanol to form 9,10-dihydrophenthrene.

40. 4)Oxidation:- Phenanthrene undergoes oxidation with potassium dichromate and sulphuric acid in acetic acid to form 9,10-phenanthraquinone.Further oxidation of this with hydrogen peroxide in acetic acid give diphenic acid.

41. Uses of phenanthrene:- 1.It is used to make dyes,plastic and pesticides,also used in explosives and drugs. 2.Also,used to make bile acids,cholestrol and steroids.

42. 4)Diphenyl methane:- Molecular formula:-(C 6 H 5 ) 2 CH 2 Diphenylmethane is an organic compou nd, consists of methane where in two hydrogen atoms are replaced by two phenyl groups . The diphenylmethyl group is also known as benzhydryl .

43. Synthesis of Diphenyl methane:- 1) Friedal -crafts reaction:- Diphenyl methane is prepared by friedal -craft condensation between benzyl chloride and benzene. 2)From benzene:- Diphenyl methane is also prepared from two moles of benzene and dichloromethane in the presence of aluminium chloride.

44. 3)From benzophenon :- Diphenyl methane is prepared from benzophenon,which is reduced in the presence of red hot phosphorous and hydroiodic acid. 4)From Grignard reagent:- Diphenyl methane is prepared by grignard reagent.

45. Reactions of Diphenyl methane:- 1)Nitration:- Diphenyl methane is the presence of concentrated sulphuric acid gives bis(4-nitrophenyl) methane. 2)Halogenation:- Diphenyl methane in the presence of bromine and UV light gives diphenyl methyl bromide.

46. 3)Oxidation:- Diphenyl methane upon oxidation in presence of potassium dichromate and sulphuric acid gives benzophenon . 4)Cyclization:- When diphenyl methane is heated it gives 9H-fluorene.

47. Physical properties:- 1.It is a colourless oil. 2.Melting point:-22-24°C and Boiling point:-264° Uses:- It is used in the synthesis of methylene diphenyl diisocynate,which is used in the manufacture of polyurethane and as an industrial strength adhesive.

48. 5)Triphenyl Methane Molecular formula:-(C₆H₅)₃CH Triphenylmethane is a triarylmethane in which the three aryl groups are phenyl. It forms the basic skeleton of several synthetic dyes .

49. Synthesis of Triphenyl methane:- 1) Friedal craft reaction:- It is prepared by the condensation between benzyl chloride and benzene. 2)The condensation between benzene and chloroform gives triphenyl methane.

50. 3)The condensation between benzaldehyde and benzene also gives triphenyl methane.

51. Reactions of triphenyl methane:-

52. Physical properties of triphenylmethane . 1. It is a colourless liquid. 2.Melting point :-92-94°C and Boiling point:-359°C . Uses:- 1.Triephenyl methane is a triarylmethane compound used as backbone of synthetic dyes. 2.Triphenyl methane has also been shown to inhibit 3-methylchloroethane-induced neoplastic transformation of loti cells.

53. Thank you…!!!