Phenacetin is more polar than aspirin because of its molecular structure. Phenacetin has a polar functional group, the acetamide group (-CONH2), which makes the molecule more polar overall. This group has a positive charge on the nitrogen atom and a negative charge on the oxygen atom, making it a dipole, or a molecule with a positive and negative end.
In contrast, aspirin has a non-polar functional group, the acetyl group (-COCH3), which does not have a dipole moment. This makes aspirin less polar overall.
The polarity of a molecule affects its solubility in different solvents. Polar molecules are soluble in polar solvents, such as water, while non-polar molecules are soluble in non-polar solvents, such as oil. Phenacetin is more soluble in water because of its polar functional group, while aspirin is less soluble in water because of its non-polar functional group.
In summary, phenacetin is more polar than aspirin because it has a polar functional group, the acetamide group, while aspirin has a non-polar functional group, the acetyl group. This difference in polarity affects the solubility of the two molecules in different solvents.