Question

Which one of the following fatty acids has the highest number of double bonds?

• A. Oleic acid
• B. Linoleic acid
• C. Linolenic acid
• D. Arachidonic acid

Hint:

Fatty Acid Double Bonds:
Oleic = 1
Linoleic = 2
Linolenic = 3
Arachidonic = 4
EPA = 5
DHA = 6.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Unsaturated fatty acid unsaturation degree is determined by the number of carbon-carbon ethylenic double bonds in the hydrocarbon tail.
Key Formula or Approach:
\[ \text{Oleic (18:1, } \Delta^9) \quad < \quad \text{Linoleic (18:2, } \Delta^{9,12}) \quad < \quad \text{Linolenic (18:3, } \Delta^{9,12,15}) \quad < \quad \text{Arachidonic (20:4, } \Delta^{5,8,11,14}) \]

Step 2: Detailed Explanation:
Comparing double bond counts in the given fatty acids:
1. Oleic Acid (18:1): 1 double bond (Monounsaturated, $\omega$-9).
2. Linoleic Acid (18:2): 2 double bonds (Polyunsaturated, $\omega$-6).
3. Linolenic Acid (18:3): 3 double bonds (Polyunsaturated, $\omega$-3 $\omega$-6).
4. Arachidonic Acid (20:4): 4 double bonds (all-cis-$\Delta^{5,8,11,14}$-eicosatetraenoic acid, $\omega$-6).
Therefore, Arachidonic acid has the highest number of double bonds.

Step 3: Final Answer:
Therefore, Arachidonic acid has the highest number of double bonds, matching option (D).