Question

The $^1$H-NMR spectral data of a compound X is as follows: $\delta$ (ppm): 11.6 (s, 1H, exchangeable with D$_2$O), 7.60 (d, 1H, $J = 7.2$ Hz), 7.20 (t, 1H, $J = 7.2$ Hz), 6.90 (d, 1H, $J = 7.2$ Hz), 3.70 (s, 3H), 3.58 (s, 3H)Based on the spectral data, choose the appropriate structure for compound X.

• A. A
• B. B
• C. C
• D. D

Hint:

In aromatic $^1$H-NMR, a d-t-d pattern usually indicates three adjacent aromatic protons in a 1,2,3-trisubstituted benzene ring

Answer 1

The Correct Option is B

Step 1: Read the exchangeable peak.
The singlet near 11.6 ppm that exchanges with D$_2$O points to a carboxylic acid proton.

Step 2: Read the methoxy peaks.
Two three proton singlets near 3.6 to 3.7 ppm show two different methoxy groups.

Step 3: Read the aromatic pattern.
A doublet, triplet and doublet for one proton each means three neighbouring aromatic hydrogens, so the ring is 1,2,3 substituted.

Step 4: Match the structure.
Only structure B carries one acid group and two different methoxy groups with three adjacent ring protons.

Step 5: Answer.
\[ \boxed{\text{B}} \]