Triacylglycerol Reactions: Hydrolysis - Online Tutor, Practice Problems & Exam Prep

Triacylglycerol hydrolysis can occur via acid-catalyzed or enzymatic methods, producing glycerol and three fatty acids. Acidic hydrolysis involves strong acids like hydrochloric or sulfuric acid, breaking ester bonds stepwise. In contrast, saponification, a base-catalyzed hydrolysis using sodium hydroxide, yields glycerol and carboxylate anions, forming soap. The type of base determines the soap's form: solid with sodium hydroxide and liquid with potassium hydroxide. Understanding these reactions is crucial for applications in biochemistry and industrial processes.

Triacylglycerol Reactions: Hydrolysis Concept 1

In this video, we're going to take a look at a triacylglycerol reaction in the form of hydrolysis. Now, hydrolysis can be either acidic or basic. In this first video, we're going to look at acid-catalyzed hydrolysis. Now, under this type of reaction, an ester bond is hydrolyzed to create a glycerol molecule and three fatty acids. Now, here we're going to say it occurs stepwise in the presence of a strong acid. The acids are typically hydrochloric acid or sulfuric acid. When we say, stepwise, that means that all three fatty acids don't come off all at once. First, we do hydrolysis of the first ester linkage to break off the first fatty acid, then the second one occurs, and then the third one occurs. In this illustration here, we're going to show our final products as having three fatty acids. We're going to know that they all didn't come off all at once. This is the end result of going through three successions of acid-catalyzed hydrolysis to get rid of all three fatty acids.

Now, here if we take a look, we have our ester linkages here in red, we're using water and H⁺. Remember, hydrochloric acid and sulfuric acid are strong acids. In an aqueous environment, you typically see them represented as H⁺. You could still see H₂O over HCl or H₂O over H₂SO₄, but typically, again, we see these two strong acids in this form here. Now, what happens is our ester linkage is cut. So we cut these linkages. When we cut these linkages, the oxygen that is part of my glycerol molecule in blue, that oxygen gains a hydrogen. And in that way, we've created our OH groups for glycerol. So we've just created our glycerol molecule here. And then our fatty acid. Remember, a fatty acid has a hydrocarbon tail and then it has a carboxylic acid head. To make this into a carboxylic acid, we add OH to my carbonyl group. This is hydrolysis. We're using water to cut the ester linkage. We're basically adding water back. A H on the glycerol oxygens, OH on the carbonyl carbons.

Now, here besides acid-catalyzed hydrolysis, we have enzymatic hydrolysis. Now, this is a similar reaction done under milder conditions that instead uses the digestive enzyme lipase. So if we were to use the enzymatic approach, we'd use lipase instead of an acidic environment. This would still create our glycerol molecule and three fatty acids. We put it here because we're essentially making the same products. The pathway to get to them is different, but we're still making the same products at the end. So just remember, whether you're using acid-catalyzed hydrolysis or enzymatic hydrolysis, your products will be a glycerol molecule and three fatty acids.

Triacylglycerol Reactions: Hydrolysis Example 1

In this example question, it says, "Draw the fatty acid products for the following reaction." So, here we have our triacylglycerol molecule, or our triglyceride. We're using H₂ over our strong acid, hydrochloric acid. We know that, in essence, what happens here is that we're going to sever our ester linkages, the oxygens that are part of our glycerol molecule, they gain an H. And then these carbonyl groups here, they're going to gain OH groups to make our 3 fatty acids. So what we're going to do here is we're going to write them out, so we're going to have our OH's getting attached to these carbonyl groups. Right? So 1,2,3,4,5,6. There goes one fatty acid there. Let's see. 1,2,3. 1,2,3. And we have one here, and then we have this pi bond. There goes my other fatty acid. And then finally, we have here 1, 2, 3, 4, 5. 1, 2, 3, 4, 5. So those are my 3 fatty acids that I've made. Alright. So, we'd make this glycerol molecule here, and then these three individual fatty acids. They're all different from one another, so we don't have to draw them; we won't draw them all the same way. We have three distinct types of fatty acids within this certain product.

Provide the common name of the fatty acids produced from the enzymatic hydrolysis of the following triacylglycerol.

• A. Palmitoleic acid
• B. Lauric acid
• C. Palmitic acid
• D. Myristic acid

Triacylglycerol Reactions: Hydrolysis Concept 2

Now, saponification represents base-catalyzed hydrolysis. Because of this, we're going to say under this reaction, the hydroxide ion leaves the ester bond to create salts of the fatty acids and glycerol. If we take a look here, we have our ester linkages these red bonds here, they're going to be severed when we do saponification. We're using our Sodium Hydroxide and some heat in this case. We're going to add hydrogens to the oxygens that help to make the glycerol molecule and we're going to say here we're making salt of the fatty acids. That means we're not going to make carboxylic acid fatty acids, we're going to make carboxylate anions. So, basically, we're going to have negatively charged oxygens and because the metal that's formed with the base is Na, we have Na⁺ near it. So these will represent our 3 salts of the fatty acids. Now, here we're going to say the salts of the fatty acids are used in the creation of soaps. So this is one important application of saponification of a triglyceride molecule. It helps in the creation of soaps that we use. We're going to say here, when Sodium Hydroxide is used as our base, this helps to make a solid soap. And then if we use Potassium Hydroxide, KOH, that helps us to make liquid soap. So again, saponification represents base-catalyzed hydrolysis in this instance of a Triglyceride or Triacylglycerol molecule and we're going to say that it's important in the creation of soaps. And based on the type of base that you're using, you can either make hard soap, a solid soap, or you can make a liquid soap.

