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Assertion : Aromatic aldehydes and keton...

Assertion : Aromatic aldehydes and ketones undergo electrophilic substitution reaction at metaposition.
Reason : Carbonyl group activates the ring towards electrophilic substitution reactions.

A

If both assertion and reason are true and reason is the correct explanation of assertion.

B

If both assertion and reason are true but reason is not the correct explanation of assertion.

C

If assertion is true but reason is false.

D

If both assertion and reason are false.

Text Solution

AI Generated Solution

The correct Answer is:
To analyze the given assertion and reason, we will break down the concepts step by step. ### Step 1: Understanding the Assertion The assertion states that "Aromatic aldehydes and ketones undergo electrophilic substitution reaction at the meta position." - **Explanation**: In electrophilic aromatic substitution reactions, the position where the electrophile attacks the aromatic ring depends on the substituents already present on the ring. Aldehydes (–CHO) and ketones (–C=O, with an alkyl group) are both electron-withdrawing groups due to the electronegativity of the oxygen atom. This means they decrease the electron density of the aromatic ring, particularly at the ortho and para positions. ### Step 2: Understanding the Reason The reason states that "Carbonyl group activates the ring towards electrophilic substitution reactions." - **Explanation**: The carbonyl group (C=O) is actually a deactivating group in electrophilic aromatic substitution. It pulls electron density away from the aromatic ring, making it less reactive towards electrophiles. Therefore, the statement that it activates the ring is incorrect. ### Step 3: Analyzing the Effects of the Carbonyl Group When a carbonyl group is attached to an aromatic ring, it has the following effects: - It withdraws electron density from the ring due to the electronegativity of oxygen. - This withdrawal of electron density makes the ortho and para positions less favorable for electrophilic attack because these positions become electron-deficient. ### Step 4: Conclusion Since the carbonyl group deactivates the aromatic ring, the electrophile will preferentially attack the meta position, where the electron density is relatively higher compared to the ortho and para positions. ### Final Answer - **Assertion**: True (Aromatic aldehydes and ketones undergo electrophilic substitution at the meta position). - **Reason**: False (The carbonyl group does not activate the ring; it deactivates it). Thus, the correct conclusion is that the assertion is true while the reason is false.
To analyze the given assertion and reason, we will break down the concepts step by step. ### Step 1: Understanding the Assertion The assertion states that "Aromatic aldehydes and ketones undergo electrophilic substitution reaction at the meta position." - **Explanation**: In electrophilic aromatic substitution reactions, the position where the electrophile attacks the aromatic ring depends on the substituents already present on the ring. Aldehydes (–CHO) and ketones (–C=O, with an alkyl group) are both electron-withdrawing groups due to the electronegativity of the oxygen atom. This means they decrease the electron density of the aromatic ring, particularly at the ortho and para positions. ### Step 2: Understanding the Reason ...
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