N- compounds

Among all usual parameters for water quality control, nitrogen is probably the most known and monitored, particularly nitrate. N is present in water in reduced form (organic and ammonium nitrogen) and oxidised form (nitrites and nitrates). The evolution of the N compounds depends on physico-chemical and biological mechanisms occurring in natural water or all along treatment processes (Fig. 2). 

A simple methodology, called UV/UV method, has been designed for the quick determination of the different forms of nitrogen in water, nitrite, nitrate, ammonium and TKN [4]. The general procedure is based on several steps (Fig. 3) but includes a UV determination of the oxidised forms and one or two UV photo-oxidation step(s) for the mineralisation of the reduced forms. Neither filtration nor acidification of the sample is needed. 

In the third part of the general procedure (way C), the sample is photo-oxidised in the presence of an acidic oxidant solution (pH 2 with sulphuric acid 20%). In these conditions, only organic nitrogen is converted into nitrate. The difference between the concentration of TKN previously calculated and that of organic nitrogen leads to the calculation of ammonium nitrogen concentration. 

all nitrogen forms (N0x, N0rg, NH, TKN) can be rapidly and simply determined. 

Several dozens of works have been published for more than 50 years on the subject, and a few of them are cited hereafter. The proposed methods can be classified according to the exploitation method used, among those presented in Chapter 2  

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Boron forms B—N compounds that are isoelectronic with graphite (see Boron compounds, refractoryboron compounds). The small size also has a significant role in the interstitial alloy-type metal borides boron forms. Boron forms borides with metals that are less electronegative than itself including titanium, zirconium, and hafnium. 

When hexafluoroacetone-0-tosyloxime reacts with pnmary amines acting as 1,1 [n,n] compounds, 3,3-his(trifluoromethyl)diaziridines are obtained [100] with O-alkylhydroxylamines, the corresponding diazitine is formed [101] (equation 21)... 

Three skeleton atoms of a hetero-l,3-diene are incorporated into a five-membered ring system on reaction with 1,2 [n,n] compounds (e.g., hydrazines, reaction type 4, equation 10). On further heating in the presence of azobisiso-butyronitrile (AIBN), the bis(trifluoromethyl)-substituted 1,2,4-triazolines are transformed into 5-tnfluoromethyl-l,2,4-triazoles in high yield [t02 (equation 22). 

Six-membered rings also result from the reaction of 1,3-diazabutadienes with 1,3 [n,n] compounds such as amidines and certain cyclic 1,3-diketones [97]... 

A. Haas, Acyclic and Heterocyclic Te-S-N Compounds A Review of Recent Publications, J. Organomet. Chem., 646, 80 (2002). 

N,N - Bis(trimethylsilyl)sulfur(rV) diimide Me3SiN=S=NSiMc3 is an especially versatile source of the N=S=N functionality in the formation of both acyclic and cyclic S-N compounds. It is conveniently prepared by the reaction of NaN(SiMc3)2 and thionyl chloride (Eq. 2.5). 

In S-N compounds containing H bonded directly to nitrogen, inverse detection 2D NMR spectroscopy can be applied to give N... 

The only sulfur isotope with a nuclear spin is which is quadrupolar (/ = 3/2) and of low natural abundance (0.76%). In view of these inherent difficulties and the low symmetry around the sulfur nuclei in most S-N compounds, S NMR spectroscopy has found very limited application in S-N chemistry. However, it is likely that reasonably narrow resonances could be obtained for sulfur in a tetrahedral environment, e.g. [S(N Bu)4], cf. [S04] . On the other hand both selenium and tellurium have isotopes with I = Vi with significant natural abundances ( Se, 7.6% and Te, 7.0%). Consequently, NMR studies using these nuclei can provide useful information for Se-N and Te-N systems. 

The Se NMR chemical shifts of Se-N compounds cover a range of >1500 ppm and the value of the shift is characteristic of the local environment of the selenium atom. As a result, Se NMR spectra can be used to analyse the composition of a complex mixture of Se-N compounds. For example, Se NMR provides a convenient probe for analyzing the decomposition of selenium(IV) diimides RN=Se=NR e.g., R = Bu). By this method it was shown that the major decomposition products are the six-membered ring (SeN Bujs, the five-membered ring Sc3(N Bu)2 and fifteen-membered ring Sc9(N Bu)6 (Figure 3.2 and Section 6.3). 

