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The Addition of tert ‐Butyl (Me 3 Ċ) and ( tert ‐Butoxy)carbonylmethyl (Me 3 CO 2 CĊH 2 ) radicals to alkynes in solution studied by ESR spectroscopy
Author(s) -
Rubin Herbert,
Fischer Hanns
Publication year - 1996
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19960790617
Subject(s) - chemistry , radical , alkyne , substituent , reaction rate constant , electron paramagnetic resonance , resonance (particle physics) , adduct , medicinal chemistry , photochemistry , kinetics , organic chemistry , atomic physics , nuclear magnetic resonance , physics , quantum mechanics , catalysis
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.