In this video, we're going to build up the knowledge to understand hemiacetals and hemiketals. Now before we actually define hemiacetal and hemiketal, it's first helpful to understand the reaction that results in cyclization of monosaccharides, and so monosaccharides, or sugars, can cyclize via a nucleophilic addition reaction that occurs between alcohol groups and the carbonyl groups of aldehydes or ketones. And so the alcohols in this reaction are going to be nucleophilic and so they will act as nucleophiles. Whereas the carbonyl groups of the aldehydes and ketones are electrophilic. So they are going to act as the electrophiles. And of course, the anomeric carbon is going to form upon cyclization of the monosaccharide. And so if we take a look at our example, we are going to see how alcohols can react with both aldehydes and ketones in order for a monosaccharide to cyclize. And so we can first analyze our image over here on the left and notice at the top here, we're just showing you this nucleophilic addition reaction that occurs between the alcohol and aldehyde. So notice here in orange, what we have is the alcohol group. And then, of course, over here in green, notice what we have is the aldehyde group. And so of course, the alcohol is going to be nucleophilic, so its electron density is going to attack the electrophilic carbonyl group of the aldehyde. And so of course, we're not showing the full mechanism that results upon monosaccharide cyclization, but this is the general idea that you guys should walk away with. Alcohols are nucleophilic, aldehydes are electrophilic. And so down below, notice that we're showing you a linear monosaccharide. And you can see that this linear monosaccharide has an aldehyde group and it has the alcohol group here, that is, needed for this nucleophilic addition reaction to take place. And so this is going to be an internal reaction that occurs within the same molecule. And ultimately, this results in this pyranose that we see over here when the C5 alcohol group interacts with the carbonyl group on the C1 carbon. And so this is a pyranose again because it contains a 6-membered ring. And notice that upon cyclization of this monosaccharide, the anomeric carbon forms. And of course, the anomeric carbon, we know from our previous lesson videos is the only carbon atom that's attached directly to 2 oxygen atoms, the ring oxygen and the oxygen of one of its alcohol groups. Now what you'll also notice is that the anomeric carbon before cyclization used to be the carbon of the carbonyl group. And so really that's another way to think about the anomeric carbon, it's the carbon atom that used to be part of the carbonyl group. Now, over here in the right side box, notice that we have a very similar reaction, except this time we have the alcohol group reacting with a ketone group instead of an aldehyde. And so again, the only difference between the aldehyde and ketone is that the ketone has the R group whereas the aldehyde has the Hydrogen. And so when we take a look at our linear monosaccharide here, notice that it contains both the ketone group and it contains the alcohol group. And so, this reaction is able to take place internally within the same monosaccharide and that results in the cyclization of the monosaccharide to form this furanose. And recall it's a furanose because it's a 5-membered ring when the C5 hydroxyl group interacts with the C2 ketone group. And of course upon cyclization, the anomeric carbon forms and, the anomeric carbon you can see is bound to 2 oxygen atoms directly and it used to be the carbon that was part of the carbonyl group. And so now that we have a better understanding of the reaction, that results in cyclization of monosaccharides. In our next video, we can distinguish between Hemiacetal and Hemiketal. So, I'll see you guys in that video.