HOCO radical reaction with

Reaction (11), which may also proceed via collisional stabilisation to a HOCO radical has been the subject of numerous kinetic and dynamics studies over the past 30 years. At room temperature its rate constant is k29g = 1.5 x 10 cm molecule s but below 500 K the activation energy is almost zero. Recent measurements [11(b)] show that the rate constant only falls slightly as the temperature declines to 80 K. Unfortunately, the reaction is too slow to measure at lower temperatures in the present generation of CRESU experiments. The linear flow is so fast, that the first-order rate constant for decay of the radical concentration must be > 5 x 10 s with the result that any bimolecular reactions for which the rate constant is < 10 cm molecule s" cannot be successfully studied. 

Li, Q., M.C. Osborne, and l.W.M. Smith (2000a), Rate constants for the reactions of Cl atoms with HCOOH and with HOCO radicals, IrU. J. Chem. Kinet., 32, 85-91. 

An example of the application of transition state theory to atmospheric reactions is the reaction of OH with CO. As discussed earlier, this reaction is now believed to proceed by the formation of a radical adduct HOCO, which can decompose back to reactants or go on to form the products H + COz. For complex reactions such as this, transition state theory can be applied to the individual reaction steps, that is, to the steps shown in reaction (15). Figure 5.3 shows schematically the potential energy surface proposed for this reaction (Mozurkewich et al., 1984). The adduct HOCO, corresponding to a well on the potential energy surface, can either decompose back to reactants via the transition state shown as HOCO./ or form products via transition state HOCO,/. ... 

The p-halogenotetradecachlorotriphenylmethyl radicals. In the carbanion synthesis of the radical HOCO—PTM- from HOCO—PTM—H in the conventional manner, the radical I—PTM- is a minor by-product. It appears that the intermediate dianion OCO—PTM reacts rapidly with iodine, giving the radical OjC—PTM- (Ballester ct a/., 1982b Ibanez, 1972). High concentrations of iodine and/or long reaction times cause the formation of the radical I—PTM- as a major product by oxidative decarboxylation. It has been found that the dianion "O2C—PTM is stable under the reaction condition (Ballester et al., 1982b Ibanez, 1972). These results may be accounted for as shown in (142) through the intermediacy of acyclic,... 

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