Question

The functional group that shows negative resonance effect is:

• A. –NH\(_2\)
• B. –OH
• C. –COOH
• D. –OR

Answer 1

The Correct Option is C

To identify the functional group with a negative resonance effect, understanding resonance effects in organic chemistry is necessary. Resonance effects describe how substituents influence electron distribution within a molecule.

A negative resonance effect, denoted as -R, occurs when a substituent withdraws electrons via resonance. This typically happens when the substituent possesses a group that can delocalize electrons away from the attached ring or system.

Let's examine the provided options:

• –NH₂: The amine group donates electrons through resonance, owing to the nitrogen atom's lone pair. This effect is positive (+R).
• –OH: Similarly, the hydroxyl group donates electrons via resonance due to the oxygen atom's lone pair, resulting in a positive resonance effect (+R).
• –COOH: The carboxylic acid group withdraws electrons through resonance because the carbonyl carbon can participate in resonance, reducing electron density in the attached system. Consequently, it exhibits a negative resonance effect (-R).
• –OR: The alkoxy group (-OR) acts like –OH, donating electrons via resonance from the oxygen's lone pair, thus showing a positive resonance effect (+R).

Based on this analysis, the –COOH group is the correct answer as it demonstrates a negative resonance effect by delocalizing electron density away from its point of attachment.

Therefore, the correct option is: –COOH.