BrO radical

Br-atom initiated oxidation of dimethyl sulfide (DMS) in a large-volume reaction chamber gave SO2, CHsSBr, and DMSOJ A rapid addition of Br atoms to DMS takes place, forming an adduct that mainly reforms reactants but also decomposes unimolecularly to form CHsSBr and CH3 radicals. DMSO is formed from the reaction of BrO radicals with DMS. The reaction CH3O2 + Br CH3O + BrO is postulated as the source of BrO radicals. 

CF2Cl)2CO and CFC]2C0CF2C1 and in the electrical discharge103 of fluorocarbons. In the presence of a large excess of 02 there was no evidence for BrO radicals in contrast to analogous experiments with CCl2Br2. Furthermore, the CF2 concentration was independent of the 02 pressure. Simons and Yarwood concluded that the primary process was... 

A second catalytic cycle involves the CIO and BrO radicals, which react some form Cl and Br atoms, which can then react with ozone to form CIO and BrO again. 

Atmospheric Reaction Mechanism. In the atmosphere the reaction subsequent to OH radical attack have not been unambiguously determined. It Is presumed that the radicals formed will Initially react with O2 and ultimately produce Cl or Br atoms or CIO or BrO radicals. The photolysis of CFCI3 and CF2CI2 under laboratory conditions leads ultlMtely to the formation of COFCl and C0F , respectively (180, 181) ... 

The method of molecular absorption has been used for Br atoms in the author s laboratory to check the stoichiometry of the titration reaction, Br + CINO -> BrCl + NO. It has also been used to measure the kinetics of radiative and nonradiative third-order recombination of Br atoms, and to follow [Br] in the bimolecular disproportionation of two BrO radicals these were shown to decay by the reaction BrO -f BrO -> 2Br -f- O2. It appears that vibrational relaxation of Bra, which might affect the method, was complete under the conditions used. One advantage of the molecular absorption method is its relative instrumental simplicity. However, the method is clearly inapplicable to any system in which interfering absorption by transients, reactants or products can occur. 

A two-pinhole, unmodulated beam inlet system has been used by Clyne and Watson to detect the hitherto unknown gaseous FO radical (from F -H Os -> FO -1- O2), and the CIO and BrO radicals, and to measure the rates of a number of elementary reactions involving CIO and BrO radicals, such as. 

The decay reaction of BrO radicals was also found to be second-order, but was much more rapid than that of CIO radicals at 300 K. ... 

The system shown in Figure 13 is an improved version of that described by Clyne and Watson. The new vereion was designed by I. S. McDermid in our laboratoiy. The loww limits of detection of CIO and BrO radical concentrations with Qyne and Watson s system were [OO] > 1 x 10 cm and [BrO] > 1.5 X 10 cm" ... 

The relatively complicated case of CIO + CIO, where two closely related reactive channels (47a) and (47b) are identified, cannot be paralleled for BrO -I- BrO. No stable OBrO molecule (analogous to OCIO) is definitely known, nor has gaseous BrOO ever been detected as a transient or otherwise. Therefore, the dissociation energy of BrOO, if it exists, must be considerably less than the 29kJmol" suggested for CIOO. In the work of Oyne and Cruse, the number of bromine atoms found from reaction of BrO + BrO approached the number of BrO radicals consumed. This result confirms the correctness of writing this reaction as BrO + BrO -> 2Br + O2 and also confirms a lack of stability for the BrOO radical which, by analogy with CIO -I- QO, is likely to be the initial product, with Br, of reaction (49). In this case, the most probable fate of BrOO... 

---