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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:

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

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143.
How are alkenes prepared from Alkynes ?

Alkenes are prepared by the partial reduction of alkynes.

(a) Using Lindlar’s catalyst. Catalytic reduction of alkynes in the presence of palladium catalyst deposited over BaSO₄ or CaSO₄ and partially poisoned by S or quinoline (Lindlar’s catalyst) predominantly gives us alkenes.

(b) Using Birch reduction. If alkynes are reduced by sodium and liquid ammonia (Birch reduction), trans-alkenes are major products.