Chemically induced dynamic nuclear recent studies

Palm and Dreeskamp (42,43) recently reported a CIDNP (Chemically Induced Dynamic Nuclear Polarization) study of the photolysis of a-(3,5-dimethoxyphenoxy)-acetophenone. From the polarization of the methylene protons they concluded that at least two of the products (diphenyl-1,4-butadione and a-(3,5-dimethoxy-4-hydroxyphenyl)-acetophenone) are formed from the singlet excited state. 

The text assumes elementary knowledge of the common organic spectroscopic techniques. Nevertheless, we have included a description of the recently developed method of chemically induced dynamic nuclear polarization (CIDNP), which has already proved to be of great importance in the study of radical reactions and which has not yet found its way into books covering spectroscopy of organic compounds. 

Since the heroic early mechanistic investigations, there have been two developments of major significance in radical chemistry. The first was the advent of electron spin resonance (ESR) spectroscopy (and the associated technique of chemically induced dynamic nuclear polarisation, CIDNP) [24], which provided structural as well as kinetic information the second is the more recent development of a wide range of synthetically useful radical reactions [20]. Another recent development, the combination of the pulse radiolysis and laser-flash photolysis techniques, is enormously powerful for the study of radicals but beyond the scope of this book. 

The technique most recently introduced to study radical cations is chemically induced dynamic polarization (CIDNP), a nuclear resonance method based on the observation of transient signals, substantially enhanced in either absorption or emission. These effects are induced as a result of magnetic interactions in radical or radical ion pairs on the nanosecond timescale. This method requires acquisition of an NMR spectrum during (or within a few seconds of) the generation of the radical ion pairs. The CIDNP technique is applied in solution, typically at room... 

---