Nitrogen chemistry

The discovery in 1973 that polysulfur nitride (SN)X, a polymer comprised only of non-metallic elements, behaves as a superconductor at 0.26 K sparked widespread interest in sulfur-nitrogen (S-N) chemistry. In the past 30 years, the field of inorganic S-N chemistry has reached maturity and interfaces with other areas of chemistry, e.g., theoretical chemistry, materials chemistry, organic synthesis, polymer chemistry and biochemistry, have been established and are under active development. This interest has been extended to Se-N and, to a lesser extent, Te-N systems. 

S-nitrosothiols (RSNO) have emerged as important species in the storage and transport of nitric oxide. As NO donors these S-N compounds have potential medical applications in the treatment of blood circulation problems. 

Although progress in the chemistry of Se-N and Te-N compounds has been slower, there have been impressive developments in the last 10 years. Significant differences are apparent in the structures, reactivities and properties of these heavier chalcogen derivatives, especially in the case of tellurium. In addition, the lability of Se-N and Te-N bonds has led to applications of reagents containing these reactive functionalities in organic synthesis and, as a source 

A book on chalcogen-nitrogen chemistry has been published recently.1 Reviews on specific aspects of chalcogen-nitrogen chemistry that have appeared in the last 10 years are listed in reverse chronological order in refs. 2-18. 

Some of the fundamental properties of sulfur, selenium and tellurium differ significantly from those of oxygen, giving rise to disparities between the structures and properties of heavier chalcogen-nitrogen molecules and ions compared to those of their N-O counterparts. The major contributors to these differences include the following  

Emissions of nitrogen oxides and sulfur oxides from combustion systems constitute important environmental concerns. Sulfur oxides (SO ), formed from fuel-bound sulfur during oxidation, are largely unaffected by combustion reaction conditions, and need to be controlled by secondary measures. In contrast, nitrogen oxides (NO ) may be controlled by modification of the combustion process, and this fact has been an important incentive to study nitrogen chemistry. Below we briefly discuss the important mechanisms for NO formation and destruction. A more thorough treatment of nitrogen chemistry can be found in the literature (e.g., Refs. [39,138,149,274]). 

Five separate mechanisms have been identified that can lead to formation of nitrogen oxides in significant quantities. Four of these mechanisms are initiated by fixation of the molecular nitrogen contained in the combustion air. For fuels such as coal or biomass that contain nonnegligible amounts of fuel-bound nitrogen, so-called fuel-NO constitutes an additional formation route. 

Most gaseous fuels as well as some liquid fuels contain no or only small amounts of chemically bound nitrogen. In combustion of these fuels, the important source of NO is fixation of N2 in the combustion air. Molecular nitrogen, with its triple bond, is very stable, and only very reactive radicals may succesfully attack N2. The mechanisms of NO formation from N2 is quite well understood [274], and for many applications semiquantitative predictions of NO are within reach. 

1 Thermal NO Formation Of the four mechanisms that involve fixation of N2 from the combustion in air, the thermal NO mechanism, is the most significant. It is also 

2 Prompt NO Formation A second source of NO in gas firing is prompt NO. This formation pathway can be the dominating source of NO under conditions characterized by lower temperatures, fuel-rich conditions, and short residence times. This route, which is also called Fenimore NO, was first proposed by C. P. Fenimore [125]. Prompt NO formation is initiated by attack of CH, radicals on N2, forming cyanide species. The most important initiation step is the reaction 

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T. Chivers, Selenium-Nitrogen Chemistry, Main Group Chemistry News, 1, 6 (1993). 

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