CBSE Class 10 Science 2017 · Paper 531 · Question 19

Differences between saturated and unsaturated hydrocarbons: (1) Bonding: in a saturated hydrocarbon the carbon atoms are joined by single bonds only; an unsaturated hydrocarbon has at least one double or triple bond between carbon atoms. (2) Reactivity: saturated hydrocarbons are fairly unreactive and undergo substitution reactions (for example with chlorine in sunlight); unsaturated hydrocarbons are more reactive and undergo addition reactions (for example with hydrogen in the presence of a nickel or palladium catalyst). Examples: saturated, ethane (${\text{C}}_2{\text{H}}_6$); unsaturated, ethene (${\text{C}}_2{\text{H}}_4$). General formula of the alkyne series: ${\text{C}}_n{\text{H}}_{2n-2}$. Second member: propyne, ${\text{C}}_3{\text{H}}_4$, with the structure $\text{H}-\text{C}\equiv \text{C}-{\text{CH}}_3$, in which the last carbon carries three hydrogen atoms (drawn in full in the figure).