Abstract
G3(MP2)-RAD calculations provide activation energies for intramolecular homolytic substitution in the 4-(alkylselenoxo)butyl and 4-(alkylselendioxo)butyl radicals ranging from 21–39 kJ mol−1, and 143–170 kJ mol−1for the selenoxide and selenone, respectively. Arrhenius data translate into rate constants for ring-closure of 1.5×105−2.5×108s−1(80°) for the selenoxides, and 5.4×10−14−5.1×10−11s−1(80°) for the corresponding selenones. NBO analyses show alkyl radicals are electrophilic during homolytic substitution at selenoxide selenium. The dominant orbital interaction in the transition state is worth 2413 kJ mol−1and involves the SOMO and the lone-pair of electrons on selenium. The corresponding selenones are calculated to ring-close through transition states in which alkyl radicals are nucleophilic, but involve weak (SOMO-> σ* and SOMO-> π*) interactions. Consequently, this chemistry is not viable for selenones because of the lack of lone-pairs of electrons on the chalcogen.
Original language | English |
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Pages (from-to) | 7790-7795 |
Number of pages | 6 |
Journal | Tetrahedron |
Volume | 72 |
Issue number | 48 |
DOIs | |
Publication status | Published - 1 Jan 2016 |
Externally published | Yes |
Keywords
- Computational chemistry
- Homolytic substitution
- Radical
- Selenium
- Selenone
- Selenoxide