The melting point of lipids depends on the strength of the intermolecular forces present in the solid.Rank the following fatty acids in order of $\underline{\text{ increasing }}$ melting point.

CH₃(CH₂) ₁₆CO₂H CH₃(CH₂) ₁₄CO₂H CH₃(CH₂) ₁₁CO₂H

Question

The melting point of lipids depends on the strength of the intermolecular forces present in the solid.Rank the following fatty acids in order of $\underline{\text{ increasing }}$ melting point. CH₃(CH₂)₁₆CO₂H CH₃(CH₂)₁₄CO₂H CH₃(CH₂)₁₁CO₂H A) CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₆CO₂H B) CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₆CO₂H C) CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₆CO₂H < CH₃(CH₂)₁₁CO₂H D) CH₃(CH₂)₁₆CO₂H < CH₃(CH₂)₁₄CO₂H < CH₃(CH₂)₁₁CO₂H E) CH₃(CH₂)₁₁CO₂H < CH₃(CH₂)₁₆CO₂H < CH₃(CH₂)₁₄CO₂H

Quizplus · Accepted Answer

The melting point of a fatty acid chain depends on the strength of the intermolecular forces, which are determined by the length of the chain and the degree of unsaturation. In this case, all the fatty acid chains have the same degree of saturation (no double bonds) but differ in length. The longer the chain, the stronger the intermolecular forces and the higher the melting point. Therefore, the order of increasing melting point should be based on the length of the chain, from shortest to longest. Based on the given formulas, the order of increasing chain length is: CH3(CH2)10COOH < CH3(CH2)11COOH < CH3(CH2)12COOH. Therefore, the correct ordering from lowest to highest melting point is:
CH3(CH2)10COOH < CH3(CH2)11COOH < CH3(CH2)12COOH.
Choice A is the only option that correctly follows this pattern.

The Melting Point of Lipids Depends on the Strength of the Intermolecular