Paradoxically, although they are electron-rich, S-N compounds are good electron acceptors because the lowest unoccupied molecular orbitals (LUMOs) are low-lying relative to those in the analogous carbon systems. For example, the ten r-electron [SsNs] anion undergoes a two-electron electrochemical reduction to form the trianion [SsNs] whereas benzene, the aromatic hydrocarbon analogue of [SsNs], forms the monoanion radical [CeHg] upon reduction. ... 

Low ionizing potentials or soft ionization methods are necessary to observe the parent ions in the mass spectra of many S-N compounds because of their facile thermal decomposition. Mass spectrometry has been used to investigate the thermal breakdown of S4N4 in connection with the formation of the polymer (SN). On the basis of the appearance potentials of various S Ny fragments, two important steps were identified ... 

In order to understand the physical properties and reactivity patterns of S-N compounds it is particularly instructive to compare their electronic structures with those of the analogous organic systems.On a qualitative level, the simplest comparison is that between the hypothetical HSNH radical and the ethylene molecule each of these units can be considered as the building blocks from which conjugated -S=N- or -CH=CH-systems can be constructed. To a first approximation the (j-framework of... 

A variety of acyclic and cyclic S-N compounds decompose at moderate temperatures (100-150°C) with the formal loss of a symmetrical NSN fragment, but this molecule has never been detected. The lowest energy isomer, linear NNS, is generated by flash vacuum pyrolysis of 5-phenyl-1,2,3,4-thiatriazole (Eq. 5.1). ... 

In spite of the hazardous nature of Sc4N4, this binary selenium nitride has been used for the synthesis of other Se-N compounds, all of which have sulfur analogues (Scheme 5.2). " However, safer alternatives to the use of Sc4N4, e.g., selenium-nitrogen halides and silicon-nitrogen-selenium reagents, are available for the development of Se-N chemistry. ... 

The thiazyl cation is used for the preparation of other important S-N compounds (Scheme 5.3). For example, the insertion reactions with S4N4... 

Phosphorus by Heal covered developments up to the end of the 1970s. This opus contributed authoritative insights into the fascinating chemistry of S-N compounds. It used a descriptive approach that drew attention to the many facets of the synthesis, structures and reactions that were poorly understood at that time. 

Two factors have contributed to the special interest that attaches to B-N compounds. First, the B-N unit is isoelectronic with C-C and secondly, the size and electronegativity of the 3 atoms are similar, C being the mean of B and N ... 

The cyclic borazine (-BH-NH-)3 and its derivatives form one of the largest classes of B-N compounds. The parent compound, also known as inorganic benzene , was first isolated as a colourless liquid from the mixture of products obtained by reacting B2H6 and NH3 (A. Stock and E. Pohland, 1926) ... 

This section deals with the binary compounds that nitrogen forms with metals, and then describes the extensive chemistry of the hydrides, halides, pseudohalides, oxides and oxoacids of the element. The chemistry of P-N compounds is deferred until Chapter 12 (p. 531) and S-N... 

The study of 8-N compounds is one of the most active areas of current inorganic research many novel cyclic and acyclic compounds are being prepared which have unusual stmctures and which pose considerable problems in terms of simple bonding theory. The discoveiy in 1975 that the polymer (8N)jc is a metal whose conductivity increases with decrease in... 

It will be convenient to describe first the binary. sulfur nitrides SjN,. and then the related cationic and anionic species, S,Nv. The sulfur imides and other cyclic S-N compounds will then be discus.sed and this will be followed by sections on S-N-halogen and S-N-O compounds. Several compounds which feature i.solated S<—N, S-N, S = N and S=N bonds have already been mentioned in the. section on SF4 e.g. F4S NC,H, F5S-NF2. F2S = NCF3, and FiS=N (p. 687). Flowever. many SN compounds do not lend themselves to simple bond diagrams, - and formal oxidation states are often unhelpful or even misleading. 

The cation has considerable synthetic potential for a wide range of S/N compounds,... 

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