Well, what this reaction is is basically a reaction between a nucleophile and an electrophile. The nuclear file in this case is an alcohol group on the sugar molecule, while the electrophile is the carbon of the carbonyl. And that can be either an aldehyde or a ketone, depending if we're looking at aldos or ketosis. So if we have an aldehyde group on that sugar molecule, well, then it reacts with an alcohol group on that same sugar molecule to form a hemicata. And likewise, if we have a ketone instead of the aldehyde, that ketone will act as the electrophile reacting with the nucleophile, one of the hydroxyl groups on that sugar molecule, to form a hemiketel. So let's begin by focusing on aldohexos.