Environmental Effects on the Formation of the Primary and Secondary Ozonides of Ethylene at Cryogenic Temperatures

Ethylene and ozone were co-deposited in a cryogenic matrix of argon at 15−26 K and of CO 2 at 12−20 K. In the argon matrix, no perceptible reaction took place at any temperature below the softening onset of the matrix, while formation of ethylene ozonides (both primary and secondary) was observed at temperatures as low as 25 K in the amorphous CO 2 matrix. The ozonides were identified by their infrared spectra, whose assignments were confirmed with the help of an ab initio calculation. The same reaction is imperceptible in a crystalline CO 2 matrix deposited at 65 K, becoming observable only at 77 K and higher temperatures. Molecular dynamics simulations carried out for the solid argon host indicate that a highly organized crystalline structure does not allow the motions required for the reactions. These restrictions are apparently less stringent in the amorphous solid CO 2, suggesting it as a suitable solvent for the study of reactions having a low activation barrier.