benzene
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Transcript of benzene
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AROMATICcompounds
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Made by: AYESHA AFTAB MALIKBs in bioinformatics
International Islamic university Islamabad Pakistan
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Aromatic compounds:
a hydrocarbon with alternating double an single bonds between carbon atoms
containing one or more benzene rings that are characteristic of the benzene series of compounds.
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Benzene and Aromatic Compounds Benzene (C6H6) is the simplest aromatic
hydrocarbon (or arene). Benzene has four degrees of unsaturation,
making it a highly unsaturated hydrocarbon. Whereas unsaturated hydrocarbons such as
alkenes, alkynes and dienes readily undergo addition reactions, benzene does not.
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History of aromatic compounds: August Wilhelm Hofmann
in 1855
August Kekulé in 1865
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J. J. Thomson, between 1897 and 1906
Sir Robert Robinson, in 1925
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Ernest Crocker in 1922
Hückel in 1931.
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Physical properties of benzene
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Benzene is a colorless, mobile and volatile liquid
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It's boiling point is 80°C and freezing point is 5.5°C.
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It has characteristic odor
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It is highly inflammable and burns with sooty flame
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It is lighter than water. It's specific gravity at 20°C is 0.8788
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immiscible with water miscible with organic solvents such as alcohol and ether.
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Benzene itself is a good solvent
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It is a non-polar compound and its dipole moment is zero.
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It is an extremely poisonous substance
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Chemical properties of benzene
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Bromination.Addition of bromine to benzene
.Ferric bromide or aluminum chlorite as a catalyst
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Hydrogenation of benzene.Addition of hydrogen in
benzene .Ni as a catalyst
.300 c temp. and 30atm pressure
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Nitration of Benzene.introduction of nitro group
.nitric or sulphuric acid as a catalyst
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Chlorination of benzene.Addition of chlorine
.sunlight as a catalyst
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Sulphonation of benzene.introduction of sulphonic
acid group
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Friedal craft reaction
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Friedal craft alkylation
Friedel–Crafts alkylation involves the alkylation of an aromatic ring with an alkyl halide using a strong Lewis acid catalyst. With anhydrous ferric chloride as a catalyst, the alkyl group attaches at the former site of the chloride ion
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Alkyl group
any group derived from an alkane by the removal of one hydrogen atom. Alkyl groups are often designated by the symbol R.
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General reactionwhere R= any alkyl group
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Friedel craft Acylation
. Acylation means substituting an acyl group into something - in this case, into a benzene ring.
The most commonly used acyl group is CH3CO-. This is called the ethanoyl group
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Acyl group
An acyl group is an alkyl group attached to a carbon-oxygen double bond. If "R" represents any alkyl group, then an acyl group has the formula RCO-
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Friedal craft acylation
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What is polycyclic aromatic hydrocarbon?
They consist of three or more benzene rings
commonly produced by fossil fuel combustion.
Also called polynuclear aromatic hydrocarbon.
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Uses of Benzene
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Tire/Rubber Manufacturing
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Petroleum/Oil/Asphalt
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Chemicals/Plastic
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Auto Repair
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Printing/Painting
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Health hazards
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What Products Have High Levels of Benzene?
Cigarettes Styrofoam(use mostly in food
containers) Cumene (paint thinner, lacquer thinner,
brush cleaner, paint stripper and spray paint) Benzene in Soft Drinks
Gasoline
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