Question

Arrange the following in decreasing acidicstrength

• A. A > B > C > D
• B. B > A > C > D
• C. D > C > A > B
• D. D > C > B > A

Answer 1

The Correct Option is A

To determine the correct order of acidic strength, we need to analyze the structural features of each compound and understand the role of substituents on the benzene ring.

The acidic strength of a compound is influenced by the ability of the substituents to stabilize the conjugate base formed after the loss of a proton. Electron-withdrawing groups (EWG) tend to increase acidity as they stabilize the negative charge on the conjugate base through resonance or inductive effects, while electron-donating groups (EDG) decrease acidity.

1. Compound A: Contains a nitro group (\(\mathrm{-NO_2}\)) which is a strong electron-withdrawing group. This increases the acidic strength by stabilizing the conjugate base effectively.
2. Compound B: Contains a nitro group closer to the carboxylic acid, still a strong electron-withdrawing group but potentially slightly less impactful due to position relative to Compound A.
3. Compound C: Contains a methoxy group (\(\mathrm{-OCH_3}\)) which is an electron-donating group. This decreases the acidic strength as it destabilizes the conjugate base.
4. Compound D: Also contains a methoxy group but in a different position, hence similar reasoning applies as in Compound C.

The order of acidity based on the above reasoning is:

A > B > C > D 

This order aligns with the correct option provided, A > B > C > D. Thus, the presence and effects of electron-withdrawing and electron-donating groups have a critical influence on the acidic strength of aromatic compounds.