Esters can react with amines in the same way they react with ammonia. Consider the following reaction. What product, aside from an alcohol, is formed from this reaction?
Let’s begin by examining the given equation. The first reactant is an ester. It contains the ester functional group, which is composed of one carbon-oxygen single bond and one carbon-oxygen double bond. The name of this ester is ethyl propanoate. The second reactant is an amine. It contains the amino group. And because the nitrogen atom is bonded to only one carbon-based group, it is a primary amine. The name of this amine is ethanamine. One of the products of this reaction is an alcohol. And we can recognize that this product is an alcohol because a hydroxy group is bonded to the carbon-based chain. The name of this alcohol is ethanol. This question is asking us to use our understanding of how esters react with ammonia to predict the other product of the reaction.
Esters react with ammonia in a reaction called ester ammonolysis. In the reaction, a primary amide and an alcohol are produced. Let’s write an equation for the ammonolysis reaction using the structural formula of the ester provided in the question and the structural formula of an ammonia molecule. When ammonia reacts with the ester, the carbon-oxygen single bond in the ester group breaks. The alkoxide portion of the ester becomes the alcohol product. The remaining part of the ester molecule joins with ammonia to form a primary amide. Recall that in a primary amide, the nitrogen atom is bonded to only one carbon-based group. It’s also important to recognize that this molecule contains the amide functional group, which is composed of a carbon-to-oxygen double bond and a carbon-to-nitrogen single bond.
Now let’s return to the reaction provided in the question. The provided reaction is an example of ester aminolysis. In the reaction, an ester reacts with a primary amine to form a secondary amide and an alcohol. We already have the structural formulas for the ester and the primary amine. And we have the structural formula for the alcohol product, ethanol. Using the pattern from the ammonolysis reaction, we’ll need to determine the structural formula of the other product. Just like in the ammonolysis reaction, the carbon-oxygen single bond of the ester group is going to break. The alkoxide portion of the ester becomes the alcohol. And the remaining portion of the ester combines with the amine to form the secondary amide.
How can we tell that this is a secondary amide? By closely examining the nitrogen atom, we see that it is bonded to two carbon-based groups. This secondary amide, which has the name N-ethylpropionamide, is the second product formed in the provided reaction.