Intramolecular homolytic substitution in selenoxides and selenones

Amber N. Hancock, Sara H. Kyne, Heather M. Aitken, Carl H. Schiesser

Research output: Contribution to journalArticleResearchpeer-review

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 languageEnglish
Pages (from-to)7790-7795
Number of pages6
JournalTetrahedron
Volume72
Issue number48
DOIs
Publication statusPublished - 1 Jan 2016
Externally publishedYes

Keywords

  • Computational chemistry
  • Homolytic substitution
  • Radical
  • Selenium
  • Selenone
  • Selenoxide

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