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AROMATICcompounds

Made by: AYESHA AFTAB MALIKBs in bioinformatics

International Islamic university Islamabad Pakistan

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.

History of aromatic compounds: August Wilhelm Hofmann

in 1855

August Kekulé in 1865

J. J. Thomson, between 1897 and 1906

Sir Robert Robinson, in 1925

Ernest Crocker in 1922

Hückel in 1931.

Physical properties of benzene

Benzene is a colorless, mobile and volatile liquid

It's boiling point is 80°C and freezing point is 5.5°C.

It has characteristic odor

 It is highly inflammable and burns with sooty flame

It is lighter than water. It's specific gravity at 20°C is 0.8788

immiscible with water miscible with organic solvents such as alcohol and ether.

Benzene itself is a good solvent

It is a non-polar compound and its dipole moment is zero.

It is an extremely poisonous substance

Chemical properties of benzene

Bromination.Addition of bromine to benzene

.Ferric bromide or aluminum chlorite as a catalyst

Hydrogenation of benzene.Addition of hydrogen in

benzene .Ni as a catalyst

.300 c temp. and 30atm pressure

Nitration of Benzene.introduction of nitro group

.nitric or sulphuric acid as a catalyst

Chlorination of benzene.Addition of chlorine

.sunlight as a catalyst

Sulphonation of benzene.introduction of sulphonic

acid group

Friedal craft reaction

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

Alkyl group

any group derived from an alkane by the removal of one hydrogen atom. Alkyl groups are often designated by the symbol R.

General reactionwhere R= any alkyl group

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

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-

Friedal craft acylation

What is polycyclic aromatic hydrocarbon?

They consist of three or more benzene rings

commonly produced by fossil fuel combustion.

Also called polynuclear aromatic hydrocarbon.

Uses of Benzene

Tire/Rubber Manufacturing

Petroleum/Oil/Asphalt

Chemicals/Plastic

Auto Repair

Printing/Painting

Health hazards

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