The HNO radical anion: A proposed intermediate in diazeniumdiolate synthesis using nitric oxide and alkoxides.

The strategy of synthesizing diazeniumdiolates (X-N(O)=NO) through the coexistence of nitric oxide and alkoxides (RO) was introduced by Wilhelm Traube 120 years ago. Today, despite the wide use of diazeniumdiolate derivatives to release nitric oxide in the treatment of cancer, the first step of the reaction mechanism for diazeniumdiolate synthesis remains a mystery and is thought to be complex. We have studied the gas-phase reactions of nitric oxide with alkoxides at room temperature. An electron-coupled hydrogen transfer is observed, and the radical anion HNO is the only ionic product in these reactions. HNO can further react with nitric oxide to form NO and HO.