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Chlorine Hyperfine Splittings and Spin Density Distributions of Phenoxy Radicals. An ESR. and Quantum Chemical Study
Author(s) -
Graf Federico,
Loth Klaus,
Günthard HansHeinrich
Publication year - 1977
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19770600304
Subject(s) - chemistry , chlorine , radical , hyperfine structure , chlorine atom , computational chemistry , spin density , quantum chemical , spin (aerodynamics) , chemical shift , spectral line , molecule , organic chemistry , atomic physics , thermodynamics , medicinal chemistry , condensed matter physics , quantum mechanics , physics
ESR. spectra of the chlorine substituted phenoxy radicals listed in Table 1, which were produced by photo‐oxidation of the parent phenols in aprotic solvents, are reported. In most cases the chlorine splittings could be resolved and analysed in detail. Experimental data as well as quantum chemical calculations were used for assignment of all measured chlorine couplings and determination of their relative signs. Spin density distributions and polarization parameters for chlorine are discussed and compared with the results from current semiempirical molecular orbital theories. Chlorine couplings, associated with the larger splittings are found positive in sign, whereas signs of small couplings appear difficult to establish. Limitations in the applicability of McConnell or Karplus ‐ Fraenkel type relations to chlorine substituted aromatic radicals will be discussed and related to peculiar properties of the spin density matrix of such systems.