| OCR Text |
Show Benzenethlol , phenol , and benzy l chloride all form resonance stabilized radicals following dissociation of relatively weak sulfurhydrogen , oxygen-hydrogen, and carbon-chlorine bonds. However, the low T99s for these compounds suggest that bimolecular reactions involving hydrogen abstraction may also be significant. The carbon-nitrogen bond in nitrobenzene is only 70 kcal/mole, suggesting a mechanism of simple bond homolysis. The fragile nature of pyridine (T99 = 620°C) and 1,4 dioxane (T99 = 660°) suggest concerted low energy pathways. Such pathways have been identified for sym-trioxane and it is known that pyrazines, triazines, and tetrazines are very fragile, decomposing in some cases, near room temperature. Methyl ethyl ketone is expected to decompose by radical abstrac-tion of a hydrogen atom. Although room temperature hydroxyl radical kinetic data suggest the rate is slowed by the carbonyl group versus the corresponding alkane, our data suggests the rate is increased at high temperature. (12] ~crylamide may decompose by H attack on the olefinic group or abstraction of the amine hydrogens. The latter may be increasingly important at high temperature. Both nitrile contain-ing compounds are all very stable with T99s of 980, and 880°C for acetonitrile and propionitrile respectively. The observed stability trend is consistent with the trend observed for hydroxyl radical ~ attack on these two molecules. (12] The stability of nitrile con-taining compounds is apparently due to the ability of the polar nitrile group to destabilize the electron deficient radical inter-mediate formed by radical attack. The series of chlorinated alkenes, hexachlorobutadiene, 1,2 dichloroethene, 1,1-dichloroethene, trichloroethene, and |
