According to general solubility rules, which of the following groups is most soluble in water when the masses and number of carbons are equivalent?

• A. Methyl group (–CH_3)
• B. Hydroxyl group (–OH)
• C. Phenyl group (–C_6H_5)
• D. Carboxyl group (–COOH)

Answer: (B)

Verified step by step guidance

1. Understand that solubility in water depends largely on the polarity of the group and its ability to form hydrogen bonds with water molecules.
2. Recall that water is a polar solvent, so polar or ionic groups tend to be more soluble due to favorable interactions like hydrogen bonding or dipole-dipole interactions.
3. Analyze each group: the methyl group (–CH_3) is nonpolar and hydrophobic, so it has low solubility in water.
4. The phenyl group (–C_6H_5) is also largely nonpolar and hydrophobic, leading to low solubility in water.
5. The hydroxyl group (–OH) is polar and can form hydrogen bonds with water, greatly increasing solubility compared to nonpolar groups.