So now that we're familiar with the reaction that allows monosaccharides to cyclize, in this video we're going to focus on how cyclization will form either a hemiacetal or a hemiketal. And so we already know from our last lesson video that the anomeric carbon will form upon monosaccharide cyclization. But what you may not have realized is that this anomeric carbon that forms will actually become part of a relatively unstable hemiacetal or hemiketal. Now, the prefix hemi is a prefix that means half, and so literally, hemiacetal can be defined as half of an acetal group. And so this is going to result from the reaction that we talked about in our last lesson video, which was an alcohol reacting with an aldehyde group. And then, of course, a hemiketal can be defined as half of a ketal group. And this is going to result from again, the same reaction we talked about in our last lesson video, which is an alcohol group reacting with a ketone group.

If we take a look at our example image down below, we can distinguish between hemiacetals and hemiketals. So in this box here, notice that the top half is showing the formation of a hemiacetal and the bottom half of our image is showing the formation of a hemiketal. And so what you'll notice is that the hemiacetal and hemiketal are resulting from the same exact reaction we talked about in our last lesson video, which is an alcohol group reacting with an aldehyde group will form this hemiacetyl and of course, an alcohol group reacting with a ketone group will form the hemiketal. Moreover, one thing that's interesting to note here is that the only difference between the aldehyde and the ketone is actually the difference that we see here, the hydrogen, and the R group. And really, when you take a look at it, the only difference between the hemiacetal and the hemiketal is the same exact hydrogen and R group. So notice that this hydrogen and this R group here is the only thing that makes the two different from each other.

So what you'll notice is that the carbon atom that we have highlighted here in the middle is the anomeric carbon. And again, the anomeric carbon is going to be part of either the hemiacetal or the hemiketal. And so, as we move forward through our course, we'll be able to easily distinguish them from each other. And really, it's just looking at the anomeric carbon and seeing if a hydrogen atom is attached or looking at the anomeric carbon and seeing if there's an R group attached. And so just to be clear here, you can think of these R groups as the rest of the carbon ring or the rest of the sugar structure, these R groups over here. Again, we're focusing on looking at these anomeric carbons here and just seeing if there is a hydrogen atom attached or if there is an R group attached.

So now that we've seen this, if we take a look at the previous image that we had up above from our previous lesson video, what you'll notice is that the anomeric carbon that we have here is a hemiacetal because notice that it has a hydrogen atom, just like the hemiacetal down here. And then notice over here on the right image, this is showing a hemiketal because going down, we have an R group, and so that is this R group that we have here. And again, as we move forward through our course, we'll be able to apply the concepts that we've learned here and you'll just get better and better at distinguishing between the Hemiacetal and the Hemiketal. So this concludes our lesson on the difference between a hemiacetal and a hemiketal, and I'll see you guys in our next video.