Intramolecular homolytic substitution in selenoxides and selenones

Hancock, Amber N. and Kyne, Sara H. and Aitken, Heather M. and Schiesser, Carl H. (2016) Intramolecular homolytic substitution in selenoxides and selenones. Tetrahedron, 72 (48). 7790 - 7795. ISSN 0040-4020

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Item Type:Article
Item Status:Live Archive

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−1 for the selenoxide and selenone, respectively. Arrhenius data translate into rate constants for ring-closure of 1.5×105−2.5×108 s−1 (80°) for the selenoxides, and 5.4×10−14−5.1×10−11 s−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−1 and 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.

Keywords:Computational chemistry, Selenone, Selenoxide, Selenium, Homolytic substitution, Radical, NotOAChecked
Subjects:F Physical Sciences > F190 Chemistry not elsewhere classified
F Physical Sciences > F100 Chemistry
Divisions:College of Science > School of Chemistry
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ID Code:25238
Deposited On:24 Nov 2016 11:52

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