Nitrosyl bromide, reaction

Nitrosyl bromide (NOBr) decomposes to nitrogen oxide and bromine. Use the following data to determine the order of the decomposition reaction of nitrosyl bromide. 

Formed as an intermediate in the Pb chamber process for sulfuric acid by the reaction of sulfur dioxide, nitrogen trioxide, oxygen and w (chamber crystals) (Refs 1 2). Can be prepd from Ag acid sulfate and nitrosyl bromide (Ref 4)... 

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. 

The change produced by nitrosyl bromide was found to be optically abnormal the following reactions occurred —... 

It may be concluded that the Walden inversion is limited to the reactions between nitrosyl bromide and the amino group and between silver oxide and halogen fatty acid, and is dependent upon the presence of the carboxyl group. 

Reactions with chlorine and bromine form nitrosyl chloride and nitrosyl bromide, respectively ... 

Another method of preparation involves the reaction of nitrosyl bromide with silver bisulfate ... 

In a study of the addition of nitrosyl chloride or nitrosyl bromide to norbor-nene and norbomadiene, it was observed that (a) there was no structural rearrangement during the reaction, (b) a cis addition had taken place, (c) nucleophilic solvents such as ethanol or acetic acid were not incorporated in the products. These facts seem to speak against an ionic addition mechanism, while a free radical initiated by NO radicals was considered unlikely since nitric oxide is inactive toward norbomadiene. Therefore a four-center mechanism has been suggested [70], However, when a relatively simple, unstrained olefin such as A9-octalin was subjected to the reaction, only blue, crystalline, monomeric 9-nitroso-10-chlorodecalin was produced. This product had a trans configuration. Thus it is evident that the structure of the olefin has a significant bearing on the steric course of the addition [71]. 

On the other hand, nitrosyl bromide is ineffective. This may be attributed to the fact that the reagent is extensively dissociated to afford nitric oxide and molecular bromine. Furthermore, in the case of some amides, reaction with nitrosyl bromide results in the formation of complex crystalline compounds containing reactive bromine. 

The reaction of nitric oxide with bromine to form nitrosyl bromide has not been so thoroughly investigated. 

The gas-phase reaction of nitric oxide and bromine yields nitrosyl bromide ... 

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... 

If nitrosyl bromide is allowed to react with hydrated rhodium trichloride and PPh3 in ethanol, the mixed chlorobromo complex is obtained (equation 301).13 3 When [RhCl(PPh3)3] is the substrate the dibromo complex is formed (equation 302). This complex can also be obtained from rhodium tribromide, JV-methyl-JV-nitrosotoluene-p-sulfonamide and PPh3. Replacement of PPh3 by other tertiary phosphines permits analogous dibromo complexes to be prepared (cf. equation 299). Another source of the triphenylphosphine complex is [Rh(NO)2Br] . The diiodo complex can be obtained from a similar reaction mixture containing Lil (equation 304).1293... 

Among examples studied are the nitrosation of hydroxylamine and its methyl derivatives (M. N. Hughes et al., 1968), hydrazine (Perrott et al., 1976) and the methylhydrazines (Perrott et al., 1977). In all cases reaction occurred via the conjugate acid of the substrate, and although thiocyanate ion catalysis is more pronounced than that of bromide ion, the second order rate constants for reaction (25) were found to be approximately 100 times less than for nitrosyl bromide. More recent work with both morpholine and aniline showed the... 

A sample of gaseous nitrosyl bromide, NOBr, was placed in a rigid flask, where it decomposed at 25°C according to the following reaction ... 

Nitrosyl chloride can be obtained by direct combination of chlorine with nitric oxide, by the reaction of NOHSO4 or NaNOj with HCl, or as a by-product in the preparation of KNOs from KCl and NO2, in which KCl is moistened with 2.4% water. Nitrosyl bromide is usually prepared by direct combination of bromine nuth nitric oxide. Nitrosyl chloride and nitrosyl bromide can be prepared by reacting the appropriate potassium halide with nitrogen dioxide at room temperature. The reaction rate increases with increased size of the halide, and NOCl and NOBr can be obtained in a reasonable length of time by powdering the halide salt before adding NO. ... 

Storage of nitrosyl fluoride in the glass reaction vessel containing KF is possible for a few days however, the use of an inert-metal vessel containing anhydrous KF is preferred for an extended period of time. Nitrosyl chloride is stable at room temperatxure but will always contain a small amount of NO and CU because of its reversible decomposition of 0.5%. The reversible decomposition of nitrosyl bromide is appreciable enough at room temperature (7 %) to require storage at a lower temperature, or the gas can be prepared immediately prior to use. ... 

Potassium bromide is prepared in the same manner as described for KCl. The addition of 0.002 mole of NOa to the reaction vessel allows essentially complete reaction to occxur within 30 minutes. The yield is generally greater than 90%. The product obtained is a red-colored gas similar in appearance to NOa. Nitrosyl bromide undergoes reversible decomposition at room temperature to the extent of about 7 %. The presence of the excess KBr does not appear to affect this equilibrium. 

On the other hand, Lison (1951), without giving his procedures in any detail, has reported failure to obtain a detectable reaction in droplets by a Piloty reaction (color reaction of ketones with nitrosyl bromide). 

Scheme 10.26. A portion of the scheme (1895) of the original Walden inversion sequence of reactions. This part involves treatment of (5 )-(+)-2-aminosuccinic acid (aspartic acid) with NOBr (nitrosyl bromide) to produce (5 )-(-)-2-bromosuccinic acid and presumably involves formation of a diazonium ion, an a- or 3-lactone, and opening of the latter (with overall retention) by bromide anion. Given the bond angles involved, the 3-lactone is considered more likely. See Clough, G. W. /. Chem. Soc. Trans., 1918,113,526.

Nitrosyl halides, at least in aqueous solutions, appear to be more potent reagents than nitrous anhydride. Schmid and his coworkers have calculated actual rate coefficients for the reaction of unprotonated amine with both molecular nitrosyl chloride and nitrosyl bromide (i.e. from the equation. Rate = A[RNH2][NOHal]). These are listed in Table 6. The characteristic features of these rate... 

At 77°C, 2.00 mol of nitrosyl bromide, NOBr, placed in a 1.00-L flask dissociates to the extent of 9.4% that is, for each mole of NOBr before reaction, (1.000 0.094) mol NOBr remains after dissociation. Calculate the value of for the dissociation reaction... 

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