Electron Paramagnetic Resonance Spectroscopic Characterization of alpha,2-and alpha,4-Didehydrotoluene

The elusive diradicals alpha,2- and alpha,4-didehydrotoluene 1 and 3, have been generated by photolysis of matrix-isolated 2- iodobenzyl iodide 7 and 4-iodobenzyl iodide 8, respectively. Diradical 3 could also be synthesized by flash vacuum thermolysis of 8, with subsequent trapping of the products in argon at 5K. The diradicals in their triplet ground states were characterized by electron paramagnetic resonance spectroscopy. The triplet ground states were in accordance with previous theoretical calculations for these species.