Which structural change to compound 1 would make it more water soluble?

• A. Adding a bulky aromatic ring
• B. Replacing a polar group with a methyl group (${\mathrm{CH}}_3$)
• C. Increasing the length of the hydrocarbon chain
• D. Introducing a hydroxyl group ($\mathrm{OH}$) to the molecule

Answer: (D)

Verified step by step guidance

1. Understand that water solubility is largely influenced by the polarity of a molecule and its ability to form hydrogen bonds with water.
2. Recognize that adding a bulky aromatic ring increases hydrophobic character, which generally decreases water solubility.
3. Replacing a polar group with a methyl group (CH\3) reduces polarity and hydrogen bonding capacity, thus decreasing water solubility.
4. Increasing the length of the hydrocarbon chain adds more nonpolar, hydrophobic regions, which typically lowers water solubility.
5. Introducing a hydroxyl group (OH) adds a polar functional group capable of hydrogen bonding with water, thereby increasing the molecule's water solubility.