Dihalogen Compounds
Dihalogen Compounds

Chemical reactions:
Vic. dihalide:
1- Dehydrohalogenation:
CH3 – CH2 alc. KOH,-HCl CH2 = CHClalc. KOH,-HCl
Cl
Cl
CH≡CH
B)
Dihalogen Compounds

Chemical reactions:
Vic. dihalide:
2- Dehalogenation:
B)
Dihalogen Compounds

Chemical reactions:
Vic. dihalide:
3- Effect of aqueous KOH:
B)
Dihalogen Compounds

Chemical reactions:
C) α. ω. dihalide:
Trihalogen Compounds
Trihalogen Compounds

Preparation:
- It is prepared by the action of bleaching powder (as a source of
chlorine), on ethyl alcohol or acetone. The reaction is known as
Chloroform reaction.
Trihalogen Compounds

Preparation:
2- From acetone:
Trihalogen Compounds

Preparation:
3- By the partial reduction of carbon tetrachloride with
iron filings and water.
-
When prepared by this way, chloroform is used for
solvent purposes and not for anesthesia.
Trihalogen Compounds

Chemical reactions:
1- Hydrolysis with boiling alkalies, gives formic acid.
Trihalogen Compounds

Chemical reactions:
2- Reduction with hydrogen or zinc and water gives
methane
Trihalogen Compounds

Chemical reactions:
-
Chloroform decomposes with moist air to give
phosgene or carbonyl chloride, which is a
poisonous gas.
Trihalogen Compounds

Chemical reactions:
-
For that reason chloroform is stored in brown
bottles which must be completely filled (to
minimize contact with air) and to which is
added 1-2% ethyl alcohol which reacts with
any formed phosgene to form ethyl
carbonate which is harmless.
Trihalogen Compounds
Chemical
reactions:
Polyhalogen Compound

-
-
Carbon tetrachloride CCl4 (pyrene)
It is a colorless liquid B.P. 77°C
Immiscible and heavier than water
The vapors of CCl4 are non-inflammable.
It is used in fire-extinguishers under the
name of pyrene.
Polyhalogen Compound

-
Preparation:
It is prepared industrially by the action of chlorine on
carbon disulphide in the presence of aluminum chloride
as catalyst.
Polyhalogen Compound

Dichloro difluoro methane CCl2F2 (Freon)
-
It is used as refrigerant under the name of Freon.
-
Preparation:
Polyhalogen Compound

-
Acetylene tetra chloride (tetrachloroethane) CHCl2
– CHCl2
It is a very toxic, a colurless liquid B.P. 146, noninflammable, it is used as a solvent for oil, fats, Paints,
varnishes and rubber.
Polyhalogen Compound

Tetrafluoroethylene C2F4 (gas)
- By the action of antimony trifluoride and hydrogen fluorid on
chloroform, and then heating the chlorodifluoromethane so
produced at 800°C.
Polyhalogen Compound



When tetrafluoroethylene is polymerized, the plastic
Teflon is produced
Which is inert to most chemicals even to boiling with
conc. acids.
Teflon is insoluble in most organic solvents so it is
fabricated into pipes, gaskets and other equipments
used in chemical factors.
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