preparation and reaction of naphthalene

1. Polynuclear hydrocarbon

2. Type
The rings are
isolated
• Diphenyl
methane
• Triphenyl
methane
The rings are fused
together in the
ortho position
• Naphthalene
• Anthracene
• Phenanthrene

4. Structure of naphthalene

7. • All ten carbons are sp2 hybridized
• Overlap of Sp2 With s orbital's of 8 hydrogen
atom.
• All carbon and hydrogen lying in one plane.
• It is confirmed by X ray diffraction studies.
• It is aromatic satisfies the Huckle’s rule
• It is less aromatic than benzene.

9. Naphthalene
• It is the largest constituent of Coal tar
• It is obtained by cooling middle and Heavy oil
• The crude naphthalene is melted and treated
with sulphuric aicid to remove basic impurities.
• Washed with water.
• Treated with aqueous sodium hydroxide to
remove acidic impurities.
• Finally naphthalene is distilled to give pure
product.

10. Resonance hybrid of naphthalene

11. Structure of naphthalene
• Erlenmeyer proposed the symmetrical formula
for naphthalene in 1866

12. Graebe proved that it did consist of
two benzene rings fused together in
the ortho position in 1869

13. Naphthalene on oxidation gives
phthalic acid

14. •When nitrated naphthalene gives nitro
naphthalene which, on oxidation , gave o-
nitro phthalic acid.
This indicates that nitro group is in
benzene ring and that it is the side chain
which are oxidised.

15. Nitro naphthalene reduced give amino
naphthalene oxidised, phthalic acid was
obtained.
An amino group attached to the nucleus
renders sensitivity to oxidation,

16. Inference: benzene ring in phthalic acid
obtained by oxidation of amino
naphthalene is not the same ring as that
originally containing nitro group in nitro
naphthalene
i.e naphthalene contains two benzene ring

17. Synthesis of Naphthalene

20. O-xylene bromide combines with disodioethane
tetra carboxylic ester when refluxed in acid
solution, gives tetrahydronaphthalene
dicarboxylic acid. When the silver salt of this
acid is heated, naphthalene is formed

23. Position of double bond in
naphthalene

24. Fries rule
• Fries compared the double bonds present in
polynuclear compounds with benzoquinone.
• Structure II and III have structure similar to
benzoquinone.
• Quinones are reactive than pure aromatic
compound.
• Fries belived that stable form of polynuclear
compound did not have this quinone
structure.

25. Fries rule
• The most stable form of polynuclear aromatic
compound is that form which has maximum
number of benzenoid ring i.e three double
bonds in each individual ring.
• According to fries naphthalene has structure I
[ has two benzenoid ring] and not the
structure of II and III [ has one benzenoid ring]

27. Reaction of naphthalene

28. Number of reduced product depend
on the reducing agent used. If sodium
in ethanol is used it gives 1:4 dialin
m.p is 28C
Naphthalene
Na
Ethanol
1:4 Dialin
1:4 dialin is unstable isomerise to form 1:2 dialin which also unstable to form
naphthalene in the presence of sodium ethoxide

29. • When reduced with isopentanol it forms
tetralin mp 206-208ᵒC.
• Tetralin is used as varnishes.

30. When naphthalene is reduced in the
presence of nickel it forms tetralin
then it gives decalin

31. Naphthalene get oxidised in the
presence of sulphuric acid,vanadium
pentoxide,mercuric sulphate or air to
phthalic anhydride.

32. Naphthalene on oxidation in presence
of permanganate gives phthalic acid

33. Naphthalene on ozonolysis yield
phthaldehyde

34. ozonolysis

35. Substitution product of naphthalene
• Orientation in naphthalene nucleus is more
complicated than benzene nucleus due to
presence of two rings in former.
• First group always enter the first position
except in two cases when second derivative is
the main product.
• Sulphonation at higher temperature
• Friedel craft reaction.

36. • Introduction of second substituent can give
rise to homonuclear substitution [ substitution
in the same ring] or heteronuclear
substitution [ second substitution in another
ring]

37. Homonuclear substitution occur only when
group already present is ortho para directing

38. • Self polarisability is greater at position I than
in position II in case of naphthalene.
• Self polarisability position and larger
magnitude of self polarisability, the more
reactive will be that point for the electrophillic
reagent.
• Pie electron density is greater in 1:2 than 2:3
therefore former will be more reactive than
the later.

39. Friedel craft reaction
• Naphthalene nucleus is attacked by aluminum
chloride when vigorous conditions are used.
• Lower temperature is maintained to carry out the
friedel craft reaction.
• Introduction of acyl group in presence of
aluminium chloride gives 1 and 2 ketones, the
nature of the solvent affects the yield.
• Acetyl chloride in carbondisulphide gives
compound 1 and 2 in the ratio 3:1 and with
nitrobenzene it is 1:9

41. Chloromethylation of naphthalene-
Paraformaldehyde,HCl, phosphoric
acid,Glacial acetic acid

43. Nitro naphthalene
• Nitric acid attacks naphthalene at room
temperature to form 1 nitro naphthalene.
• Nitration of naphthalene at higher
temperature give a mixture of 1:5 and 1:8
dinitro derivative.
• 2 nitro naphthalene is prepared by heating 2
naphthalene diazonium boro fluoride with
sodium nitrite and copper powder.

44. Naphthalene sulphonic acid

45. • When naphthalene is treated with
concentrated sulphuric acid at 40C gives the I
derivative and at 160C it yields II derivative.
• Βeta naphthalene sulphonic acid is the
starting material for all beta naphthalene
derivatives

46. Naphthyl amine

49. Reaction of naphthalene

50. • Colourless cyrstal
• Mp 82 C
• Boil at 217 C