Synthetic and computational studies on organosulfur radical cations and alpha-metalated sulfides

Persistent Link:
http://hdl.handle.net/10150/284212
Title:
Synthetic and computational studies on organosulfur radical cations and alpha-metalated sulfides
Author:
Lorance, Edward Donald
Issue Date:
2000
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The oxidation potentials and electrooxidation mechanism of 3,6-di substituted-1,2-dichalcogenins was investigated by cyclic voltammetry. An EC mechanism was found experimentally and the basis for the chemical step was found computationally to be a change in the planarity of the ring on electron transfer. Photoelectron spectra were obtained of 3,6-disubstituted-1,2-dichalcogenins a different ionizing photon energies. The interpretation of the photoelectron spectra was assisted by computational simulation. A narrow ionization band was found, and was assigned as the sulfur-sulfur σ orbital by computation and comparison of ionization cross-sections. Computational simulation of the excited state determined that this orbital is paired with a low-energy σ* orbital. Electronic transitions to the σ* orbital were found to be common in disulfides, and the low energy of the σ* orbital in 1,2-dichalcogenins causes their unusual color. The computed geometry of the excited state, coupled with ¹H NMR and ⁷⁷Se NMR data, also provided evidence of the limited anti-aromaticity of 1,2-dithiins. A systematic study of the α-deprotonation of dialkyl sulfides was made with Lochmann's/Schlosser's base. The products were analyzed by GC/MS, and the extent of both deprotonation and decomposition was assessed. Mechanisms of decomposition were evaluated. 4-tert-Butylthiane was alpha-deprotonated and stannylated in good yield, in a 38:1 cis:trans ratio. The oxidation potentials of various α-stannylated dialkyl sulfides were analyzed by cyclic voltammetry. The dependence of oxidation and ionization potential on the C-S-C-Sn dihedral angle was investigated computationally, and was found to obey a Karplus-Barfield-type relationship, with an ionization potential minimum near 90°. The computational predictions were borne out in the oxidation potential of cis-2-trimethylstannyl-4-tert-butylthiane (1.17 V), which was found to be slightly lower than the underivatized sulfide but much higher than other alpha-stannylated sulfides due to the 180°C-S-C-Sn dihedral angle. Various computational techniques were used to find evidence of the cyclic interaction of p-type lone pair orbitals in tetrathiatetraasterane. The neutral species and the radical cation were computationally predicted to be possess the same symmetry (D₄(h)) and cyclic interaction of sulfur lone pair orbitals, but oxidation to the dication was predicted to break a carbon-carbon bond.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, Organic.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemistry
Degree Grantor:
University of Arizona
Advisor:
Glass, Richard S.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleSynthetic and computational studies on organosulfur radical cations and alpha-metalated sulfidesen_US
dc.creatorLorance, Edward Donalden_US
dc.contributor.authorLorance, Edward Donalden_US
dc.date.issued2000en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe oxidation potentials and electrooxidation mechanism of 3,6-di substituted-1,2-dichalcogenins was investigated by cyclic voltammetry. An EC mechanism was found experimentally and the basis for the chemical step was found computationally to be a change in the planarity of the ring on electron transfer. Photoelectron spectra were obtained of 3,6-disubstituted-1,2-dichalcogenins a different ionizing photon energies. The interpretation of the photoelectron spectra was assisted by computational simulation. A narrow ionization band was found, and was assigned as the sulfur-sulfur σ orbital by computation and comparison of ionization cross-sections. Computational simulation of the excited state determined that this orbital is paired with a low-energy σ* orbital. Electronic transitions to the σ* orbital were found to be common in disulfides, and the low energy of the σ* orbital in 1,2-dichalcogenins causes their unusual color. The computed geometry of the excited state, coupled with ¹H NMR and ⁷⁷Se NMR data, also provided evidence of the limited anti-aromaticity of 1,2-dithiins. A systematic study of the α-deprotonation of dialkyl sulfides was made with Lochmann's/Schlosser's base. The products were analyzed by GC/MS, and the extent of both deprotonation and decomposition was assessed. Mechanisms of decomposition were evaluated. 4-tert-Butylthiane was alpha-deprotonated and stannylated in good yield, in a 38:1 cis:trans ratio. The oxidation potentials of various α-stannylated dialkyl sulfides were analyzed by cyclic voltammetry. The dependence of oxidation and ionization potential on the C-S-C-Sn dihedral angle was investigated computationally, and was found to obey a Karplus-Barfield-type relationship, with an ionization potential minimum near 90°. The computational predictions were borne out in the oxidation potential of cis-2-trimethylstannyl-4-tert-butylthiane (1.17 V), which was found to be slightly lower than the underivatized sulfide but much higher than other alpha-stannylated sulfides due to the 180°C-S-C-Sn dihedral angle. Various computational techniques were used to find evidence of the cyclic interaction of p-type lone pair orbitals in tetrathiatetraasterane. The neutral species and the radical cation were computationally predicted to be possess the same symmetry (D₄(h)) and cyclic interaction of sulfur lone pair orbitals, but oxidation to the dication was predicted to break a carbon-carbon bond.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, Organic.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorGlass, Richard S.en_US
dc.identifier.proquest9983898en_US
dc.identifier.bibrecord.b4082567xen_US
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