2. Electrophilic substitution
Lab 1
Electrophilic substitution

3. Electrophilic substitution
chemical reactions in which an electrophile displaces a group in a compound, typically but not always hydrogen.

4. Electrophilic substitution
Electrophilic aromatic substitution
Electrophilic aliphatic substitution

5. electrophilic aliphatic substitution
chemical reactions in which an electrophile displaces a functional group in aliphatic compounds.
Mechanism of reaction:
two electrophilic reaction mechanisms
SE1 and SE2

6. electrophilic aliphatic substitution
SE1
course of action the substrate first ionizes into a carbanion and a positively charged organic residue. The carbanion then quickly recombines with the electrophile.
SE2
single transition state in which the old bond and the newly formed bond are both present.

7. electrophilic aliphatic substitution
Nitrosation
Ketone halogenation
Keto-enol tautomerism
aliphatic diazonium coupling
carbene insertion into C-H bonds

8. Electrophilic aromatic substitution
atom appended to the aromatic ring, usually hydrogen, is replaced by an electrophile.
Type
Nitration
halogenation
sulfonation
acylation and alkylating Friedel-Crafts reactions.

9. Friedel-Crafts alkylation
Halogination
Nitration
sulfonation
Friedel-Crafts alkylation
Friedel-Crafts acylation

10. Mechaniism of EAS: arenium ions
Step 1
Arenium ions
(nonaromatic cyclohexadienyl cation)

11. Mechaniism of EAS: arenium ions
Step 2
The proton is removed by any of the bases, for example by the anion derived from the electrophile

12. Halogenation of benzene
Benzene does not react with Br2 or CL2 unless a Lewis acid is present in mixture
Lewis acid is an electron-pair acceptor
Lewis acids most commonly used to effect bromination and chlorination reactions are FeCl3,FeBr3 and AlCl3

13. Bromonation of benzene

14. Electrophilic Aromatic Bromination
Step 1
Bromine combines with FeBr3 to form acomplex that dissocates to form apostive bromine ion and FeBr4-
Step 2
Arenium ions
Postive bromine ion is attacked by benzen to form an arenium ion

15. Electrophilic Aromatic Bromination
Step 3
Proton is removed from the arenium ion to become bromobenzene

16. Nitration of Benzene

17. Nitration of Benzene
Step 1
Step 2

18. Nitration of Benzene Step 3 Step 4
Arenium ions
The nitronium ion is the actual electrophile in nitration ; it reacts with benzene to form a resonance-stabilized arenium ion
Step 4
The arenium ion then loses a proton to a Lewis base and becomes nitrobenzene

19. Sulfonation of benzene
Benzenesulfonic acid

20. Sulfonation of benzene
Benzene react with fuming sulfuric acid at room temperature to produce benzensulphonic acid
Fuming sulfuric acid is sulfuric acid that contain added sulfur trioxide (SO3)
Sulfonation can takes place in conc sulfuric acid, alone but more slowly

21. Sulfonation of benzene

22. Sulfonation of benzene
Step 1
Step 2
SO3,is the actual electrophile that reacts with benzene to form an arenium ion

23. Sulfonation of benzene
Step 3
Step 4

24. Friedel-Crafts Alkylation

25. Friedel-Crafts Alkylation
Mechanism for reaction start with formation of carbocation (step 1 )
The carbocation then act as an electrophile and attack benzene ring to form an arenium ion (step 2)
The arenium ion then loses a proton to generate alkylbenzene (step 3)

26. Friedel-Crafts Alkylation
Step 1 +
Step 2

27. Friedel-Crafts Acylation
Friedel-Crafts Acylation reaction is mean introducting an acyl group into aromatic ring
Two common acyl groups are acetyl group and benzoyl group
benzoyl group
acetyl group

28. Friedel-Crafts Acylation
The reaction is carried out by treating the aromatic compound with acyl halide( often an acyl chloride)
The reaction requires the addition of a Lewis acid (such as AlCl3 )
The product of reaction is an aryl ketone.

29. Friedel-Crafts Acylation
Step 1
Acyl halide
Step 2
Acylium ion

30. Friedel-Crafts Acylation
Step 3
The acylium ion, acting as an electrophile, reacts with benzene to form the arenium ion
Step 4
A proton is removed from the arenium ion, forming the aryl ketone

31. Friedel-Crafts Acylation
Step 5
The ketone acting as lewis base ,reacts with alaminum chloride (Lewis acid) to form a complex
Step 6
Treating the complex with water liberates the ketone and hydrolyzes the Lewis acid

32. Preparation of nitrobenzene
By nitration of benzene in pesent of sulphoric acid replace hydrogen atom by (NO2) groups
nitrobenzene
benzene

33. Preparation of nitrobenzene
Nitrations are usually carried out at comparatively low temperatures
At high temp may loss of material b/c of oxidaising action of nitric acid

34. Preparation of nitrobenzene
Suphoric acid furnish astrong acid. medium to convert nitric acid into highly reactive nitronium ion NO2+

35. Procedure:
Add 9ml of nitric acid and add, in portion,with shaking conc. Sulphuric acid(10ml) to round-bottemed flask
Place the mixture in cold water and keep the temp between 50◦-55◦ use thermometer
Add slowly (1-2ml) pure benzene 7ml shake after each addition
When addition is complete warm the flask in water bath 60° for min with continued shaking.

37. Thank you