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BORON PHOTOCHEMISTRY. XV. DETERMINATION OF THE HAMMETT SUBSTITUENT CONSTANT FOR THE p-DIMESITYLBORYL GROUP
Glogowski, M. E.,Williams, J.L.R.
, p. 137 - 146 (1981)
Hammett signal values reflect relative strengths of the combined inductive and resonance effects of substituents.Using the ionization technique, as well as an independent neutralization method, we found the ?H value for the p-dimesitylboryl group to be 0.42 as compared to 0.78 for the p-nitro group.The value of ?uv,H=0.65 +/- 0.03 determined from pi-electron interaction processes, such as absorption spectra and pi complex formation, is felt to relate better to the p-dimesitylboryl-substituted dyes.A similar function reflecting the pi resonance interaction of substituent groups is the Tomasik-Krygowski ?uv,K value, for which 0.58 was found for the p-dimesitylboryl group compared to 0.66 for the p-nitro group.
