Five 1,2-disubstituted, R 1C=CHMR n. and fifteen trisubstituted, R 1C=C(R 2)MR n vinyl radicals were prepared at room temperature in solution by addition of a variety of radicals, ·MR n, to a number of mono- and disubstituted acetylenes. For steric reasons many of these vinyls are relatively long lived. Some decay with first-order and some with second-order kinetics. Their EPR spectra are discussed in terms of "linear" and "bent" structures. It is concluded that only Me 3SiĊ=C(SiMe 3) 2 is truly "linear". In certain systems prolonged reaction leads to the formation of various highly persistent alkyl radicals. The EPR spectra of these alkyls and some of their decay kinetics are also reported. Ten "perpendicular" allyls, (Me 3C) 2ĊC(MR n)=CR 1R 2, of great persistence were prepared by addition of ·MR n to two di-tert-butylvinylidenecy-clopropanes. The EPR spectra of these allyls are compared with those of the corresponding (Me 3C) 2ĊCH 2MR n radicals, since the two types of radicals have similar structures. It is pointed out that in gaining persistence the allyl radicals lose their stabilization.
Journal of the American Chemical Society97, no. 15 (1975): 4269–4275.