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Hydrocarbons

Short Answer Type

141.

What happens when:

(i) Ethyl alcohol is heated in the presence of Al₂O₃ at 493 K?

(ii) Ethylene dibromide is heated with zinc dust?

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Long Answer Type

142.
Explain the mechanism of the following reaction:

$straight C subscript 2 straight H subscript 5 OH space rightwards arrow from 440 space straight K to Conc. space straight H subscript 2 SO subscript 4 of space CH subscript 2 space equals space CH subscript 2 space plus space straight H subscript 2 straight O$

Mechanism of the above reaction involves three steps:

(i) Formation of protonated alcohol. H₂SO₄ionises to give H⁺ ion which attacks the molecule of alcohol to form protonated alcohol.

(ii) Formation of the carbocation. Protonated alcohol eliminates a molecule of water to give a carbocation.

(iii) Formation of ethylene. Carbocation finally loses a proton to hydrogen sulphate ion to form ethylene.