Question

Consider the following compounds. Arrange these compounds in a n increasing order of reactivity with nitrating mixture. The correct order is : 

• A. $c<b<a$
• B. $b<c<a$
• C. $b<a<c$
• D. $c<a<b$

Hint:

For phenol derivatives, Nitro groups (EWG) at ortho/para positions significantly increase acidity due to resonance stabilization of the negative charge.

Answer 1

The Correct Option is A

To determine the increasing order of reactivity of the given compounds with nitrating mixture, we need to consider the effects of substituents on the aromatic ring with respect to electrophilic aromatic substitution (EAS).

Step-by-Step Explanation:

1. Identify the Substituents:
   • Compound (a) has a \(-\text{Cl}\) group.
   • Compound (b) has a \(-\text{NO}_2\) group.
   • Compound (c) has a \(-\text{OCH}_3\) group.
2. Effect on Reactivity:
   • \(-\text{Cl}\) is an electron-withdrawing group that deactivates the ring but directs electrophiles to ortho/para positions.
   • \(-\text{NO}_2\) is a strong electron-withdrawing group and deactivates the ring significantly, making it less reactive towards EAS.
   • \(-\text{OCH}_3\) is an electron-donating group that activates the ring and increases reactivity towards EAS.
3. Reactivity Order:

Considering the effects, the order of increasing reactivity with the nitrating mixture is:

\(c < b < a\)

Conclusion:

Based on the activating and deactivating effects of substituents, the correct order of reactivity of these compounds with a nitrating mixture is \(c < b < a\), as compound (c) with \(-\text{OCH}_3\) is least reactive, and compound (a) with \(-\text{Cl}\) is most reactive among the given options.