PHOTOOXIDATION OF BUTENES BY NITROGEN DIOXIDE AT DIFFERENT WAVE LENGTHS

Abstract

Photooxidation of butenes by nitrogen dioxide at room temperature has been studied at three different wave lengths: 2288, 2537, and 3261 Å. In the case of butene-1 an abrupt change in the ratios of reaction products is observed between 2537 and 2288 Å: about three times as much α-butene oxide as n-butyraldehyde is formed at 2288 Å, while the amounts of these two compounds are almost equal at the longer wave lengths. This discontinuity is ascribed to a difference in the mechanism of reaction with olefinic double bonds of the first excited state, O(¹D), and the ground state, O(³P), of oxygen atoms. Experimental evidence indicates that there is collisional quenching of O(¹D) to O(³P) atoms.Reactions of cis- and trans-butene-2 and of isobutene are much less reproducible, particularly so that of isobutene, because of the much more readily occurring thermal reaction of the excess nitrogen dioxide present with the epoxides initially formed.