But instead of having the aldehyde, we have this ketone group. And so now what takes place is this hydroxyl group on the fifth carbon. So this hydroxyl group on the fifth carbon here reacted with the first carbon. But in this case, this hydroxyl on the fifth carbon will react with the carbon that is number two, because this is the carbon of the carbonyl that will act as the electrophile. And so now, instead of forming a six member ring, instead of forming the pyramids, we're going to form a fewer nose, and this is a five membered ring. Why?