Question

Write structural formulas for the following. (a) glyceryl palmitolauroeleostearate (b) tripalmitin (c) potassium myristate (d) butyl oleate

Short answer

Step-by-step structures have been drawn as per given names; (a) glyceryl palmitolauroeleostearate is a triglyceride structure with one each of palmitate, laurate and eleostearate attached to the glycerol backbone. (b) Tripalmitin is a triglyceride with all three fatty acids being palmitate. (c) Potassium myristate is the potassium salt of myristic acid. (d) Butyl oleate is an ester formed by butyric acid and oleic acid.

Step-by-step solution

Understanding the Nomenclature

In the name 'glyceryl palmitolauroeleostearate', 'glyceryl' indicates a glycerol backbone, while 'palmitate', 'laurate' and 'eleostearate' are fatty acids attached to the glycerol backbone. Similarly analyze the rest of the parts. 'Tripalmitin' indicates a glycerol backbone with three 'palmitate' fatty acids attached. 'Potassium myristate' is a salt of myristic acid and potassium. 'Butyl oleate' indicates an ester of butyric acid and oleic acid.

Visualizing Fatty Acids

For example, palmitate is a 16-carbon fatty acid, laurate is a 12-carbon fatty acid, and eleostearate is an 18-carbon fatty acid with three cis double bonds. Oleate is also an 18-carbon fatty acid with one cis double bond at the 9th carbon. Myristate is a 14-carbon fatty acid. Butyric acid is a 4-carbon fatty acid. Define these fatty acids for the additional parts.

Drawing Structure for (a)

Draw the glycerol backbone, which is a three-carbon structure. To each hydroxyl group of the glycerol backbone, connect a carboxyl group of the fatty acids: palmitate, laurate and eleostearate respectively.

Drawing Structure for (b)

Draw the glycerol backbone again and connect three palmitate fatty acids to each of its hydroxyl groups.

Drawing Structure for (c)

Draw the myristic acid with a 14-carbon chain and a carboxyl group at one end. Replace the hydrogen atom of carboxyl group with a potassium ion.

Drawing Structure for (d)

For butyl oleate, draw the 4-carbon chain of butyric acid and connect to the carboxyl group of oleic acid forming an ester linkage.

Key concepts

Chemical Nomenclature in Organic Chemistry

Chemical nomenclature is the systematic naming of chemical compounds following specific rules set by the International Union of Pure and Applied Chemistry (IUPAC). In organic chemistry, this nomenclature helps identify the structure of organic molecules, such as lipids and esters, through the names of the compounds.

In the given exercise, names such as 'glyceryl palmitolauroeleostearate' break down into parts that each describe a different component of the molecule. 'Glyceryl' refers to the alcohol, glycerol, indicating its presence in the molecule. The rest, 'palmitolauroeleostearate,' signifies different fatty acids named 'palmitic,' 'lauric,' and 'eleostearic' acids. This systematic approach enables chemists to recognize and construct complex structures simply from a compound's name, showcasing the power and importance of chemical nomenclature in the scientific community.

The Glycerol Backbone in Lipids

The glycerol backbone is the foundation of many lipids, such as fats, oils, and phospholipids. It consists of a three-carbon alcohol structure, each carbon containing a hydroxyl group (OH). These hydroxyl groups can react with the carboxyl groups (COOH) of fatty acids to form ester linkages, creating triglycerides.

For instance, 'tripalmitin' from the exercise is a glycerol molecule esterified with three palmitic acid molecules, demonstrating how glycerol serves as a versatile scaffolding in lipid biology. This critical role in storing energy and providing insulation makes the glycerol backbone a fundamental concept in biochemistry and nutrition science.

Fatty Acids: Structure and Properties

Fatty acids are carboxylic acids with long hydrocarbon chains that can be either saturated or unsaturated. These chains consist of varying numbers of carbon atoms, which define the physical properties of the fatty acid, such as melting point and solubility.

The exercise names fatty acids of varying lengths, from 'palmitate' with 16 carbons to 'oleate' with an 18-carbon chain and a characteristic cis double bond at the 9th carbon. Understanding these chains and their functional groups is crucial for grasping how fatty acids interact within biological structures and how they contribute to the physical characteristics of lipids.

Ester Formation and Its Significance

Ester formation is a chemical reaction where a carboxylic acid and an alcohol combine to form an ester and water, typically catalyzed by an acid or base. This reaction is fundamental for creating fats, oils, and various synthetic compounds. In the context of our problem, 'butyl oleate' shows this process, combining butyric acid (a short-chain fatty acid) with oleic acid (a long-chain unsaturated fatty acid) to form the corresponding ester.

The ability to recognize and predict outcomes of esterification reactions is valuable for industries ranging from food processing to pharmaceuticals. Esters also have distinctive odors which make them key ingredients in fragrances and flavorings, highlighting the practical importance of understanding ester formation.