Laser-jet delayed trapping: electron-transfer trapping of the photoenol from 2-methylbenzophenone

During the course of the development of the argon ion laser-jet technique for the study of high-intensity photochemistry, it became apparent that the laser jet provided a unique opportunity for the trapping of relatively long-lived photochemical intermediates. Thus, the jet solution containing the photochemical substrate could be passed through the focal region of the laser just before it was injected into a fountain of a solution containing the photochemical substrate could be passed through the focal region of the laser just before it was injected into a fountain of a solution containing the trapping agent. Through the partitioning of the photochemical and trapping steps in this way, it should be possible to employ unusual trapping agents that would quench the formation of the photointermediate or would themselves initiate undesired photochemistry, if they were present during the irradiation phase. One can estimate on the basis of the parameters of the current jet apparatus that photochemical intermediates with lifetimes of about 10/sup -2/ s or greater should be amenable to trapping by this delayed trapping technique. The E-photoenol derived from 2-methylbenzophenone would seem to be an ideal candidate for this type of trapping experiment since it is known to have a lifetime of several seconds. In this report, they describe the first application of this laser-jet delayed trapping technique and the unusual photoenol chemistry observed during the course of this study.