What is IUPAC name of following compound? Choose the correct answer from the options given below.
Show Hint
Isolate the principal group first to find the parent name. Since $-\mathrm{COOH}$ takes absolute priority, the compound must end with "benzoic acid". This immediately eliminates options (A) and (B), leaving a simple choice based on counting positions.
Step 1: Understanding the Question:
The problem presents a trisubstituted benzene ring featuring a methyl group ($-\mathrm{CH}_3$), a carboxyl group ($-\mathrm{COOH}$), and an aldehyde group ($-\mathrm{CHO}$). We need to identify the correct IUPAC nomenclature according to standard priority assignment rules. Step 2: Key Formula or Approach:
According to IUPAC rules for polyfunctional compounds, the principal functional group is chosen based on a strict seniority hierarchy:
$$\text{Carboxylic acid } (-\mathrm{COOH}) > \text{Aldehyde } (-\mathrm{CHO}) > \text{Alkyl group } (-\mathrm{R})$$
The principal group defines the parent name (benzoic acid) and sets position C1 on the ring. The remaining groups are treated as secondary prefixes arranged in alphabetical order. Step 3: Detailed Explanation:
1. The principal group is the carboxylic acid ($-\mathrm{COOH}$), so the parent ring is benzoic acid, assigning the carbon holding it as position 1.
2. Number the ring towards the closest substituent to respect the lowest locant rule. The positions become:
Carboxyl group at position 1.
Formyl prefix ($-\mathrm{CHO}$) at position 3.
Methyl prefix ($-\mathrm{CH}_3$) at position 6.
3. Alphabetize the substituent prefixes: "Formyl" precedes "Methyl". Combining these positions with the parent name yields: 3-Formyl-6-methyl benzoic acid. Step 4: Final Answer:
The correct IUPAC name is 3-Formyl-6-methyl benzoic acid, corresponding to option (C).
