A fundamental difference between aldehydes and ketones is that one can be oxidized to carboxylic acids but the other cannot. Which is which? Give an example of a test to differentiate aldehydes from ketones.

Question

Accepted Answer

Hello, everyone. Today we have the following problem, aldehydes or ketones, which can be oxidized to carboxylic acids. What tests are used to differentiate a sample of aldehyde from a sample of ketone? And then we have and choices A third D with A and B saying that aldehydes can be oxidized to carboxylic acids. And C and D saying that ketones can be oxidized to carboxylic acids. So, if we make note of the structure of an aldehyde, we know that if it undergoes oxidation, that we can form what is referred to as a carboxylic acid. And we'll explain why that happens in a bit. However, if we were to use a ketone and have it undergo oxidation, we would see that this would actually form no such reaction. And so why is that? Well, it's important to know that mild oxidizing oxidizing agents are used to differentiate between these two and why aldehydes are easily oxidized whereas ketones are unreactive. So one of the tests that are used is known as a Talens test and this Tollins test uses a variety of reagents such as silver oxy has ammonia, it has some water and it has some heat. And so essentially, this oxidizes the aldehyde to a carboxylic acid while the silver is reduced to a metal. And so this solution with the Ta tale reagent is colorless. And a positive test results in the formation of a metallic silver precipitate. And so, looking at our answer choices, we can see that C and D can be eliminated because aldehydes can be oxidized to carboxylic acids. Now, our answer will be b but let's explore the second test, which is known as the Benedicts Test. And, and the Benedict Benedict's test. It is simply using copper as a reagent, aqueous copper to be exact. And so essentially, the aldehyde is oxidized. So the carboxylic acid, while the copper is reduced, forming copper oxide. And so essentially, we can say that and B is correct that aldehydes can be oxidized to carboxylic acids. And the Tale test and the Benedict tests are used to differentiate a sample of aldehyde from a sample of ketone aldehydes will show a positive result while ketones generally show no reaction. And this is due to the mild oxidizing oxidizing reagents overall, I hope this helped. And until next time.

A fundamental difference between aldehydes and ketones is that one can be oxidized to carboxylic acids but the other cannot. Which is which? Give an example of a test to differentiate aldehydes from ketones.

Verified video answer for a similar problem:

Key Concepts

Aldehydes

Ketones

Oxidation Tests