When considering the polarity of the five benzene derivatives: benzoic acid, salicylic acid, p-hydroxybenzoic acid, acetanilide, and p-aminophenol, we can predict their order of polarity based on the presence and strength of functional groups as well as their ability to hydrogen bond.
Here’s the predicted order of polarity from least to most polar:
- Acetanilide
- Benzoic Acid
- p-Hydroxybenzoic Acid
- Salicylic Acid
- p-Aminophenol
Explanation:
- Acetanilide: This compound has an amide functional group, but the presence of the methyl group makes it relatively non-polar compared to the others, limiting its ability to form strong intermolecular hydrogen bonds.
- Benzoic Acid: With a carboxylic acid group, benzoic acid is more polar than acetanilide. It can form hydrogen bonds, but it lacks additional polar functional groups that can enhance its polarity further.
- p-Hydroxybenzoic Acid: The presence of both the hydroxyl (-OH) group and the carboxylic acid (-COOH) group increases its polarity compared to benzoic acid. The two polar functional groups allow for intramolecular and intermolecular hydrogen bonding.
- Salicylic Acid: Similar to p-hydroxybenzoic acid, salicylic acid contains both -OH and -COOH groups. However, the additional hydroxyl group enhances its polarity, allowing for stronger hydrogen bonding due to both functional groups being able to participate in interactions with water.
- p-Aminophenol: This compound has an amino (-NH2) group and a hydroxyl (-OH) group. The amino group can participate in hydrogen bonding and has a strong electron-donating effect, increasing its electronegativity compared to the others, making it the most polar compound on this list.
This order reflects the influence of different functional groups on polarity, highlighting the role of their ability to engage in hydrogen bonding and their electron-withdrawing or donating effects.