Database for the primary initiation process

Although the data shown in Tables 1.7 and 1.8 are relatively limited and come from only one laboratory, (1) is a key reaction over a wide 

II Delocalized electron involving the loss of one rotation (e.g., alkenes, alkylbenzenes). 

The decreasing values of A from I to III are consistent with the extra loss of entropy of activation (ca 18JK moF per lost rotation) in the emerging electron-delocalized radicals. The data base is probably reliable to a factor of 2 between 600 and 1200 K unless there is a very marked non-Arrhenius behaviour in i. Below 600 K, (1) is far too slow to influence events and above 1200 K, reaction (lA) will dominate unless the O2 pressure is very high (ca 20 atms) (Table 1.11). 

Reaction (lA) is the other major primary initiation process, particularly above 1000 K. Kinetic data have been available for a number of years, partly because /cia is relatively easy to measure because secondary initiation is effectively absent. Nevertheless, the systems used are invariably complex and care is necessary in abstracting /cia- Tsang [47,48] has used a single-pulse shock-tube with considerable success by use of an approach whereby relative rate constants are obtained with one known accurately as a reference. Baldwin, Walker and Drewery [34] have shown that Eia can 

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