Questions 14-16 refer to the following compounds. (A) CH3CH2CH2CH3 (B) CH3CH2CH2OH (C) CH3COCH3 (D) — Solutions Chemistry Question

STEPS:

1. Identify the Nature of the Solvent: Water is a highly polar molecule that is capable of forming extensive hydrogen bonds. According to the principle of "like dissolves like," substances that are polar or can form hydrogen bonds with water are generally soluble in it.
2. Evaluate Intermolecular Forces (IMFs): To determine solubility, analyze the types of IMFs each molecule can form with water molecules.
3. Analyze Choice A ($CH_3CH_2CH_2CH_3$): This molecule is a nonpolar hydrocarbon (butane). It consists only of carbon-carbon and carbon-hydrogen bonds, which share electrons relatively equally. Because it is nonpolar and lacks any atoms capable of hydrogen bonding, it only possesses weak London dispersion forces.
4. Compare Interactions with Water: While the other four options have polar functional groups that can interact strongly with water's dipoles or form hydrogen bonds, choice A has no way to attract water molecules effectively.
5. Conclusion: Because butane is nonpolar and cannot form hydrogen bonds, it has the weakest attraction to water molecules among the choices, making it the LEAST soluble in water.

WHY_OTHERS_WRONG:

• $CH_3CH_2CH_2OH$ (B), $CH_3COOH$ (D), and $CH_3CH_2CH_2NH_2$ (E): These molecules contain oxygen or nitrogen atoms bonded to hydrogen. These functional groups (alcohol, carboxylic acid, and amine) allow the molecules to be polar and form hydrogen bonds with water, significantly increasing their solubility.
• $CH_3COCH_3$ (C): This ketone is a polar molecule due to the $C=O$ double bond. While it cannot donate a hydrogen bond (since no hydrogen is attached directly to the oxygen), the oxygen atom can accept hydrogen bonds from water, making it quite soluble compared to a nonpolar hydrocarbon.