Draw formulas for the first five members of each homologous series beginning with the following compounds.

Solution:

The first five members of each homologous series beginning with the given compounds are shown as follows:

(a)

H-COOH : Methanoic acid

$\mathrm{CH}_{3}-\mathrm{COOH}$ : Ethanoic acid

$\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{COOH}$ : Propanoic acid

$\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{COOH}:$ Butanoic acid

$\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{COOH}$ : Pentanoic acid

(b)

$\mathrm{CH}_{3} \mathrm{COCH}_{3}$ : Propanone

$\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{3}$ : Butanone

$\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}$ : Pentan-2-one

$\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}$ : Hexan-2-one

$\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}$ : Heptan-2-one

(c)

$\mathrm{H}-\mathrm{CH}=\mathrm{CH}_{2}$ : Ethene

$\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2}$ : Propene

$\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}: 1$-Butene

$\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}:$ 1-Pentene

$\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}=\mathrm{CH}_{2}: 1$-Hexene