Question

What is the correct IUPAC name of

• A. 3-Bromo-2-hydroxy-5-nitrobenzoic acid
• B. 3-Bromo-4-hydroxy-1-nitrobenzoic acid
• C. 2-Hydroxy-3-bromo-5-nitrobenzoic acid
• D. 5-Nitro-3-bromo-2-hydroxybenzoic acid

Hint:

When naming substituted benzoic acids, the -COOH group is always at position 1. Number the benzene ring to give the lowest possible numbers to the other substituents based on their priority (functional groups>halogens>nitro groups). Finally, list the substituents alphabetically with their corresponding position numbers before the parent name "benzoic acid".

Answer 1

The Correct Option is A

The given compound is a substituted benzoic acid. To determine its IUPAC name, let's analyze the structure:

1. The main functional group is the carboxylic acid (\(\text{CO}_{2}\text{H}\)), and it is located on the benzene ring. This makes the compound a benzoic acid derivative.
2. The numbering of the benzene ring starts from the carbon attached to the carboxylic acid group (\(\text{CO}_{2}\text{H}\)). This is position 1.
3. Identify and number the substituents on the benzene ring:
   • \(\text{OH}\) (hydroxy group) is on position 2.
   • \(\text{Br}\) (bromo group) is on position 3.
   • \(\text{NO}_{2}\) (nitro group) is on position 5.
4. Following IUPAC nomenclature, the substituents are listed in alphabetical order: Bromo, Hydroxy, Nitro.
5. Thus, the correct IUPAC name is 3-Bromo-2-hydroxy-5-nitrobenzoic acid.

Justification:

• Options Explanation:
  • 3-Bromo-2-hydroxy-5-nitrobenzoic acid: This matches our analysis.
  • 3-Bromo-4-hydroxy-1-nitrobenzoic acid: Incorrect because the hydroxy group is at position 2, not 4.
  • 2-Hydroxy-3-bromo-5-nitrobenzoic acid: Incorrect sequence according to alphabetical order for naming.
  • 5-Nitro-3-bromo-2-hydroxybenzoic acid: Incorrect sequence according to alphabetical order for naming.

Therefore, the correct answer is 3-Bromo-2-hydroxy-5-nitrobenzoic acid.

Answer 2

To determine the correct IUPAC name, we need to follow the IUPAC nomenclature rules for substituted benzoic acids. 

1. Identify the parent compound: The parent compound is benzoic acid, as it contains a benzene ring with a -COOH group. The -COOH group is assigned position 1. 

2. Number the benzene ring: The numbering of the ring is done such that the substituent with the next priority gets the lowest possible number. The priority order for the substituents present is: -COOH (highest priority, assigned position 1)>-OH>-Br>-NO\( _2 \). Therefore, the -OH group should get the lowest possible number. Numbering clockwise gives -OH at position 2, -Br at position 3, and -NO\( _2 \) at position 5. Numbering counterclockwise would give -OH at position 6, which is higher. Thus, the clockwise numbering is correct. 

3. Identify the substituents and their positions: - -Br (bromo) is at position 3. - -OH (hydroxy) is at position 2. - -NO\( _2 \) (nitro) is at position 5.

4. Arrange the substituents alphabetically: The alphabetical order of the prefixes is bromo, hydroxy, nitro. 

5. Write the IUPAC name: Combining the position numbers and the alphabetically ordered prefixes with the parent name benzoic acid, we get: 3-bromo-2-hydroxy-5-nitrobenzoic acid. This matches option (1).