N2O4, or dinitrogen tetroxide, is a chemical compound composed of two nitrogen atoms and four oxygen atoms. It is a colorless gas at room temperature and can exist in equilibrium with its dimer, N2O4 and NO2, which is a reddish-brown gas. Dinitrogen tetroxide is commonly used in rocket propulsion as an oxidizer due to its ability to release oxygen when decomposed. This compound is also important in various industrial processes, including the production of nitric acid and as a reagent in organic synthesis. N2O4 is known for its role in atmospheric chemistry, where it can contribute to the formation of nitrogen oxides, which are pollutants that affect air quality.