Organic Chemistry : Help with Organic Lipids

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

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Example Question #11 : Help With Organic Lipids

The following terpene is classified as which of the following?

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Possible Answers:

Eicosanoid

Monoterpene

Hemiterpene

Diterpene

Monoterpenoid

Correct answer:

Monoterpene

Explanation:

The molecule's skeletal structure contains two isoprene (2-methylbutyl) units, and therefore the molecule is a monoterpene.

Example Question #12 : Biological Molecules

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Which of these two fatty acids has the lower melting point and why?

Possible Answers:

Alpha-linolenic acid, because it contains more cis double bonds.

Alpha-linolenic acid, because it contains fewer cis double bonds.

They have the same melting point since both have 18 carbons.

Stearic acid, because it contains more cis double bonds.

Stearic acid, because it contains fewer cis double bonds.

Correct answer:

Alpha-linolenic acid, because it contains more cis double bonds.

Explanation:

Fatty acids that contain a higher degree of unsaturation (more alkene bonds) will introduce more "kinks" into the hydrocarbon chain. This "kinked" chain does not stack nicely with other fatty acids of its kind and therefore are more likely to slip past each other at lower temperatures. This is primarily due to the van der Waals forces within the unsaturated fatty acids being disrupted with the introduction of double bonds. As a result, unsaturated fatty acids generally have a lower melting point than saturated fatty acids.

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