The Mercury Photosensitized Decomposition of Ethylenimine

Mercury-photosensitized reactions in the presence of CO: decomposition of ethylenimine

The effect of CO addition on a number of Hg(3P1) photosensitized decompositions, under conditions of incomplete quenching, has been investigated. Compounds having large quenching cross sections (i.e. those presumably decomposing through formation of triplet excited states) have enhanced rates of decomposition in the presence of CO. Those having small cross sections (i.e. those for which the primary interaction is presumably the direct attack of Hg(3P1) atom on a C—H bond) show no enhancement. This difference in behavior, which is interpreted in terms of activation by a HgCO* complex, suggests that CO addition under the appropriate conditions can be used to decide whether or not certain decomposition products aries from an electronically excited precursor. For example, the effect of CO on the sensitized decomposition of ethylenimine indicates that the major dissociation process to form C2H4 and the NH radical proceeds by way of an electronically excited precursor, while a minor process (5%) to form

[Formula: see text] radical and a H-atom does not. Some results on the sensitized decomposition of formaldehyde are also discussed.

The Hg(3P1) photosensitized decomposition of ethylenimine and ethylenimine-d4

Quantum yields as a function of reaction time and substrate pressure (20–200 Torr) have been obtained for the products H2, C2H4, NH3, N2, CH4, and C2H6 (their relative importance decreases in that order). The isotopic composition of the hydrogen from the decomposition of ethylenimine-d4 (El-d4) supports preferential hydrogen-atom detachment from nitrogen. Since addition of substantial amounts of C2H4 did not affect the yield of NH3, the implication of the NH (triplet) in the Hg sensitized decomposition of El is questioned. It is also proposed that the products investigated originate from the degradation of an excited El.