See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: The solubility of alcohols in water depends on the balance between the hydrophilic hydroxyl (-OH) group and the hydrophobic alkyl chain. As the length of the carbon chain increases, the hydrophobic character of the molecule increases, making the alcohol less soluble in water. Reasoning: - All four alcohols contain one -OH group, which can form hydrogen bonds with water, contributing to solubility. - As the alkyl chain grows longer, the nonpolar hydrocarbon portion dominates, reducing the ability of water molecules to solvate the molecule effectively. - Ethanol (2 carbons): completely miscible with water. - 1-Propanol (3 carbons): highly soluble in water. - 1-Butanol (4 carbons): moderately soluble (~7.7 g/100 mL at 20°C). - 1-Pentanol (5 carbons): least soluble among the four (~2.2 g/100 mL at 20°C), because the longer nonpolar chain overwhelms the polar -OH group's ability to interact with water. Why other options fail: - Ethanol (a) is completely miscible with water — most soluble. - 1-Propanol (b) is highly soluble — second most soluble. - 1-Butanol (c) is less soluble than propanol but more soluble than 1-pentanol. - 1-Pentanol (d) has the longest carbon chain and therefore the greatest hydrophobic character, making it the least soluble. Therefore, the correct answer is D.