In a semiheavy water molecule, one hydrogen atom (H) is replaced with a heftier version called deuterium (D).
在半重水的水分子中，一个氢原子（H）被一个称之为氘（D）的氢原子的同位素所取代。
2
On a molecular level, D-tagatose is structurally identical to D-fructose, except for an inversion of the hydroxyl and hydrogen groups at the fourth carbon atom.