Question

(a) Give the names and structural formulae of the next two higher homologues of methane.
(b) The molecular formula of a hydrocarbon is $C_{10}{H}_{18}.$ Name its homologous series.
(c) Select the hydrocarbons which are members of the same homologous series. Give the name of each series.
$C_5{H}_{10};C_3{H}_8;C_6{H}_{10};C_4{H}_{10};C_7{H}_{12};C_8{H}_{16}$

Answer 1

(a) Ethane $\left(C_2{H}_6\right)$ and propane $\left(C_3{H}_8\right)$ are the names of the successive homologues of methane.
Their structural formulae are as follows:


(b) The homologous series of a hydrocarbon with the molecular formula $C_{10}{H}_{18}$ is alkynes $Cn{H}_{2n-2}$.

(c)
(i) $C_3{H}_8$ and​ $C_4{H}_{10}$ are the hydrocarbons belonging to the homologous series of alkanes.
(ii) $C_5{H}_{10}$ and​ $C_8{H}_{16}$ are the hydrocarbons belonging to the homologous series of alkenes.
(iii) $C_6{H}_{10}$ and​ $C_7{H}_{12}$ are the hydrocarbons belonging to the homologous series of alkynes.