Which of the following molecules is most likely to be soluble in water?

Butanol is the most likely to be soluble in water due to its molecular structure and polarity. It is an alcohol with a hydroxyl (-OH) functional group that significantly increases its ability to form hydrogen bonds with water molecules. This polar characteristic allows butanol to interact favorably with water, making it more soluble compared to non-polar molecules.

In contrast, hexane and octadecane are both hydrocarbons with long non-polar carbon chains, which result in very low solubility in water. Their hydrophobic nature makes them interact poorly with polar solvents like water. Cholesterol, while containing a hydroxyl group and being somewhat polar, has a large hydrophobic structure, making it more hydrophobic overall compared to butanol. As a result, butanol's size and polar functional group contribute to its solubility in water, distinguishing it from the other options.