CIO”, reaction with

The rate constant for paths a and b have been determined to be /q,u = 5.3 X 10-I2 i-2II// and k(llb = 1.1 X 10 l4e m/1 cm3 molecule-1 s-1, respectively (Harwood et al., 1998). At temperatures below 250 K, the termolecular reaction forming the dimer becomes relatively more important (Harwood et al., 1998). However, this self-reaction is not important because of the relatively small concentrations of BrO in the stratosphere. Reactions with CIO and HOz are much more important. 

Note that the O atom concentration in the lower stratosphere is too low for its reaction with CIO to compete effectively with the CIO + N02 reaction.)... 

A second order reaction is conducted in two equal CSTR stages. The residence time per stage is T = 1 and the specific rate is /cCq = 0.5. Feed concentration is Cq. Two cases are to be examined (1) with pure solvent initially in the tanks and (2) with concentrations Cq initially in both tanks, that is, with Cio = Coq = Cq. 

P(OR)3, Sb(III), or Sn(II) is also extremely slow, so slow that complications attributable to the reaction of CIO with these... 

S(IV) with BrO is 24.5 kcal mol 1 more exothermic than that with CIO. It is reasonable to suppose that the reaction coordinates for the two reactions are similar. If it is assumed then that half of the difference in driving force is reflected... 

The reaction of CIO- with methyl chloride can only proceed via the Sn2 process. An inverse KIE of 0.85 is measured (Table 10.3). The reaction with /-butyl chloride presumably proceeds via an E2 mechanism (since Sn2 attack on the Cl substituted carbon is blocked) and the observed KIE of 2.31 (Table 10.3) is consistent with that conclusion. The isotope effects for both species are nearly the same as the effects measured in the condensed phase (compare Tables 10.3 and 10.4) and measure the relative contributions of the two paths. The results indicate that the E2 pathway becomes the dominant channel as the substrate becomes more sterically hindered. 

Linear alkylbenzenes are made from -paraffms (Cio-Cu) by either partial dehydrogenation to olefins and addition to benzene with HF as catalyst (60%) or chlorination of the paraffins and Friedel-Crafts reaction with benzene and an aluminum chloride catalyst (40%). See Chapter 24 for more information. 

CI2 + 60H- 5C1- CIOs + 2H2O Reaction with lime produces a calcium salt, known as bleaching powder ... 

Reaction with chlorine yields chlorine monoxide, CIO, and in aqueous solution or with chlorine water, the product is hypochlorous acid, HOCl ... 

Chlorine nitrate is formed from the reaction of CIO with N02.) These reactions also occur when NaCl is in the aqueous phase, in competition with the hydrolysis of N205 and C10N02, i.e., above the deliquescence point of NaCl in sea salt (e.g., Behnke et al., 1997). Photolysis then generates chlorine atoms, e.g.,... 

However, with the recent recognition of the potential importance of atomic chlorine and bromine under certain conditions in the Arctic at polar sunrise (e.g., see Barrie et al., 1988 and Niki and Becker, 1993), the potential for BrO and CIO chemistry has been reconsidered. As described in Chapter 6 J.4, at polar sunrise there is a rapid loss of ground-level 03 that appears to be associated with reaction with atomic bromine and at the same time, there is evidence that chlorine atoms are playing a major role in the organic removal (Jobson et al., 1994). This is consistent with reactions of sea salt particles generating atomic bromine and chlorine, although the exact nature of the reactions and halogen atom precursors remains unknown. 

The CIO + DMS reaction is quite slow, with a rate constant at 298 K of only 9.5 X 10 15 cm3 molecule s-1 (Barnes et al., 1991). Combined with the fact that Cl reacts with organics at essentially a diffusion-con-trolled rate, while the rate constant for reaction with 03 is about an order of magnitude slower, the CIO + DMS reaction is not expected to be important in the troposphere. 

This reduces the H02 concentration, and hence its contribution to 03 destruction via reaction (8) of HOz with 03. In addition, the rates of reaction of FI02 with CIO and BrO decrease with less HOz, which lowers the rate of 03 destruction through cycles outlined later. 

This cycle accounts for 30% of the ozone loss due to halogens in the lower stratosphere, and the corresponding cycle for bromine for 20-30% (Wennberg et al., 1994). Reaction of CIO with HOz, reaction (28), produces HOC1 + 02 with a yield >95% at temperatures from 210 to 300 K however, at the lowest end of this temperature range, there is evidence for the produc-... 

---