Question

In a reaction, if half of the double bond is broken and two new bonds are formed, this is a case of
A. Elimination
B. Addition
C. Displacement
D. Rearrangement

Answer 1

Hint: Addition reaction is a chemical reaction in which two or more reactants react to form an individual product. Elimination, displacement, or rearrangement reactions do not include the breaking of half of the double bonds and the formation of two new bonds.

Complete Step by Step Solution:
Here in this question, we have to find out a reaction in which half of the double bond is broken and two new bonds are formed.
A. Elimination
Elimination reaction involves the elimination of a couple of atoms or a group of atoms in the presence of a suitable reagent giving rise to unsaturated compounds.
These reactions are utilised to convert saturated compounds to unsaturated compounds.
So, these types of reactions do involve double bonds but lead to the formation of double bonds.
So, A is incorrect.
B. Addition
An addition reaction is a chemical reaction in which two or more reactants react to form an individual product.
Chemical compounds comprising multiple bond characters can undergo these types of reactions.
Double or triple bonds are usually broken down to create single bonds.
It is the opposite of an elimination reaction.
For example, the conversion of ethene to 1,2-dibromoethane.

The double bond is broken and two new bonds are formed.
So, B is correct.

C. Displacement
A displacement reaction or a single replacement reaction is a chemical reaction in which one element is displaced by another in a compound.
It can be depicted as:
\[A + BC \to AC{\rm{ }} + {\rm{ }}B\]
where
A and B are different metals and C is an anion.
Or
A, and B are halogens and C is a cation.

D. Rearrangement
A rearrangement reaction is a category of organic reactions involving the carbon skeleton of a molecule that is rearranged to provide a structural isomer of the actual molecule.
It mainly involves the moving of the substituent from one atom to another atom in one molecule.
So, these reactions are mainly intramolecular.
So, D is incorrect.
So, option B is correct.

Note: Addition reactions are restricted to chemical compounds that possess multiple bonds like molecules with carbon-carbon double bonds or alkenes or with triple bonds or alkynes and compounds that possess rings. Molecules comprising carbon—hetero double bonds, for example, carbonyl (\[{\rm{C = O}}\]) groups, or imine (\[{\rm{C = N}}\]) groups, can go through addition due to double-bond character.