Triacylglycerol Reactions: Hydrolysis Example 2

This example question asks us to draw the starting Triacylglycerol used when its complete basic hydrolysis creates 2 Laurate Salts, 1 Palmitate Salt, and a Glycerol Molecule. Alright. So, here we're working backwards. First, we note that these 2 salts came from fatty acids. Here, the Laurate salt comes from Lauric acid, and the Palmitate salt came from Palmitic acid. Both of these fatty acids represent saturated fatty acids; Lauric acid has 12 carbons and no pi bonds, and Palmitic acid has 16 carbons and no pi bonds.

Now, working backwards, we start out with our glycerol base. So, we have CH₂CHCH₂, and these are connected to Oxygens to create our starting material. We're going to make Ester Linkages, so these Oxygens are connected to the carbonyls of these fatty acid chains. The first two will be Laurate Salts, each with 12 carbons: 2, 4, 6, 8, 10, 12. Repeat that sequence again: 2, 4, 6, 8, 10, 12. And then the last one is 16 carbons: 2, 4, 6, 8, 10, 12, 14, 16. This represents our starting material, our Triglyceride molecule or our Triacylglycerol molecule.

So again, we're just working backwards, knowing what the salt was in terms of its fatty acid form is essential to determine how many carbons it possesses and how many pi bonds it possesses. From there, we need to make Ester Linkages between the fatty acids and the glycerol base, which connects the fatty acids to it. Keep that in mind when asked to figure out what our starting material would be.

The salt of a fatty acid has its ending of “ic acid” changed to “ate”. Based on this information provide the name of the salt created from the following saponification reaction.

• A. Potassium Laurate
• B. Sodium Oleate
• C. Potassium Myristate
• D. Potassium Lactate

Here’s what students ask on this topic:

What is the difference between acid-catalyzed hydrolysis and base-catalyzed hydrolysis of triacylglycerols?

Acid-catalyzed hydrolysis of triacylglycerols involves breaking ester bonds using strong acids like hydrochloric acid (HCl) or sulfuric acid (H₂SO₄). This process occurs stepwise, producing glycerol and three fatty acids. In contrast, base-catalyzed hydrolysis, known as saponification, uses a strong base like sodium hydroxide (NaOH) or potassium hydroxide (KOH). This reaction yields glycerol and carboxylate anions, which form salts of fatty acids. The type of base used determines the form of soap produced: solid soap with NaOH and liquid soap with KOH.

How does enzymatic hydrolysis of triacylglycerols differ from acid-catalyzed hydrolysis?

Enzymatic hydrolysis of triacylglycerols uses digestive enzymes like lipase to break ester bonds under milder conditions compared to acid-catalyzed hydrolysis. While both methods produce glycerol and three fatty acids, enzymatic hydrolysis does not require strong acids and occurs at physiological pH and temperature. This makes enzymatic hydrolysis more suitable for biological systems, whereas acid-catalyzed hydrolysis is typically used in industrial processes.

What are the products of saponification, and how are they used?

Saponification, a base-catalyzed hydrolysis of triacylglycerols, produces glycerol and carboxylate anions, which form salts of fatty acids. These salts are used in the creation of soaps. The type of base used in saponification determines the form of soap: sodium hydroxide (NaOH) produces solid soap, while potassium hydroxide (KOH) produces liquid soap. These soaps are widely used in cleaning and personal care products.

Why is understanding triacylglycerol hydrolysis important in biochemistry and industrial processes?

Understanding triacylglycerol hydrolysis is crucial in biochemistry and industrial processes because it explains how fats are broken down into glycerol and fatty acids, which are essential for energy production and metabolic functions. In industrial processes, knowledge of hydrolysis is vital for producing soaps, detergents, and biodiesel. Acid-catalyzed and base-catalyzed hydrolysis methods are used to manipulate the chemical properties of fats for various applications, making this knowledge fundamental for both scientific research and practical applications.

What role do strong acids play in the acid-catalyzed hydrolysis of triacylglycerols?

In acid-catalyzed hydrolysis of triacylglycerols, strong acids like hydrochloric acid (HCl) or sulfuric acid (H₂SO₄) act as catalysts to break ester bonds. These acids provide H⁺ ions that facilitate the cleavage of ester linkages, resulting in the formation of glycerol and three fatty acids. The reaction occurs stepwise, with each ester bond being hydrolyzed sequentially. The strong acids ensure the reaction proceeds efficiently, making them essential for this type of hydrolysis.