THE STORY OF O

摘要

Everything in oxygen chemistry seemed more or less in place: Up there, in the stratosphere, there were oxygen atoms, O_2 molecules and ozone, O_3, as well as ions derived from these and a bit of active OH, all in a dance of creation and destruction. Meanwhile, within our bodies, normal O_2 served us well. There was even a place, under enzyme supervision, for the somewhat nasty relatives hydrogen peroxide (H_2O_2 and its deproto-nated form, O_2~(2-)) and superoxide (Of and its pro-tonated alter ego, HOO·), whose chemistry may generate the harmful hydroxyl radical OH·. Of course, there's also water everywhere. And here and there singlet dioxygen, a more reactive and excited state of normal diatomic oxygen. A nice, neatly compartmentalized world: ozone for atmospheric chemists, but not biologists, who had plenty of more complicated molecules to worry about. So they thought. This complacent state has now changed―dramatically so―with a series of remarkable discoveries. There is new evidence for the occurrence of ozone in living cells. Hydrogen peroxide is being made by molecules thought incapable of doing so. Even a metastable laboratory curiosity, the unusual HOOOH molecule (which sounds like a holler; call it dihydrogen-trioxide), may be in living systems. Meanwhile, we are still puzzling out the state of oxygen in high-temperature superconductors. And the menagerie of alternative forms of elemental oxygen continues to expand―there are strong theoretical arguments for the existence of a cyclic ozone isomer, and there may even be ways of stabilizing it.