Q.32 Oleic acid, shown below, is
(A) A saturated fatty acid
(B) An unsaturated fatty acid
(C) Insoluble in water
(D) Soluble in acetoneOleic acid in this question is an unsaturated fatty acid that is insoluble in water but soluble in organic solvents like acetone.

Question and Correct Answer

Question:
Oleic acid, shown below, is:

(A) A saturated fatty acid
(B) An unsaturated fatty acid
(C) Insoluble in water
(D) Soluble in acetone

Correct answers:

• (B) An unsaturated fatty acid

• (C) Insoluble in water

• (D) Soluble in acetone

If the exam is single‑correct, the primary conceptual key is option (B), but chemically both (C) and (D) are also true statements about oleic acid.

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Explanation of Option (A): A saturated fatty acid

• A saturated fatty acid contains only carbon–carbon single bonds in its hydrocarbon chain, with no carbon–carbon double bond present.

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• Oleic acid has 18 carbons with one cis double bond at the 9th carbon (C18:1, cis‑9‑octadecenoic acid), so it is not saturated and therefore option (A) is incorrect.

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Explanation of Option (B): An unsaturated fatty acid

• Oleic acid is a monounsaturated omega‑9 fatty acid, with the notation C18:1 because it has one double bond in an 18‑carbon chain.

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• The presence of this C=C bond classifies it as an unsaturated fatty acid, making option (B) correct.

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Explanation of Option (C): Insoluble in water

• Long‑chain fatty acids like oleic acid have a single polar carboxyl group and a long nonpolar hydrocarbon tail, giving an overall strongly hydrophobic character.

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• As a result, oleic acid is practically insoluble in water at room temperature, so statement (C) is chemically correct.

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Explanation of Option (D): Soluble in acetone

• Oleic acid dissolves readily in many organic solvents such as ethanol, ether, chloroform, DMSO, and acetone because its long hydrophobic tail interacts favorably with these less polar media.

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• Therefore, option (D) is also a true statement: oleic acid is soluble in acetone.

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