The Addition of tert‐Butyl (Me₃Ċ) and (tert‐Butoxy)carbonylmethyl (Me₃CO₂CĊH₂) radicals to alkynes in solution studied by ESR spectroscopy

Absolute rate constants and their temperature dependence are determined by time‐resolved electron spin resonance for the addition of Me 3 Ċ to 20 and of Me 3 CO 2 CĊH 2 to six mono‐ and disubstituted alkynes in solution. For Me 3 Ċ the rate constants show polar alkyne‐substituent effects which are, however, weaker than for the corresponding alkenes. For Me 3 CO 2 ĊH 2 , the rate constants do not vary strongly with alkyne substitution and probably increase with increasing reaction exothermicity. Both radicals react generally slower with alkynes than with alkenes which is discussed in terms of the state correlations. Several vinyl‐type radical adducts of Me 3 Ċ to alkenes are characterized by electron spin resonance, and their spectral data indicate linear or bent configurations of the radical carbon depending on the substitution.