Question

The molecular formula of two carbon compounds are C₄H₈ and C₃H₈. Which one of the two is most likely to show addition reaction? Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case. 

Answer 1

Compound X has the molecular formula = C₄H₈ (C_nH_2n, alkene)
Compound Y has the molecular formula = C₃H₈ ( C_nH_2n+2, alkane)
C₄H₈ is unsaturated hydrocarbon, i.e. alkene (butene) and C₃H₈ is a saturated hydrocarbon, i.e. alkane (propane).
Saturated compounds undergo substitution reaction.
Unsaturated compounds undergo addition reaction at the multiple bonds. For example, 1-butene and 2-butene will add a chlorine molecule (Cl₂) to form 1,2-dichlorobutane and 2,3-dichlorobutane, respectively. The reaction will be:

CH₃CH₂CH=CH₂ + Cl₂ → CH₃CH₂CH(Cl)−CH₂Cl
Or
CH₃CH=CHCH₃ + Cl₂ → CH₃CH(Cl)−CH(Cl)CH₃