heptoxide

Heptoxide refers to chemical compounds that contain seven oxygen atoms in each molecule. The best-known member is dinitrogen heptoxide, N2O7, an oxide of nitrogen that is a powerful oxidizer and a potential nitrating agent. In general, compounds called heptoxides are rare and typically highly reactive or unstable; nitrogen-based heptoxide is by far the most studied example.

Dinitrogen heptoxide (N2O7) is commonly described as comprising two nitro­gen atoms connected to seven oxy­gen atoms, often depicted as two NO3 groups linked by an oxygen bridge (O3N–O–NO3). It is a colorless, fuming liquid under ambient conditions and is highly hygroscopic, reacting readily with water. It hydrolyzes to form nitric acid (N2O7 + H2O → 2 HNO3) and can decompose exothermically, with increased sensitivity to heat, shock, and impurities. Because of its strong oxidizing character, N2O7 reacts violently with many materials, especially organic compounds, and its handling requires stringent precautions.

Preparation and uses of N2O7 typically involve dehydration chemistry. It can be generated in dry, highly acidic systems by removing water from nitric acid with strong dehydrating agents or within nitrating mixtures under carefully controlled conditions. Due to its instability, it is not widely used on an industrial scale, but it has historical relevance as a nitrating agent and a subject of inorganic-chemistry study.

In summary, heptoxide describes seven-oxygen species, with dinitrogen heptoxide as the principal example, notable for its high reactivity, hydrolysis to nitric acid, and role in chemical research.