MHTCET 11 May 2024 Shift 2 Paper

Concept:When both $-\mathrm{COOH}$ and $-\mathrm{OH}$ are present on a benzene ring, the carboxylic acid group is the principal functional group. So the parent is benzoic acid, not phenol.Explanation:The given compound has three groups on the benzene ring: $-\mathrm{COOH}$, $-\mathrm{OH}$, and $-\mathrm{C}_2\mathrm{H}_5$.Since $-\mathrm{COOH}$ has the highest priority, the parent is benzoic acid and the carboxyl carbon is numbered as position $1$.The other substituents occupy positions $3$ and $5$.According to IUPAC rules, substituents are cited in alphabetical order. Ethyl ($\mathrm{C}_2\mathrm{H}_5$) comes before hydroxy ($\mathrm{OH}$), so ethyl gets the lower locant $3$ and hydroxy gets locant $5$.Hence the correct IUPAC name is $3$-ethyl-$5$-hydroxybenzoic acid.Answer:$\text{3-ethyl-5-hydroxybenzoic acid}$Correct option: C.