Question

The formation of 1, 2 dibromoethane from ethene and bromine is an example of:
(A) Substitution reaction
(B) Dehydration reaction
(C) Dehydrohalogenation reaction
(D) Addition reaction

Answer 1

Hint: Ethene has a double bond between two carbon atoms. For the formation of 1, 2 dibromoethane, this carbon-carbon double bond is broken as 1, 2 dibromoethane becomes saturated compound whereas ethene is an unsaturated compound.

Complete Step by Step Solution:
The reaction in which the addition of other atoms takes place, by replacing a double bond or a triple bond is known as addition reaction.
Ethene has a C=C double bond. When bromine reacts with ethene, one of the double bonds is broken, and one atom of bromine is attached to each carbon atom by a single bond.
Thus, the addition of bromine to ethene is termed as an additional reaction.
${{H}_{2}}C=C{{H}_{2}}+B{{r}_{2}}\to {{H}_{2}}BrC-CBr{{H}_{2}}$
The reaction, in which one functional group of an atom is replaced or displaced by another functional group in the same atom, is known as Substitution reaction or Displacement reaction.
In this reaction substitution does not take place. Thus, it is not a Substitution reaction.
The reaction which involves the removal of hydrogen atom from the given compound is known as dehydration reaction.
Ethene does not lose any of its hydrogen atom in the process of formation of 1,2 dibromoethane. Thus, the reaction is not a dehydration reaction.
The reaction in which the compound loses its hydrogen and halogen atom to give another product is known as Dehydrohalogenation reaction.
In the given reaction, the reactant doesn’t have any halogen atom in it. Thus, it cannot lose any halogen atoms. Hence, the reaction is not a Dehydrohalogenation reaction.

Hence, (D) is the correct option.

Note: A different compound shows different reactions. An Additional reaction has some rule that should be followed like it is always associated with unsaturated compounds to form saturated compounds. Secondly in this reaction there is no elimination or removal of any molecule.