Which of the following hydrocarbons undergo addition reactions: ${\mathrm{C}}_2{\mathrm{H}}_6,{\mathrm{C}}_3{\mathrm{H}}_8,{\mathrm{C}}_3{\mathrm{H}}_6,{\mathrm{C}}_2{\mathrm{H}}_2$ and ${\mathrm{CH}}_4$?

Addition reaction

• When two or more reactants combine to create one product, it is called an addition reaction.
• Unsaturated compounds can undergo addition reactions.
• Addition reaction is mainly four type: Electrophilic addition, Nucleophilic addition, Free-radical addition and Cycloaddition.
• An addition reaction involving a reactant with numerous bonds, such as a double or triple bond, is known as an electrophilic addition reaction.
• A chemical molecule having an electron-deficient or electrophilic double or triple bond participates in a nucleophilic addition reaction.
• Free-radical addition is a kind of addition reaction used in organic chemistry.
• A cycloaddition is a chemical process that combines two or more unsaturated molecules to create a cyclic adduct with a net decrease in the number of bonds.

${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{6}}$

• ${\mathrm{C}}_2{\mathrm{H}}_6$ is the molecular formula of ethane.
• Ethane is a saturated hydrocarbon.
• Structure of ${\mathrm{C}}_2{\mathrm{H}}_6$:

${\mathbf{C}}_{\mathbf{3}}{\mathbf{H}}_{\mathbf{8}}$

• ${\mathrm{C}}_3{\mathrm{H}}_8$ is the molecular formula of propane.
• Propane is a saturated hydrocarbon.
• Structure of ${\mathrm{C}}_3{\mathrm{H}}_8$:

${\mathbf{C}}_{\mathbf{3}}{\mathbf{H}}_{\mathbf{6}}$

• ${\mathrm{C}}_3{\mathrm{H}}_6$ is the molecular formula of propene.
• Propene is unsaturated hydrocarbon having one double bond.
• Structure of ${\mathrm{C}}_3{\mathrm{H}}_6$:

${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{2}}$

• ${\mathrm{C}}_2{\mathrm{H}}_2$ is the molecular formula of ethyne.
• Ethyne is unsaturated hydrocarbon having one triple bond.
• Structure of ${\mathrm{C}}_2{\mathrm{H}}_2$:

${\mathbf{CH}}_{\mathbf{4}}$

• ${\mathrm{CH}}_4$ is the molecular formula of methane.
• Methane is a saturated hydrocarbon.
• Structure of ${\mathrm{CH}}_4$:

• Only unsaturated compound can undergo addition reaction.
• ${\mathrm{C}}_3{\mathrm{H}}_6$ and ${\mathrm{C}}_2{\mathrm{H}}_2$ are the only unsaturated hydrocarbons among the given hydrocarbons.
• Therefore, only ${\mathrm{C}}_3{\mathrm{H}}_6$ and ${\mathrm{C}}_2{\mathrm{H}}_2$ undergo addition reaction.