191722-41-5Relevant articles and documents
Convenient criterion for the distinction between electrophilic and electron transfer reactions of electron-rich alkenes
Bauld, Nathan L.,Aplin, J. Todd,Yueh, Wang,Endo, Stephanie,Loving, Angie
, p. 15 - 24 (2007/10/03)
Both experimental and theoretical studies confirm that the formation of aryl vinyl ether and aryl vinyl sulfide cation radicals from the corresponding neutral substrates correlates with the Brown σ+ parameters as opposed to Hammett σ values. Peak oxidation potentials for both classes of substrates correlate preferentially with σ+, as do gas-phase ionization energies calculated by both semi-empirical and ab initio methods. In contrast, the protonation energies of the same substrates, which relate to carbocation formation, correlate preferentially with σ values, as do rates of protonation and other electrophilic additions. These observations permit a sharp distinction between electrophilic and electron transfer reactions of these two common classes of electron-rich substrates. Using this criterion, the cycloadditions of tetracyanoethylene to these substrates are found to proceed via an electrophilic mechanism, rather than by a previously proposed electron transfer mechanism.
