Video Transcript
The presence and properties of an ester can usually be determined through its reactions with other types of molecules. Which of the following equations correctly represents the ammonolysis of an ester? (A), (B), (C), (D), or (E).
An ester is an organic molecule with the general formula of RCOOR prime, where the R group is a hydrogen, an alkyl group, or an aryl group and the R prime group is an alkyl group or an aryl group. And connecting the R and R prime substituents is the ester linkage, made up of a carbon with one double bond to oxygen and one single bond to oxygen.
An ammonolysis reaction is one where ammonia reacts with another molecule, breaking one or more bonds. When ammonia, or NH3, reacts with an ester, a new bond is made between the ammonia nitrogen and the carbon of the ester linkage. And the carbon-oxygen single bond of the ester linkage is then broken. And that’s because it’s the weakest of the bonds in the ester functional group. Importantly, both the R-to-carbon single bond and carbon-to-oxygen double bond are significantly stronger than the carbon-oxygen single bond in an ester group.
At this point, let’s look at a specific example and discuss what products are formed in an ammonolysis reaction. As we’ve already discussed, when ammonia reacts with an ester, the carbon-oxygen single bond of the ester linkage is broken and a new bond is formed between the carbon of the ester linkage and the ammonia nitrogen. And this reaction forms a primary amide with the formula RCONH2 and an alcohol with the formula R prime OH. It’s important to notice that the R group that’s bonded to the carbon of the ester linkage is the same R group that’s bonded to the carbon of the primary amide functional group. And that’s because the bond between the carbon and the R group is an extremely strong bond and won’t break in an ester ammonolysis reaction. You can also see that when the carbon-oxygen single bond of the ester linkage is broken, the OR prime group becomes the alcohol. And this will stay the same for all ester ammonolysis reactions.
And now with this information, we should be able to answer the question. The presence and properties of an ester can usually be determined through its reactions with other types of molecules. Which of the following equations correctly represents the ammonolysis of an ester? And since we know that we’re reacting an ester with ammonia, or NH3, and forming a primary amide, where the carbon of the amide is bonded to the R group, and an alcohol, where the oxygen is bonded to the R prime group, we can correctly choose answer choice (A). RCOOR prime plus NH3 react to form RCONH2 plus R prime OH.
