friedel craft reaction-4.ppt (1)
TRANSCRIPT
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Friedel-CraftRaction
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Dr. M. Abbas BhattiPh.D (Scholar-BZU), M.Phil (PU),B.Phar (PU)
Pharmaceutical Chemistry
Islam College of Pharmacy, Sialkot.
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S!bstit!tion
"lectro#hilic S!bstit!tion reaction(aroatic s$ste)%
The reaction in which
hydrogenof Benzene aromatic system! isre"laced#y an electro"hile"ositi$ely charged
electron lo$ing grou"! are calledelectro"hilic
su#ustitution reaction.
%%& "age
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&earnin' obecties
(hat is )riedel*craft reaction and its "rinci"les
+efinition of ewis acid-
Ty"e of )riedel*craft reactions- Significance and "harmaceutial a""lications of
)riedel*craft reactions.
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Friedel-Crafts Reaction
n alkyl grou"can #e introducedinto an
aromatic ring#y a reaction known as )riedel*
Crafts reaction.
In this reaction an aromatic com"oundis
treated with an alkyl or acylhalides in the
"resence of a ewis acidlCl', )eCl'/other
metal halides! 0 su#stitutedaromaticcom"ound is formed.
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lCl'
These are further di$idedinto
I. )riedel*Crafts lkylation. II. )riedel*Crafts cylation.
*. Friedel-Crafts Al+$lation%
The reaction of an alkyl halidewith#enzenein
the "resence of ewis acid catalyst lCl'! is
called 3
4 C5'Cl 4 5CllCl'
C5'
Benzene Toluene
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%
Mechanis. )ollowing ste"s are in$ol$ed
Ste# .)ormation of the electro"hile C5'!.
C5'6 Cl 4 lCl' C5' 4 lCl&
Ste# .The electro"hile attacks the #enzenering to gi$e a car#onium ion.
4 C5'
/
5
C5'
Benzene Car#onium ion
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5
Ste# 0.oss of "roton gi$es alkyl#enzene.
4 5Cl 4 lCl'
5
C5'
C5'
lCl&
4
8
Toluene
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A##lications%
)riedel*Crafts alkylation is the most usefulmethodfor the synthesisof alkyl #enzenes0mi:ed ketones.
Dra1bac+s of Friedel-Crafts al+$lation% a.It is difficult to sto"the reaction when one
alkyl grou"has entered the ring, di 0 trialkyl#enzenes are also form.
b.The alkyl grou"often tends to rearrange. e.g., (hen #enzene is treated with n*"ro"yl
chloride, the "roduct is iso"ro"yl#enzenerather than the e:"ected n*"ro"yl#enzene.
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**. Friedel-Crafts Ac$lation
The reaction of an acyl halidewith #enzene in
the"resenceof ewis acid lCl'! is called 3
Ste# .The electro"hile attacks the #enzene
ring to form a car#onium ion.
4
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Ste# 0.oss of "roton gi$es an aromatic
ketone.
Adanta'es%
a.?o Polyacylated "roducts are formed. b.?o rearrangement "roducts are formed.
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A##lications%
a.romatic ketonescan #e "re"ared.
b.n*"ro"yle #enzenecan #e "re"ared which is
a @Clemenson Aeduction.
CH2CH2CH3
Benzenen*
Pro"yl#enzene
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2ther *nd!strial A##lications
Toluene is a common sol$ent, e.g. for"aints,
"aint thinners, silicone sealants, many chemical
reactants, ru##er,"rinting ink, adhesi$esglues!,
lacuers, leather tanners, and disinfectants.
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References
A TEXT BOOK OF ORGANIC CHEMISTRY
BY B.S. Bahl.
A TEXT BOOK OF ORGANIC CHEMISTRY
BY M. YOUNAS.
&e1is acid% s!bstance forin' coalent bond% a su#stance that can acce"t a "air of
electrons from a #ase to form a co$alent #ond.
Carboni! ion% or'anic ion% that has a car#on atom #earing a "ositi$e charge.
Aceto#henone% colorless li3!id cheical% with a sweet "ungent smell and taste. Dse
"erfumes, sol$ent, fla$oring.