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Ch.15 Lipids
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
All textbooksTimberlake 13th EditionCh.15 LipidsProblem 91a
Chapter 15, Problem 91a

1.00 mole of glyceryl trioleate (triolein) is completely hydrogenated.
a. Draw the condensed structural formula for the product.

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1
Understand the problem: Glyceryl trioleate (triolein) is a triglyceride containing three oleic acid residues. Oleic acid is a monounsaturated fatty acid, meaning it contains one double bond in its hydrocarbon chain. Hydrogenation involves adding hydrogen (H₂) to the double bonds, converting them into single bonds.
Identify the structure of glyceryl trioleate: The molecule consists of a glycerol backbone esterified with three oleic acid chains. Each oleic acid chain has the formula CH₃(CH₂)₇CH=CH(CH₂)₇COO-. The double bond in each chain is located between the 9th and 10th carbon atoms (counting from the carboxyl group).
Determine the effect of hydrogenation: During complete hydrogenation, the double bonds in the oleic acid chains are converted into single bonds by the addition of hydrogen atoms. This changes the unsaturated fatty acid (oleic acid) into a saturated fatty acid (stearic acid). The new formula for each chain becomes CH₃(CH₂)₁₆COO-.
Draw the condensed structural formula for the product: Replace the oleic acid chains in glyceryl trioleate with fully saturated stearic acid chains. The resulting product is glyceryl tristearate, which has the condensed structural formula: CH₂(OCOC₁₇H₃₅)CH(OCOC₁₇H₃₅)CH₂(OCOC₁₇H₃₅).
Verify the product: Ensure that all double bonds have been removed and replaced with single bonds, and that the structure reflects the complete hydrogenation of glyceryl trioleate into glyceryl tristearate. This confirms the product is fully saturated.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hydrogenation

Hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to an unsaturated compound, typically an alkene or alkyne, converting it into a saturated compound. In the case of glyceryl trioleate, which contains multiple double bonds, hydrogenation will result in the conversion of these double bonds into single bonds, leading to a fully saturated fat.
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Glyceryl Trioleate Structure

Glyceryl trioleate, also known as triolein, is a triglyceride composed of glycerol and three oleic acid molecules. Its structure features a glycerol backbone with three long hydrocarbon chains (fatty acids) attached via ester linkages. Understanding its condensed structural formula is essential for visualizing how hydrogenation alters its molecular structure.
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Condensed Structural Formula

A condensed structural formula is a way of representing a chemical compound that shows the arrangement of atoms and the connectivity between them without depicting all the bonds explicitly. It provides a simplified view of the molecule, making it easier to understand the overall structure and functional groups present, which is crucial for drawing the product of the hydrogenation reaction.
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Related Practice
Textbook Question

One of the triacylglycerols in olive oil is glyceryl tripalmitoleate (tripalmitolein).

a. Draw the condensed structural formula for glyceryl tripalmitoleate (tripalmitolein).

Textbook Question

A sink drain can become clogged with solid fat such as glyceryl tristearate (tristearin).

c. How many milliliters of a 0.500 M NaOH solution are needed to completely react with 10.0 g of glyceryl tristearate (tristearin)?

Textbook Question

Match the lipoprotein (1 to 4) with its description (a to d).

1. chylomicrons

2. VLDL

3. LDL

4. HDL

b. “bad” cholesterol