Chemistry - Nomenclature Question with Solution | TestHub

The IUPAC priority order for functional groups is crucial for naming organic compounds. The general order is carboxylic acids, sulfonic acids, esters, acid halides, amides, nitriles, aldehydes, ketones, alcohols, phenols, thiols, amines, ethers, alkenes, alkynes, and alkanes.

For the given options, the correct decreasing order of priority is:

Carboxylic acid ($-\mathrm{COOH}$) > Sulfonic acid ($-{\mathrm{SO}}_3\mathrm{H}$) > Amide ($-{\mathrm{CONH}}_2$) > Aldehyde ($-\mathrm{CHO}$).

Therefore, option A is correct.