Nitrogen trioxide is an oxidizing gas used as a reagent in chemical synthesis and one of the most important propellants for rockets.

The name describes the structure of the molecule:

• Nitrogen is a non-metal with atomic number 7. It makes up about 78% of the Earth’s atmosphere and is a crucial element for life.
• Trioxide indicates that there are three oxygen atoms in the compound.
• "tri-" means three, and "oxide" refers to the oxygen component.

The synthesis process takes place in several stages:

• Formation of nitrogen dioxide (NO2): nitrogen dioxide can be formed by oxidation of nitric oxide (NO) in the presence of oxygen. This reaction is exothermic and releases heat.
• Dimerization of nitrogen dioxide: Two molecules of nitrogen dioxide can combine to form nitrogen trioxide. This is a reversible reaction and can be affected by changes in temperature or pressure.
• Purification: Nitrogen trioxide can be purified by distillation or other methods to remove any unreacted nitrogen dioxide or other impurities.

What it is for and where

Nitrogen trioxide is a useful compound in the chemical industry and is used in the production of nitric acid. It is also a significant pollutant in the atmosphere, contributing to the formation of smog and acid rain.

Studies

• Recent studies have proposed an interesting thesis: nitrite-hemoglobin produces, through a reaction, the Nitrogen trioxide (N2O3) that is sufficiently stable to release NO into human tissue (1).
• Autotrophic nitrifiers have been shown to produce nitrogen oxide and dinitrogen oxide under oxic conditions. Dinitrogen oxide is produced mainly during nitrite reduction (i.e. aerobic denitrification) whereas nitrogen oxide is produced during both aerobic denitrification and as a result of chemodenitrification (2).
• Coffee contains antioxidants like chlorogenic acid and its isomers. In this report, effects of coffee on the nitrite-induced N2O3 formation were studied using whole saliva and bacterial fraction prepared from the saliva. The formation of N2O3 was measured by fluorescence increase due to the transformation of 4,5-diaminofluorescein to triazolfluorescein. Coffee inhibited the nitrite-induced fluorescence increase, and 50% inhibition was observed at several microg of coffee/mL in bacterial fraction of saliva as well as whole saliva. During the inhibition of the fluorescence increase, concentration of chlorogenic acid and its isomers decreased. It is discussed that the reduction of NO2 by chlorogenic acid and its isomers contributed to the coffee-dependent inhibition of the fluorescence increase as N2O3 is formed from NO and NO2. When coffee was added to whole saliva, chlorogenic acid and its isomers bound to cells in the saliva. The rate of the fluorescence increase in bacterial fraction, which was prepared at defined periods after the ingestion of coffee, was increased to the rate before the ingestion of coffee with a half-time of about 1 h. This result suggests that chlorogenic acid and its isomers remained in the oral cavity for a few hours after ingestion of coffee. The significance of coffee drinking and rinsing of the mouth with coffee for the health of the oral cavity is proposed (3).

Chemical safety 

• Molecular Formula  N₂O₃
• Molecular Weight   76.011 g/mol
• CAS   10544-73-7
• UNII   16E0524PXI
• EC number   234-128-5

Synonyms :

• Dinitrogen trioxide
• Nitrogen trioxide
• Nitrogen oxide (N2O3)
• nitrogen sesquioxide
• Nitrous anhydride
• N-oxonitramide
• EINECS 234-128-5
• trioxido-1kappa(2)O,2kappaO-dinitrogen(N--N)

References______________________________________________________________________

(1) Hopmann KH, Cardey B, Gladwin MT, Kim-Shapiro DB, Ghosh A. Hemoglobin as a nitrite anhydrase: Modeling methemoglobin-mediated N2O3 formation.    Chem - A Eur J. 2011;17:6348–6358. doi: 10.1002/chem.201003578. 

(2) Takahama U, Ryu K, Hirota S. Chlorogenic acid in coffee can prevent the formation of dinitrogen trioxide by scavenging nitrogen dioxide generated in the human oral cavity.   J Agric Food Chem. 2007 Oct 31;55(22):9251-8. Epub 2007 Oct 9.

(3) Colliver BB, Stephenson T. Production of nitrogen oxide and dinitrogen oxide by autotrophic nitrifiers.   Biotechnol Adv. 2000 May;18(3):219-32.