Hydroxy group

Fischer projections are drawn so the highest priority group is closest to the top of the diagram – the aldehyde of an aldose or the ketone of a ketose.

Then, the H and OH groups are placed on specific sides of the chiral carbons.

If I build this with a model kit and point all of the horizontal bonds toward me, the carbon backbone starts to curl around to form a ring.

the structure isn't actually linear.

So even though it's a linear representation, we can use the Fischer projection to draw cyclic structures, too.

Before we start drawing rings, though, there's one more nomenclature thing to learn.

If the OH group on the bottom-most chiral carbon of the Fischer projection is on the right, it's a D sugar with a capital D.

And if it's on