5: Structure of the Methyl Radical (CIT)

In 1958 colleagues and I prepared CH3 with C-13 in a low temperature matrix. We reported the paramagnetic resonance of this radical and concluded that it must be essentially planar based on our analysis of the proton and C-13 hyperfine structure. See (52).  I was told that at this time that G. Herzberg said it was not planar, but pyramidal. Later George Pimentel (who had been hosting Herzberg at Berkeley) told me that the best evidence for the structure was our work that favored planarity. Many subsequent theoretical calculations based on the hyperfine structure have supported our conclusion regarding the planarity of the radical. For examples see Chipman[16] and Karplus and Fraenkel[17].



Chapter 6: Intramolecular Charge Transfer in Aromatic Free Radicals