Rank the following compounds in order of decreasing acidity based upon the Ka value, with being = the strongest acid and being the weakest acid. points) OH OH OH OH Rank the following compounds in order of decreasing basicity based upon the Kb value, with bcing – the strongest base and 3 being the weakest base points) NOz OH Rank the following compounds in order of decreasing boiling point with being the highest boiling point and 3 being the lowest boiling point. points) OH
The Correct Answer and Explanation is:
Here are the correct rankings and explanations for each question:
Question 3: Acidity Ranking (Ka values)
Compounds:
- Trichloroacetic acid
- Monochloroacetic acid
- Propanoic acid
- Butanoic acid
Ranking (Strongest to Weakest Acid):
1 > 4 > 2 > 3
Explanation:
Acidity depends on how stable the conjugate base is after deprotonation. Electron-withdrawing groups (EWGs) like chlorine stabilize the conjugate base via inductive effects, increasing acidity.
- Trichloroacetic acid (three Cl groups) has the strongest EWG effect, so it is the strongest acid.
- Monochloroacetic acid has one Cl, so it’s next.
- Propanoic acid has no EWG, but is still a carboxylic acid.
- Butanoic acid is similar to propanoic acid but with a longer alkyl chain that donates electrons, slightly decreasing acidity.
Question 4: Basicity Ranking (Kb values)
Compounds:
- 4-Nitropyridine
- 4-Hydroxypyridine
- 4-Methylpyridine
Ranking (Strongest to Weakest Base):
3 > 2 > 1
Explanation:
Basicity depends on the availability of the lone pair on the nitrogen atom. Electron-donating groups (EDGs) increase basicity, while EWGs decrease it.
- Methyl is an EDG, making 4-methylpyridine the strongest base.
- Hydroxyl has mixed effects; it is slightly electron withdrawing via resonance but donating via induction, placing it in the middle.
- Nitro is a strong EWG and pulls electron density away from the nitrogen, making 4-nitropyridine the weakest base.
Question 5: Boiling Point Ranking
Compounds:
- Ethyl methyl ether
- Propanoic acid
- Butanone
Ranking (Highest to Lowest Boiling Point):
2 > 3 > 1
Explanation:
Boiling point increases with stronger intermolecular forces.
- Propanoic acid can form hydrogen bonds and dimerize, giving it the highest boiling point.
- Butanone has dipole-dipole interactions but no hydrogen bonding.
- Ethyl methyl ether has only weak dipole-dipole and London dispersion forces, making it the lowest.
These rankings are based on molecular structure, electron effects, and intermolecular forces.
