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Dehydrohalogenation for Alkenes

Which of the ...

Question

Which of the following compound(s) will not undergo $β$ - Elimination reaction on reacting with alcoholic KOH?

A

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B

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C

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D

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Solution

The correct options are
A
D
When an alkyl halide is treated with alcoholic KOH ( KOH dissolved in alcohol) it undergoes dehydrohalogenation to give alkene as product.
Removal of the halogen atom together with a hydrogen atom from a carbon adjacent to the one bearing the halogen. Since hydrogen is eliminated from the $β$ carbon atom, the dehydrohalogenation of alkyl halide is also known as β-Elimination reaction.
So for this particular reaction to proceed there should be a $β$ -hydrogen in the molecule.
In compound (a) and (d), there is no $β$ -hydrogen so they don't undergo elimination reaction in presence of alcoholic KOH.
Compound (b) has 2 $β$ -Hydrogen and compound (c) has 1 $β$ -Hydrogen so they undergo $β$ Elimination.

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Dehydrohalogenation for Alkenes

Standard XII Chemistry

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