However, because there happens to be a hydroxyl group on C 1 , the carbonyl can form here as well as at C 2 . Notice that DHAP is achiral while GAP is chiral, and that a new chiral center is introduce...However, because there happens to be a hydroxyl group on C 1 , the carbonyl can form here as well as at C 2 . Notice that DHAP is achiral while GAP is chiral, and that a new chiral center is introduced at C 2 . The catalytic base abstracts the pro-R proton from behind the plane of the page, then gives the same proton back to C 2 , again from behind the plane of the page.