Structure, and kinetics of the thermal decomposition of organic phosphite ozonides

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Department of Chemistry; Department of Chemical Engineering


Activation parameters for uncatalyzed loss of oxygen from phosphite ozonide solutions (R alkyl or aryl) (RO)3P + O3 → (RO)3PO3 → (RO)3PO + O2 were measured for a number of different phosphites in several solvents. Triphenyl phosphite ozonide in toluene, chlorobenzene and acetonitrile showed Ea (kcal mol-1) = 19.4 - 20.1 and log A = 13.5 - 13.6, where A is in reciprocal seconds, whereas in dichloromethane the rate constants were not very reproducible and depended on the precautions followed to exclude moisture from the ozonide preparations. Activation parameters for triphenyl phosphite ozonide in dichloromethane reported in the literature or derived from reported rate constants vary from log A = 8.1 to log A = 11.9 and from Ea (kcal mol-1) = 14.4 to Ea = 17.2. Other phosphite ozonides show activation parameters which range approximately between the extremes given above for triphenyl phosphite ozonide, even in solvents other than dichloromethane. Possible reasons for these differences are discussed together with earlier theories to account for them. A molecular weight determination and the 31P nuclear magnetic resonance spectrum of trimethylolpropane phosphite ozonide are consistent with a monomeric non-equilibrating structure.

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Journal of Photochemistry