Solubility trend in alcohols: Which of the following alcohols is most soluble in water at room temperature?

Introduction / Context:
Alcohol solubility in water depends on a balance between the hydrophilic hydroxyl group and the hydrophobic alkyl chain. As chain length increases, hydrophobic character increases and solubility generally decreases.

Given Data / Assumptions:

• Temperature near ambient.
• Normal liquid–liquid miscibility considerations.
• No salt or cosolvent effects.

Concept / Approach:
Short-chain alcohols (methanol, ethanol) are completely miscible with water due to strong hydrogen bonding and favorable entropy of mixing. With increasing carbon number, the nonpolar surface area increases, diminishing the thermodynamic favorability of hydration and reducing solubility.

Step-by-Step Solution:
Rank by chain length: methanol < ethanol < butanol < octanol < decanol. Shorter chain → stronger relative OH influence → higher solubility. Therefore, methanol is the most soluble among the choices. Ethanol is also highly soluble but slightly less than methanol.

Verification / Alternative check:
Data tables show methanol and ethanol are miscible; butanol has limited solubility; octanol and decanol are poorly soluble and form separate phases.

Why Other Options Are Wrong:
Increasing hydrophobic tail reduces water miscibility for butanol, octanol, decanol.

Common Pitfalls:
Assuming the presence of a polar group guarantees high solubility irrespective of chain length; ignoring temperature dependence and branching effects.

Final Answer:
Methanol (CH3OH).