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Title:Synthesis and Properties of Ortho-Bridged Triarylmethyl Compounds
Author(s):Peters, Norman John
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Organic
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.
Issue Date:1980
Description:106 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.
Other Identifier(s):(UMI)AAI8026571
Date Available in IDEALS:2014-12-13
Date Deposited:1980

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