Dihalogen Compounds. Chemical reactions: B) Vic. dihalide: 1- Dehydrohalogenation: CH 3 – CH 2 alc. KOH,-HCl CH 2 = CHCl alc. KOH,-HCl Cl Cl CH≡CH.

Dihalogen Compounds

Dihalogen Compounds

Chemical reactions:

B) Vic. dihalide:

1- Dehydrohalogenation:

CH3 – CH2 alc. KOH,-HCl CH2 = CHClalc. KOH,-HCl

Cl Cl

CH≡CH

Dihalogen Compounds

Chemical reactions:

B) Vic. dihalide:

2- Dehalogenation:

Dihalogen Compounds

Chemical reactions:

B) Vic. dihalide:

3- Effect of aqueous KOH:

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, non-inflammable, 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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