Photo-CIDNP Studies of 2-Butanone and 3-Pentanone in Solution

The results of photolysis of 2-butanone and 3-pentanone as studied by chemically induced dynamic nuclear polarization (CIDNP) and electron spin resonance spectroscopy (e.s.r.) are reported. In aqueous solutions and t-butanol only the ethyl radical is detected by means of e.s.r., indicating α cleavage to be a major path involving excited states. This observation is further supported by the n.m.r. spectra which are obtained during irradiation of these ketones in D 2 O and a mixture of CD 3 CN-D 2 O (1:1 by volume) containing carbon tetrachloride. Several compounds are detected with their protons spin polarized. A mechanism involving radical reactions is proposed which is consistent with the experimental results.