Matrix effects in the low-temperature ozonation of ethylene, tetramethylethylene and 1-hexene

The ozonation of the title compounds was studied in argon and CO2 matrices at low temperatures (12-80 K). All three were found to react with ozone in a CO2 matrix deposited at low temperature, and having an amorphous structure. The reaction was found to start at 26 K, the temperature at which the matrix undergoes a phase transition. In contrast, only tetramethylethylene (TME) was found to react in an argon matrix, the other two compounds remaining inactive towards ozone up to the softening temperature of argon (similar to 40 K). These results are interpreted as indicating that reaction between olefins and ozone is initiated at low temperatures once the two reactants are free to move to the required configuration. This idea is supported by molecular dynamics simulations on the TME reaction. The infrared spectra of the primary ozonide of TME, as well as of the primary and secondary ozonide of l-hexene are reported, and compared with quantum chemical calculations. (C) 1998 Elsevier Science B.V.