Open Question
Among the ingredients in lipstick are beeswax, carnauba wax, hydrogenated vegetable oils, and glyceryl tricaprate (tricaprin).
a. What types of lipids are these?
23. Lipids
Waxes
3:34 minutesProblem 20
Textbook Question
Draw the condensed structural formula for the ester in jojoba wax that is formed from arachidic acid, a 20-carbon saturated fatty acid, and 1-docosanol, CH3–(CH2)21–OH.
Verified step by step guidance1
Understand the structure of the ester: Esters are formed through a condensation reaction between a carboxylic acid and an alcohol. In this case, the carboxylic acid is arachidic acid (a 20-carbon saturated fatty acid), and the alcohol is 1-docosanol (a 22-carbon alcohol).
Write the condensed structural formula for arachidic acid: Arachidic acid has the formula CH₃—(CH₂)₁₈—COOH. This represents a 20-carbon chain with a carboxylic acid (-COOH) functional group at the end.
Write the condensed structural formula for 1-docosanol: 1-docosanol has the formula CH₃—(CH₂)₂₁—OH. This represents a 22-carbon chain with a hydroxyl (-OH) group at the end.
Combine the two molecules to form the ester: The esterification reaction involves the -OH group of the carboxylic acid (arachidic acid) reacting with the -H of the hydroxyl group (1-docosanol), resulting in the formation of water (H₂O) and an ester bond (-COO-).
Write the condensed structural formula for the ester: The ester will have the structure CH₃—(CH₂)₁₈—COO—(CH₂)₂₁—CH₃. This represents the 20-carbon chain from arachidic acid bonded to the 22-carbon chain from 1-docosanol through the ester functional group (-COO-).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Esterification
Esterification is a chemical reaction between an alcohol and a carboxylic acid, resulting in the formation of an ester and water. In this process, the hydroxyl group (-OH) from the acid and a hydrogen atom from the alcohol combine to release water, while the remaining parts form the ester bond. Understanding this reaction is crucial for drawing the structural formula of esters, such as those found in jojoba wax.
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Fatty Acids
Fatty acids are carboxylic acids with long hydrocarbon chains, which can be saturated or unsaturated. Arachidic acid, mentioned in the question, is a saturated fatty acid with 20 carbon atoms. Recognizing the structure and properties of fatty acids is essential for understanding how they interact with alcohols to form esters, particularly in biological and industrial contexts.
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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 in a molecule without depicting all the bonds explicitly. It provides a simplified view of the molecular structure, making it easier to visualize the connections between atoms. For the ester formed from arachidic acid and 1-docosanol, drawing the condensed structural formula will help illustrate the ester bond and the overall molecular composition.
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