Video Transcript
The hydrolysis of a long-chain triester is shown. Which of the following is another name for this process? (A) Cleavage, (B) esterification, (C) polymerization, (D) saponification, or (E) hydrogenation.
Let’s start by defining each of the possible answer choices, starting with (A) cleavage. In chemistry, the term “cleavage” refers to the breaking of a chemical bond in a molecule. The cleavage of a chemical bond can happen in two ways. But this type of reaction can be readily identified when the bond between two atoms is broken, giving two fragments. The process of cleavage can occur one of two ways. In the process of homolysis, the two electrons in a cleaved covalent bond are divided equally between the products, creating two radicals. In the process of heterolysis, the bond breaks in such a fashion that the shared pair of electrons remains with only one of the fragments. However, the process of cleavage is the breaking of a covalent bond within a single molecule to form two or more smaller molecules. So we know answer (A) cannot be correct.
An esterification reaction is the reaction of an alcohol with a carboxylic acid to give an ester. This ester product has the general formula of RCOOR prime. And this general formula corresponds to the starting material of the hydrolysis of a long-chain triester, not the product. Therefore, we can eliminate answer choice (B).
A polymerization reaction is a reaction in which molecules, also known as monomers, join together to form long chains of repeating units called polymers. And although there are many types of polymerization reactions, the consistent aspect of polymerization reactions is that single monomers will form repeating units or long-chain molecules. In the reaction above, however, we are hydrolyzing a larger molecule into multiple smaller molecules. And so we know that answer choice (C) cannot be the correct answer.
A saponification reaction is a type of chemical reaction involving the base-induced hydrolysis of fats, oils, or other lipids into soaps and alcohols. And a soap is the salt of a fatty acid, otherwise known as a long-chain carboxylic acid. Looking at the reaction above, the long-chain triester is a type of fat. And the triester is reacting with NaOH, which is a base. And the reaction products are both a soap and an alcohol. And so this means that a saponification reaction is likely another name for the hydrolysis of a long-chain triester.
To confirm our answer, let’s look at answer choice (E). A hydrogenation reaction is the chemical reaction between molecular hydrogen, or H2, and another compound. One common example of a hydrogenation reaction is where one molecule of molecular hydrogen is added to a carbon-carbon double bond. This reaction results in the formation of two new carbon-hydrogen bonds. And since neither of our starting materials are molecular hydrogen, we can easily identify that answer choice (E) cannot be the correct answer. And so this confirms that our correct answer is answer choice (D) saponification.
