H-bond complexes between 3- or 4-OH phenoxyl radicals and various H-bond accepting molecules were investigated by experimental and computational methods. The H-bond donating ability (a2H) of 2,6-di-tert-butyl-4-hydroxyphenoxyl radical (1) was determined as 0.79 ± 0.05 by measuring, using EPR spectroscopy, the variations of the hyperfine splitting constants of 1 as a function of the acceptor concentrations. A computational approach, based on DFT calculations, was employed to estimate the a2H values for OH-substituted phenoxyl radicals that were not persistent enough to be studied by EPR spectroscopy. The a2H value calculated for the 2,6-di-methyl analogue of 1 was 0.76, in good agreement with EPR experiments. The a2H values for 2-methoxy-4-hydroxy (3), 4-hydroxy (4), 4,6-di-methyl-3-hydroxy (5) and 3-hydroxy (6) phenoxyl radicals were computed as 0.77, 0.84, 0.66 and 0.71, respectively, indicating that a2 H values were dependent on the presence of electron donating substituents and on the relative positions of the –OH and –OΣ groups. By correlating the a2 H values for 4 and 6 with their water and gas-phase acidities, an unexpected role of water in promoting proton dissociation from these radicals was evidenced.

R. Amorati, G. F. Pedulli (2012). Hydrogen bond donating ability of meta and para hydroxy phenoxyl radicals. ORGANIC & BIOMOLECULAR CHEMISTRY, 10, 814-818 [10.1039/c1ob06502e].

Hydrogen bond donating ability of meta and para hydroxy phenoxyl radicals

AMORATI, RICCARDO;PEDULLI, GIAN FRANCO
2012

Abstract

H-bond complexes between 3- or 4-OH phenoxyl radicals and various H-bond accepting molecules were investigated by experimental and computational methods. The H-bond donating ability (a2H) of 2,6-di-tert-butyl-4-hydroxyphenoxyl radical (1) was determined as 0.79 ± 0.05 by measuring, using EPR spectroscopy, the variations of the hyperfine splitting constants of 1 as a function of the acceptor concentrations. A computational approach, based on DFT calculations, was employed to estimate the a2H values for OH-substituted phenoxyl radicals that were not persistent enough to be studied by EPR spectroscopy. The a2H value calculated for the 2,6-di-methyl analogue of 1 was 0.76, in good agreement with EPR experiments. The a2H values for 2-methoxy-4-hydroxy (3), 4-hydroxy (4), 4,6-di-methyl-3-hydroxy (5) and 3-hydroxy (6) phenoxyl radicals were computed as 0.77, 0.84, 0.66 and 0.71, respectively, indicating that a2 H values were dependent on the presence of electron donating substituents and on the relative positions of the –OH and –OΣ groups. By correlating the a2 H values for 4 and 6 with their water and gas-phase acidities, an unexpected role of water in promoting proton dissociation from these radicals was evidenced.
2012
R. Amorati, G. F. Pedulli (2012). Hydrogen bond donating ability of meta and para hydroxy phenoxyl radicals. ORGANIC & BIOMOLECULAR CHEMISTRY, 10, 814-818 [10.1039/c1ob06502e].
R. Amorati; G. F. Pedulli
File in questo prodotto:
Eventuali allegati, non sono esposti

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/111503
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 11
  • ???jsp.display-item.citation.isi??? 10
social impact