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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 ?

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Short Answer Type

144.

The $straight pi$ -bond is weaker than carbon-carbon σ bond. Explain.

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145.

Why are alkenes more reactive than alkanes ?

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Long Answer Type

146.

Why do alkenes undergo electrophilic addition reactions?

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147.

Discuss the mechanism of addition of bromine to ethylene.

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148.

Discuss the mechanism of addition hydrogen acids to symmetrical alkenes. Justify the order of reactivity of halogen acids HI > HBr > HCl.

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149.
Define Markownikoff's rule giving an example.

This rule states: In a normal addition, the negative part of the addendum (molecule to be added) adding to the double bond of an unsymmetrical alkene goes to that carbon atom which has lesser number of hydrogen atoms. Examples are: