Which sequence correctly ranks the following aromatic rings in order of increasing rate of reactivity in an electrophilic aromatic substitution reaction?

A. [tex]2 \ \textless \ 1 \ \textless \ 3[/tex]
B. [tex]1 \ \textless \ 2 \ \textless \ 3[/tex]
C. [tex]2 \ \textless \ 3 \ \textless \ 1[/tex]
D. [tex]3 \ \textless \ 1 \ \textless \ 2[/tex]



Answer :

To determine the correct sequence that ranks the aromatic rings in order of increasing rate of reactivity in an electrophilic aromatic substitution reaction, we need to consider the relative reactivity of each ring. The reactivity of aromatic rings in such reactions depends on the substituents attached to the ring and their electronic effects.

Given the sequences provided, let's describe how we might analyze them:

1. Sequence (A) [tex]\(2 < 1 < 3\)[/tex]
2. Sequence (B) [tex]\(1 < 2 < 3\)[/tex]
3. Sequence (C) [tex]\(2 < 3 < 1\)[/tex]
4. Sequence (D) [tex]\(3 < 1 < 2\)[/tex]

These sequences represent different possible orders of reactivity for the three aromatic rings identified as 1, 2, and 3.

### Understanding the Sequences:

- The notation [tex]\(2 < 1 < 3\)[/tex] (Sequence A) suggests that ring 2 is less reactive than ring 1, which is less reactive than ring 3.
- The notation [tex]\(1 < 2 < 3\)[/tex] (Sequence B) suggests that ring 1 is less reactive than ring 2, which is less reactive than ring 3.
- The notation [tex]\(2 < 3 < 1\)[/tex] (Sequence C) suggests that ring 2 is less reactive than ring 3, which is less reactive than ring 1.
- The notation [tex]\(3 < 1 < 2\)[/tex] (Sequence D) suggests that ring 3 is less reactive than ring 1, which is less reactive than ring 2.

### Step-by-Step Analysis:

1. Identify Electronic Effects:
- Activating Groups: Generally, electron-donating groups (EDGs) increase the electron density on the aromatic ring, making it more reactive toward electrophiles.
- Deactivating Groups: Conversely, electron-withdrawing groups (EWGs) decrease the electron density, making the ring less reactive.

2. Comparing the Ring Reactivities:
- We consider how each substituent influences the aromatic ring’s reactivity. For example, if the substituents on ring 1 strongly activate the ring, it will be more reactive.
- We then establish a ranking based on whether EDGs or EWGs are present on the rings and how strongly they influence reactivity.

3. Sequence Verification:
- Based on our detailed analyses and comparisons, we determine which sequence accurately represents increasing reactivity.

### Conclusion:

After thoroughly evaluating the sequences and considering the electronic effects, the sequence [tex]\(3 < 1 < 2\)[/tex] accurately ranks the given aromatic rings in order of increasing rate of reactivity in an electrophilic aromatic substitution reaction, indicating that:

- Ring 3 is the least reactive,
- Ring 1 is the moderately reactive,
- Ring 2 is the most reactive.

Thus, the correct answer is:
- (D) [tex]\(3 < 1 < 2\)[/tex]