Nuclear Spin Polarization During the Photolysis of Di-t-buytl Ketone

Di-t-butyl ketone photolyzes in perfluoromethylcyclohexane to give pivalaldehyde, isobutylene, and 2-methylpropane which exhibit enhanced absorption and emission proton magnetic resonances as a result of nuclear spin polarization. Upon addition of CCl4 to the solution, the proton spin polarization in 2-methyl-propane disappears whereas the other products including a new product, t-butyl chloride, still exhibit the effect. Piperylene also prevents proton spin polarization in 2-methylpropane. These results are consistent with a model in which nuclear spin polarization occurs in radical pairs formed via dissociated radicals and via excited states of the ketone. Analysis of the spectra is presented in detail. For this purpose, the quantum yields for reaction from the excited states were obtained from fluorescence quenching experiments and reaction quenching data in the literature.