Dinitrogen trioxide is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

N₂O₃. It is one of the simple

nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide * Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or ...

s. It forms upon mixing equal parts of

nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its ...

and

nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the productio ...

and cooling the mixture below −21 °C (−6 °F): :NO + NO₂ N₂O₃ Dinitrogen trioxide is only isolable at low temperatures, i.e. in the liquid and solid phases. In liquid and solid states, it has a deep blue color. At higher temperatures the equilibrium favors the constituent gases, with ''K''_diss = 193 kPa (25 °C). This compound is sometimes called "nitrogen trioxide", but this name properly refers to another compound, the (uncharged) nitrate radical .

Structure and bonding

Typically, N–N bonds are similar in length to that in

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

(145 pm). Dinitrogen trioxide, however, has an unusually long N–N bond at 186 pm. Some other nitrogen oxides also possess long N–N bonds, including

dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russia rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

(175 pm). The N₂O₃ molecule is planar and exhibits Cs symmetry. The dimensions displayed below come from microwave spectroscopy of low-temperature, gaseous N₂O₃: It is the anhydride of the unstable

nitrous acid Nitrous acid (molecular formula ) is a weak and monoprotic acid known only in solution, in the gas phase and in the form of nitrite () salts. Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagent ...

(HNO₂), and produces it when mixed into water. An alternative structure might be anticipated for the true anhydride, i.e. O=N–O–N=O, but this isomer is not observed. If the nitrous acid is not then used up quickly, it decomposes into nitric oxide and nitric acid. Nitrite salts are sometimes produced by adding N₂O₃ to solutions of bases: :N₂O₃ + 2 NaOH → 2 NaNO₂ + H₂O Here the oxidation state of one nitrogen is +3.

References

External links

National Pollutant Inventory – Oxides of nitrogen fact sheet

{{Oxides Nitrogen oxides Acidic oxides Acid anhydrides Sesquioxides