Question

Homologue of $HCHO$ is:

• A. ${CH}_{2}O$
• B. ${CH}_{4}O$
• C. ${C_{2}H}_{2}O$
• D. ${C_{2}H}_{4}O$

Answer 1

The correct option is D ${C_{2}H}_{4}O$

A homologous series is a series of compounds with the same general formula, usually varying by a single parameter such as the length of a carbon chain.

Examples of such series are the straight - chained alkanes (paraffins) and some of their derivatives (such as the primary alcohols, aldehydes and (mono) carboxylic acids) varying by $-C{H}_2$.

One molecule of $HCHO$ (formaldehyde) contains one carbon atom, two hydrogen atoms and one oxygen atom.

Its homologue will contain one $C{H}_2$ group extra.

Thus, one molecule of homologue of $HCHO$ (formaldehyde) will contain two carbon atoms, four hydrogen atoms and one oxygen atom.

Its formula is ${C_{2}H}_{4}O$ or $C{H}_{3}CHO$, which is acetaldehyde.

Option D is correct.