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 Multiple Choice QuestionsShort 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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 Multiple Choice QuestionsLong 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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 Multiple Choice QuestionsShort Answer Type

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144.

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


The >C = C< bond is made of σ bond and  bond. The  bond is weaker than σ  bond because electron in the  bond are more diffused in space i.e. orbitals participating in the  bond formation overlap sidewise only to small extent. On the other hand, orbitals participating in the σ bond formation overlap axially to a greater extent.




The greater the extent of overlapping, the higher the probability of finding the valence electrons in between the nuclei and hence the bond will be stronger and shorter. Hence overlap in  bond is less effective as compared to σ bond.

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145.

Why are alkenes more reactive than alkanes ?

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 Multiple Choice QuestionsLong 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.

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150. Give the mechanism of Markownikoffs rule as applied to unsaturated hydrocarbons.
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