Question

The general formula of a group of organic compounds is ${C_n}{H_{2n + 1}}OH$.Write the molecular formula of the first two members of this group. Examine whether these two compounds are in homologous series based on their molecular.

Answer 1

Hint: A series of compounds have similar chemical properties and functional groups and the difference betters two successive members of the two series is by $C{H_2}$. And mass difference if of 14g, such series is known as homologous series. ${C_n}{H_{2n + 1}}OH$ is the general formula of alcohols attached with alkanes.

Complete step by step answer:
The general formula of alkanes is ${C_n}{H_{2n + 2}}$ for example methane and ethane have formula $C{H_3}$ and ${C_2}{H_6}$ respectively.
When an alcohol functional group is present with alkane, one hydrogen is removed or substituted with one alcohol $\left( { - OH} \right)$ group. The nomenclature of such compounds is done by changing the lending if parent alkane name with -OL.
The first two members of a homologous series with chemical formula ${C_n}{H_{2n + 1}}OH$will be having one and two carbons respectively. Therefore, the first two members are:-
1.$C{H_3}OH$(methanol),and
2.${C_2}{H_5}OH$(ethanol)
The difference between these two comp-rounds is that $C{H_2}$ is one carbon and two hydrogen atoms. Also the difference by mass is Hg hence these two comp wads are members of a same homologous series it alkane series.
Some more members of this series would be ${C_3}{H_7}OH$ (propanol), ${C_4}{H_9}OH$ (bioethanol), ${C_5}{H_{11}}OH$ (pentanes) and so on.


Note:
Like alkane there are many more homologous such as alkene series alkyne series etc. these series hone the same functional group. Biopolymers such as polymers of glucose are cellulose also form a homologous series as it is made up of repetitive units of glucose. The chemical and physical properties remain the same with an increase in molecular weight.