Preparation of Dinitrogen Trioxide for Organic Synthesis: A Phase Equilibrium Approach.

Dinitrogen trioxide (NO) is a potent nitrosating agent featured with high reactivity and appealing atom economy. Because of its instability and the entanglement of chemical and phase equilibria, NO has rarely been utilized in organic synthesis as a stock reagent with well-defined composition. In this review, the preparations of pure NO and its concentrated solution (>0.1 M) are discussed from the aspect of phase equilibrium. Understanding the physical and chemical characteristics of NO, along with how reaction parameters (temperature, pressure, molar ratio) interact, plays a crucial role in managing the concentration of NO in the liquid phase. This control holds practical significance in achieving quantitative reactions.