Question

What is the next homologue of ${C_3}{H_7}OH$ called?

Answer 1

The formula of any hydrocarbon contains the information about its structure and can be used to determine the homologues by adding one carbon atom to the chain. The functional group present in the compound can be used for its naming.

Complete answer:
The given organic compound with the formula ${C_3}{H_7}OH$ is the third member of the alkane family with a hydroxyl group attached to it. The subscripts indicate the number of atoms of a particular element present in one molecule. The formula ${C_3}{H_7}OH$ suggests that this compound contains three carbons atoms, covalently bonded to seven hydrogen atoms and one hydroxyl group.
The general formula for the homologous series containing alcohols can be written as follows:
${C_n}{H_{2n + 1}}OH$
Thus, the value of $n$ in ${C_3}{H_7}OH$ is three. The next homologue or the next member of this series would contain one additional carbon atom, the value of $n$ would be four and the number of hydrogens atoms would change accordingly. The hydroxyl group would remain intact and not change with the change in number of carbon atoms. Thus the formula for next homologue is:
${C_4}{H_9}OH$
The IUPAC name of the compound ${C_4}{H_9}OH$ will contain the prefix “butan” as there are four single bonded carbon atoms in the chain and the suffix “ol” due the presence of the alcohol functional group.
Hence, the next homologue is ${C_4}{H_9}OH$ and it is called butanol.

Note:
The formula of the hydrocarbon indicates the numbers of atoms and the functional groups present but the position of the functional group cannot be determined by the formula alone. The given alcohol could be a primary or a secondary alcohol.