Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Nitrogen dioxide is the chemical compound with the formula NO2. One of several nitrogen oxides, NO2 is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent air pollutant. Nitrogen dioxide is a paramagnetic bent molecule with C2v point group symmetry.