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

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

6. 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.

7.  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

8. ❖ Synthesis (Method of preparation) of Naphthalene
1.From petroleum:-
● When the petroleum fractions one passed over copper(Cu) catalyst at
6800C,Naphthalene and methylnaphthalenes are formed.
After 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.

9. 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

10. 4)By Haworth synthesis:-
This reaction contains five steps:-
❑ Step-1 st (Friedal-craft acylation): -Benzene 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.

11. ❑ 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.

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

13. • 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.

14. 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:-

15. 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).

16. 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.

17. • 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.

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

19. 2)Anthracene:-
 Molecular formula:-C14H10
 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.

20.  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.

21. ❖ 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.

22. 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.

23. 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.

24. 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.

25. ❖ 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.

26. 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:-

27. 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.

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

29. ❖ 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.

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

31. 3)Phenanthrene
● Molecular formula:-C14H10
● 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.

32.  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.

33. ❖ 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)

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

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

36. 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.

37. ● 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.

38. ❖ 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.

39. ❖ 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.

40. 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.

41. 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.

42. ❖ 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.

43. 4)Diphenyl methane:-
 Molecular formula:-(C6H5)2CH2
 Diphenylmethane is an organic compound,
consists of methane where in two hydrogen
atoms are replaced by two phenyl groups.
 The diphenylmethyl group is also known as
benzhydryl.

44. ❖ 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.

45. 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.

46. ❖ 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.

47. 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.

48. ❖ 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.

49. 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.

50. ❖ 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.

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

52.  Reactions of triphenyl methane:-

53. ❖ 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.

54. Thank you…!!!