The reactions of ozone with propane and ethane☆

Abstract

The reactions of ozone with propane and ethane were studied in the temperature range 0° to 60°C in thermostated infra-red gas cells. The major products of the ozone-propane reaction were found to be carbon dioxide, water vapour, acetone, formic acid and methanol. Major products of the ozone-ethane reaction included all the above with the exception of acetone. In the presence of added oxygen the activation energy for the ozone-propane reaction, calculated on the basis of the expression −d [O 3 ]/d t = k [03] [C 3 H 8 ] was found to be 14·6 kcal mole −1 . The pre-exponential term was 2·12 × 108 l. mole −1 sec −1 . In the absence of added oxygen, the activation energy was found to be 14·3 kcal mole-', and the pre-exponential term to be 1·17 × 108 l. Mole −1 sec −1 , which values are not considered significantly different from those quoted above. In the presence of added oxygen, the activation energy for the ozoneethane reaction, calculated on the basis of the expression −d [03]/dt=k [03] [C 2 H 6 ] was found to be 13·9 kcal mole −1 . The pre-exponential term was 1·24 × 10 8 l. mole −1 sec −1 In the absence of added oxygen, the activation energy was found to be 14·7 kcal mole −1 , and the pre-exponential term was calculated to be 3·50 × 108 l. mole −1 sec −1 .As before, no significant difference is considered to exist between values obtained in the presence and in the absence of added oxygen. The reactions were observed to be substantially independent of Pyrex and sodium chloride surfaces. An approximate equivalence was found between the number of gramme-atoms of oxygen fixed in the products and the number of moles of ozone consumed. The low values obtained for the activation energy are taken to indicate that the initiating agent in the reactions is the ozone molecule.