Astatophenols

This preparative scheme leads to only 30% yield due to the side reactions between the meto-astatoaniline diazonium salt and astato-phenol, which cannot be eliminated even by continuous extraction of the product with n-heptane (167). All the astatophenols synthesized to date have been identified by either HPLC (99,104) or TLC (160,166,167). Their dissociation constants (KJ have been established from extraction experiments by measuring the relative distribution of compounds between aqueous borax buffer solutions and n-heptane as a function of acidity. On the basis of these derived values, the Hammett a-constants and hence the field (F) and resonance (R) effects have been estimated for these compounds (167) (see Table VI). The field effect for astatine was found to be considerably weaker than that for other halogens the resonance effect was similar to that for iodine (162). 

Dissociation Constants (X.) and Estimated Hammett -Constants, Field (F), and Resonance (J ) Effects for Astatophenols ... 

Astatophenols, 31 64-65 dissociation constants, Hammett s-constants, field, and resonance effects, 31 66... 

Fibrillin, calcium binding, 46 473, 474, 477 Fibulin-I, calcium binding, 46 473 Field desorption mass spectroscopy, 28 6, 21 Field effects, of astatophenols, 31 66 Fine structure, 13 193-204 Fingerprinting of polymetalates, 19 246-248 Finite perturbation theory, 22 211, 212 First transition series, substitution, transferrins, 41 423 26... 

Hammett s-constants, of astatophenols, 31 66 Hansenula anomala, flavocytochrome bj from, 36 260-261... 

Resonance coupling, Fe—S dimers, 38 446-451 Resonance delocalization, 38 426 Resonance effects, of astatophenols, 31 66 Resonance fluorescence, 46 156 nuclear, 6 438-445 theory of, 6 433 38... 

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