What's up? In this video, we're going to talk about a carbonyl site reaction of monosaccharides called osazones. So guys, one of the reasons that you've got to love monosaccharides is because they have so many functional groups. They have so many alcohols, they have carbonyls. And in this video, we're going to talk about a specific reaction that happens to the carbonyl of a monosaccharide. It turns out that aldose aldehydes, so the aldehydes at the top of an aldose, are susceptible to the same exact nucleophilic addition reactions that we learned back for carbonyl chemistry. Okay? So you can't forget those reactions. Those reactions are very relevant to monosaccharides because monosaccharides will have carbonyls that can react in those reactions.
Do you guys remember what would happen when you expose a ketone or an aldehyde to a primary amine in acid? What you would get is an imine. You would get a functional group called an imine that had a double bond to the carbon. Okay? Now, remember that similarly, if you exposed a carbonyl to a primary amine derivative, meaning it's not exactly ammonia, it's not exactly a primary amine, maybe it has some group on it like alcohol or a benzene ring or something like that, that benzene ring would stick off the end, but you would still get an imine. So that product would be called an imine derivative. And guys, if you're getting a little bit lost by what I'm saying, maybe you've just started watching this chapter. I have a whole section in carbonyl chemistry talking about imines and imine derivatives. Okay? You can go back and watch all those videos.
Anyway, what I'm trying to do is remind you of what we already know so that we can move on and understand osazones. So when the specific primary amine derivative Phenylhydrazine is used, the product is referred to as a Phenylhydrazone, and these are again things we've already discussed from the carbonyl chemistry chapter. So when I talk about Phenylhydrazine, what I'm talking about is this molecule right here. Now this is called a primary amine derivative. Why? Because notice I have a primary amine here. This is a nitrogen with 2 H's and 1 benzene ring as a Z group instead of a usual R group. Okay?
Now, let's move to what happens if you react a primary amine derivative with the carbonyl in acid. According to our rules of using an imine derivative, we should expect a double bond from the nitrogen to the carbon with the benzene ring coming off. So, let's plug that in. What we would get is a double bond N with another N and the benzene ring. And this N, the attached nitrogen, requires an H to complete its 3 necessary bonds. This is what we would expect even if I hadn't taught you anything new, if you had just seen this reagent with acid a carbonyl, you should know from carbonyl chemistry that the aldehyde would make a Phenylhydrazone or a Phenylhydrazone derivative because in this case, it's not just a Phenylhydrazone; it has a sugar attached to it.
But now, this is where things get interesting. When exposed to additional equivalents of Phenylhydrazine, meaning that instead of just using a 1:1 mole ratio, what if we use 3 moles or excess moles of Phenylhydrazine? Your imine derivative, the phenylhydrazone derivative, is going to continue to tautomerize and react. The resulting product is going to be something utterly new, completely new that you've never learned before, and that's why we need to learn it here. That product is a C1, C2 Diphenylhydrazone derivative that we call an osazone.
Last point—this reaction was very important for Emil Fischer, who's really the father of carbohydrate chemistry. In 1888, he used osazones to prove that glucose and mannose were epimers of each other. Surprisingly, these compounds were very toxic; he ended up dying because he was exposed to so much Phenylhydrazine and osazones in his experiments that he developed cancer. But his legacy is tremendous, as his discoveries in sugar chemistry paved the way for identifying monosaccharide structures long before modern techniques were available. We don't use osazones much now, but their role in scientific history is why they continue to be taught.
Awesome, guys. So hopefully this made sense. Let's go ahead and move on to the next video.