University of Illinois Urbana-Champaign

Synthesis and Properties of Ortho-Bridged Triarylmethyl Compounds

Peters, Norman John

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Description

Title
Synthesis and Properties of Ortho-Bridged Triarylmethyl Compounds
Author(s)
Peters, Norman John
Issue Date
1980
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
  • The stable carbocation salts 2-tert-butylsesquixanthydryl triflate (2-tert-butyl-4,8,12-trioxadibenzo{cd,mn}pyrenyl trifluoromethanesulfonate) (Ia) and 2,6,10-tri-tert-butylsesquixanthydryl triflate (Ib) are found to be highly delocalized by ('13)C NMR as is expected based on the HMO calculation.
  • Ia R = H IIa R = H
  • Ib R = C(CH(,3))(,3) IIb R = C(CH(,3))(,3)
  • The tert-butylsesquixanthydryl dimers IIa and IIb are vastly more soluble than the unsubstituted dimer. Dimer IIb is only slightly dissociated in solution and reacts only slowly with oxygen. This suggests that the dissociation of the dimer into free radicals is both thermodynamically unfavored and slow despite the possibility of the radical being highly stabilized by delocalization. The dimers are shown to be hexaarylethanes by ('1)H and ('13)C NMR. The X-ray crystal structure of IIa reveals an unusually long C(,ethane)-C(,ethane) bond (1.63 (ANGSTROM)) and short C(,ethane)-C(,phenyl) bonds (1.49 (ANGSTROM)) which may be due to throughbond coupling of the (sigma) and (pi) orbitals.
  • Dimer IIb forms a novel crystalline complex with triflate Ib (1:2). The complex is too weakly associated to be observed in solution and forms crystals too small to be useful for X-ray crystallography. The bonding in this dimer therefore remains undetermined. The small (2%) number of unpaired electrons determined by electron spin resonance spectroscopy suggests that the bonding is extensively delocalized rather than being sesquixanthydryl moieties held together by a one-electron bond.
Graduation Semester
1980
Type of Resource
text
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http://hdl.handle.net/2142/67233

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