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 CO2 at 12-20 K. In the argon matrix, no perceptible re action took place at any temperature below the softening onset of the matrix, while formation of ethylene ozonides (both primary and seconda ry) was observed at temperatures as low as 25 K in the amorphous CO2 m atrix. The ozonides were identified by their infrared spectra, whose a ssignments were confirmed with the help of an ab initio calculation. T he same reaction is imperceptible in a crystalline CO2 matrix deposite d at 65 K, becoming observable only at 77 K and higher temperatures. M olecular dynamics simulations carried out fog the solid argon host ind icate 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 CO2, suggesting it as a suitabl e solvent for the study of reactions having a low activation barrier.