Question

Identify the ortho and para directing groups towards aromatic electrophilic substitution reactions from the following list.

• A. I, IV, V
• B. II, III, VI
• C. I, II, IV
• D. IV, V, VI

Hint:

Electron donating groups such as \(-OH\), \(-OR\), and \(-NHCOR\) are generally ortho and para directing, while strong electron withdrawing groups like \(-CN\), \(-CHO\), and \(-COOH\) are meta directing.

Answer 1

The Correct Option is A

Step 1: Understand ortho and para directing groups.
In aromatic electrophilic substitution reactions, substituents already present on the benzene ring decide the position of incoming electrophile.
Electron donating groups generally activate the benzene ring and direct the incoming electrophile to ortho and para positions.

Step 2: Identify electron donating groups.
The groups \(-OH\), \(-OCH_3\), and \(-NHCOCH_3\) donate electron density to the benzene ring through resonance.
Due to resonance donation, electron density increases mainly at ortho and para positions.
Therefore, these groups are ortho and para directing groups.

Step 3: Analyze the given groups.
\[ I = -OH \] \(-OH\) is an activating ortho and para directing group due to \(+R\) effect.
\[ IV = -OCH_3 \] \(-OCH_3\) is also an ortho and para directing group because oxygen donates lone pair electrons by resonance.
\[ V = -NHCOCH_3 \] \(-NHCOCH_3\) also donates electrons through resonance and directs electrophilic substitution to ortho and para positions.

Step 4: Identify meta directing groups.
The groups \(-CN\), \(-CO_2H\), and \(-CHO\) are electron withdrawing groups.
They withdraw electron density from the benzene ring through \(-R\) and \(-I\) effects.
Therefore, they are meta directing groups, not ortho and para directing groups.

Step 5: Select the correct set.
The ortho and para directing groups are:
\[ -OH,\;-OCH_3,\;-NHCOCH_3 \] That is:
\[ I,\;IV,\;V \]

Step 6: Final conclusion.
Hence, the correct answer is:
\[ \boxed{(1)\;I,\;IV,\;V} \]