Nitrosyl halides, reaction

Such reactions provide an excellent route to anhydrous metal nitrates, particularly when metal bromides or iodides are used, since then the nitrosyl halide decomposes and this prevents the possible... 

The stable molecular nitrosyl halides NOX (p. 442) and phosphoryl halides POX3 (p. 501) find few counterparts in the chemistry of As, Sb and Bi. AsOF has been reported as a product of the reaction of AS4O6 with ASF3 in a sealed tube at 320° but has not been fully characterized. ASOF3 is known only as a polymer. Again, just as AsClj eluded preparation for over 140 y after Liebig s first attempt to make it in 1834, so... 

Schmid s observation of the dependence of the reaction rate on the square of the concentration of nitrous acid was interpreted by Hammett (1940, p. 294) as due to the rate-limiting formation of dinitrogen trioxide, N203. The consequent attack of the amine by N203 was postulated to be faster therefore the concentration of the amine has no influence on the overall rate (zero order with respect to amine). Similarly, Hammett regards the second factor of Schmid s equation for diazotization in the presence of hydrochloric or hydrobromic acid as the result of the formation of nitrosyl halide. 

A number of gaseous oxyhalides of nitrogen are known, including the types XNO (nitrosonium or nitrosyl halides) with X = F, Cl, or Br, and XN02 (nitryl halides) with X = F or Cl. Nitrosonium halides are prepared by the reactions of halogens and NO. 

Our latest results in this field stem from a matrix-spectroscopic study of the isomerization of nitrosyl halides (152) and isonitrosyl halides (153).201 Irradiation of nitrosyl bromide (152 X = Br) and nitrosyl chloride (152 X = Cl) leads to the corresponding isomers isonitrosyl bromide (153 X = Br) and isonitrosyl chloride (153 X = Cl). Both compounds, NOBr and NOC1,202 have again been identified by comparison of the experimental and calculated (BLYP/6-311+G ) IR spectra. The back-reactions 153 - 152 can be initiated by UV, visible or IR light. Astonishingly, this retransformation also occurs spontaneously even in the matrix at 10 K under exclusion of any UV/VIS or IR radiation. 

There are numerous examples of the demonstration of the catalytic activity of thiocyanate ion for a wide variety of substrates. In general the reaction of ONSCN is rate-limiting, but in some cases (just as for the nitrosyl halides) with very reactive substrates the formation of ONSCN can be rate-limiting. 

Nitrosyl Halides.26 The exothermic reactions of I(52Py2) with NOC1 and NOBr19,145... 

Somewhat analogous to the Reed process is a recent development in which an olefin is reacted with nitrosyl chloride to form a nitrosyl halide, which in turn is converted to a mixture of complex sulfonates by reaction with sodium sulfite (4). These materials are reported to be excellent metal cleaning detergents. 

Diazotization is a complex reaction (Scheme 1). When performed in acidic media with sodium nitrite, NOx or nitrosyl halides, its kinetics are dependent upon the acidity of the medium in media with a Hammett acidity constant (-H0) from — 1 to 3 the reaction rate increases with acidity and the formation of the nitroso cation is the rate-limiting step, in more acidic media (-H0 > 4) the reaction rate decreases when acidity increases and the deprotonation of intermediate 6 is the rate-limiting step.6-9... 

In a lecture presented to the Faraday Society,332 Norrish commented on why the higher vibrational levels of NO were observed in the nitrosyl halide experiments but not by absorption in NO irradiation experiments. He reasoned that, as the emission of NO from the AZH + state populates the first five vibrational levels of NO almost equally,341 the fast-exchange reaction (4) can quickly eliminate all the vibrational levels above the first. However, in the nitrosyl halide experiments, the NO may be formed preferentially in very high levels, such as v — 10 or 11, almost exclusively. Thus, reaction (4) cannot occur initially, and depopulation must be by reaction (2). Reaction (2) is considerably slower than reaction (4), because of the increased difference in vibrational energy between the reactants and products resulting from an-harmonic effects. 

Fig. 1. Diazotization of aromatic amines through the intermediate formation of nitrosyl halides (NOX). The variation of the rate coefficient k (eqn 16) with the pXa-value of the amine. The broken line indicates the expected limit for a diffusion-controlled reaction. +. .. X = Cl O X = Br...

Dichlorodinitrosylmolybdenum and tungsten have been prepared by the reaction of the appropriate hexacarbonyl with nitrosyl chloride in dichloromethane.1 The corresponding dibromo derivatives have been prepared by a similar reaction with nitrosyl bromide.2 These are the only synthetic routes to these compounds they are rapid (3 hours) and convenient. The corresponding chromium compounds are unknown. This method is a general route to transition-metal nitrosyl halide... 

Nitrosyl halides add to alkenes references are scattered through the litnnture back to 1875 (ref. 194 and references cited therein). The adducts vary enormously in their stability, but when their structures allow they, like nonhalogenated nitroso compounds, isomerize to oximes or dimnize. The orientation of the reaction is consistent with an electrophilic medumism, in which the reagent is polarized as NO Hat. Bicyclic substrates and reaction media of low polarity favor syn addition, suggesting a four-center transition state (Scheme 81). Aziridine synthesis via NOCl/alkene adducts is discussed in Section 3.5.2.1. 

N-Nitrosation of oximes by nitrosyl halides or nitrite esters often results in the formation of N-nitrimines, R R C=NN02, these compounds being formed by rearrangement of the initial adducts. N-Amination of oximes by chloramine or by hydroxylamine-O-sulfonic acid can result in the formation of diazo compounds (Scheme 28). The reaction, known as the Forster reaction, has been used for the preparation of aryldiazoalkanes, although better methods are usually available. Diazo ketones of the general formula (49) have also been prepared by this method from the oximes. "... 

The uncertainty of the equilibrium constant for N2O3 formation highlights the general problem of calculating true rate constants for processes which involve pre-equilibria. The equilibrium constants must be reliably known if the rate constants are to be meaningful. The same argument applies of course to nitrosyl halide and other reactions. It must also be established whether reaction occurs only via the free base form of the amine and again the p/ka-value must be known with certainty. 

Nitric oxide forms nitrosyl halides in the reaction with chlorine and bromine (see Section 9.1) in the reaction with fluorine, both nitrosyl fluoride and trifluoramine oxide are formed (see Section 9.3). 

Nitrosyl halides can be obtained by the direct reaction of the respective hahdes with nitrogen monoxide at slightly elevated temperatures (310-320 K). 

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