CBSE Class 10 Science 2020 · Paper 31/C/2 · Question 25(a)

(a) (i) Alcohol: butanol (butan-1-ol), ${\text{C}}_4{\text{H}}_9\text{OH}$, with the structure ${\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_2-{\text{CH}}_2-\text{OH}$. (ii) Aldehyde: butanal, ${\text{C}}_3{\text{H}}_7\text{CHO}$, with the structure ${\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_2-\text{CHO}$, the end carbon being double-bonded to oxygen and bonded to one hydrogen. The full structural formulas are drawn in the figure. (b) (1) Saturated hydrocarbons have only single bonds between carbon atoms (general formula ${\text{C}}_n{\text{H}}_{2n+2}$); unsaturated hydrocarbons have at least one double or triple bond between carbon atoms (${\text{C}}_n{\text{H}}_{2n}$ or ${\text{C}}_n{\text{H}}_{2n-2}$). (2) Saturated hydrocarbons are less reactive and undergo substitution reactions; unsaturated hydrocarbons are more reactive and undergo addition reactions. They also differ in how they burn: saturated hydrocarbons generally give a clean flame, unsaturated ones a yellow, sooty flame.