Nitrogen halides and related compounds

It is a curious paradox that NH3, the most stable binary halide of N, was not prepared until 1928, more than 115 y after the highly un.stable 

NF3 was first prepared by Otto Ruffs group in Germany by the electrolysis of molten NH4F/HF and this process is still used commercially. An alternative is the controlled fluorination of NH3 over a Cu metal catalyst. 

NF3 is a colourless, odourless, thermodynamically stable gas (mp —206.8°, bp —129.0°, AG29g — 83.3kJmol ). The molecule is pyramidal with an F-N-F angle of 102.5°, but the dipole moment (0.234 D) is only one-sixth of that of NH3 (1.47 D) presumably because the N-F bond moments act in the opposite direction to that of the lone-pair moment  

The gas is remarkably unreactive (like CF4) being unaffected by water or dilute aqueous acid or alkali at elevated temperatures it acts as a fluorinating agent and with Cu, As, Sb or Bi in a flow reactor it yields N2F4 (2NF3 - -2Cu N2F4 -I- 2CuF). As perhaps expected (p. 198) NF3 shows little tendency to act as a 

Dinitrogen tetrafluoride, N2F4, is the fluorine analogue of hydrazine and exists in both the staggered (trans) C2h and gauche C2 conformations 

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In 1967, Sanderson published a textbook with a unique chart of the elements, and related charts for hydrogen, nitrogen, oxygen, sulfur, halide, methyl, ethyl, and phenyl compounds. Shchukarev (1970,1974) published scores of elaborate graphs for classes of molecules (such as oxides of nitrogen) showing how values of molecular properties... 

Calculations of electron density and bond orders for compounds (28)-(30) have been performed using the SCF-LCAO-MO method, and this data has been reported <83AHC(34)80>. Studies after this have been directed at determining the sites of alkylation of (28) using semiempirical and ab initio calculations. The underlying assumption was that SNj attack on the halide was related to the electron density at the nitrogen atoms, the most appropriate measure of nucleophilicity would be the electron density in the HOMO which is of cr-symmetry. Ab initio calculations were in accord with the semi-empirical calculations and confirm alkylation at N-2. For systems (29) and (30), both methods of calculation confirm alkylation at N-3 <93T4307>. There is little data on theoretical chemistry associated with systems (17)-(27). 

Identification of Alkyl Halides.—On account of their relative inertness at ordinary temperatures the alkyl halides are usually identified by the determination of their physical properties. They are insoluble in concentrated sulphuric acid, and, unlike the acyl halides, they do not react readily with water and alcohols. Unlike the compounds in which halogen is joined to nitrogen, they are not easily changed by an aqueous solution of sodium hydroxide. They are distinguished from many halogen derivatives of benzene and related hydrocarbons, which will be described later, by the fact that they are decomposed when boiled with an alcoholic solution of potassium hydroxide —... 

Depending upon the basicity of the nitrogens, either haloformamidines or their hydrohalides are formed in the general synthetic procedures. The haloformamidines are in this, and in many other respects, quite closely related to the imidoyl halides (see Chapter 3). While the chloro and bromo compounds have a tendency to form the corresponding hydrohalides, the fluoro compounds, as usual, are nonpolar in character. 

We completed acute bioassays with Daphnia pulex for 35 representative and related chemicals from the following top-ranked classes for which available toxicity data were deemed inadequate to evaluate the hazard of the classes (National Fisheries Center - Great Lakes 1986 Perry 1985) polyaromatic hydrocarbons (PAHs), alkyl halides, mono- and polycyclic alkanes, heterocyclic nitrogen compounds, other nitrogen-containing compounds, and silicon-containing compounds (alkylether silanes). The acute bioassays with Daphnia pulex followed the methods of National Fisheries Center - Great Lakes (1986) with the temperature at 20° C. 

The activation energy of substitution of an unactivated aromatic halide (e.g., fiuorobenzene and 2-chloronaphthalene ) is over 30 kcal while that of activated compounds is 5-20 kcal. For the tabulated reactions (Tables II-VIII) with alkoxide and with primary, secondary, or tertiary amines, resonance activation (cf. 278 and 279) by ortho or para nitrogens is found to be greater than inductive activation (cf. 251). This relation is qualitatively demonstrated in... 

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