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 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

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 CCl 4 (pyrene) - It is a colorless liquid B.P. 77°C - Immiscible and heavier than water - The vapors of CCl 4 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 CCl 2 F 2 (Freon) - It is used as refrigerant under the name of Freon. - Preparation:

Polyhalogen Compound Acetylene tetra chloride (tetrachloroethane) CHCl 2 – CHCl 2 - 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 C 2 F 4 (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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