PMID- 12392436
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20021231
LR  - 20190708
IS  - 0002-7863 (Print)
IS  - 0002-7863 (Linking)
VI  - 124
IP  - 43
DP  - 2002 Oct 30
TI  - The role of hydrogen bonding on the h-atom-donating abilities of catechols and 
      naphthalene diols and on a previously overlooked aspect of their infrared 
      spectra.
PG  - 12881-8
AB  - Catechols and 1,8-naphthalene diols contain one "free" hydroxyl and one 
      intramolecularly H-bonded hydroxyl group. The "free" hydroxyls are strong 
      hydrogen-bond donors (HBDs) with alpha2H values (Abraham et al. J. Chem. Soc., 
      Perkin Trans. 2 1989, 699) ranging from 0.685 to 0.775, indicating that these 
      compounds have similar HBD properties to those of strongly acidic phenols such as 
      4-chlorophenol (alpha2H = 0.670) and 3, 5-dichlorophenol (alpha2H = 0.774). 
      Kinetic effects on H-atom abstractions from the diols in HB acceptor (HBA) 
      solvents can be quantitatively accounted for over at least 50% of the available 
      range of solvent HBA activities (as measured by their beta2H values; see Abraham 
      et al. J. Chem. Soc. Perkin Trans. 2 1990, 521) on the basis of a single reactive 
      OH group, the "free" OH. This free OH group is an outstanding H-atom donor in 
      poor HBA solvents; e.g., in hexane rate constants for reaction with the DPPH* 
      radical are 2.1 x 104 M-1 s-1 for 3,5-di-tert-butyl catechol and 2 x 106 M-1 s-1 
      for 4-methoxy-1,8-naphthalene diol, but only 7.4 x 103 M-1 s-1 for 
      alpha-tocopherol (vitamin E). The diols are much more reactive than simple 
      phenols because the O-H bond dissociation enthalpy of the "free" OH group is 
      weakened by 5-9 kcal/mol by the intramolecular H-bond. The IR spectra of all the 
      diols in CCl4 show two fairly sharp O-H stretching bands of roughly equal 
      intensity separated by 42-138 cm-1. Addition of a low concentration of DMSO, a 
      strong HBA, causes the band due to the intramolecularly H-bonded OH group to 
      decrease in intensity to roughly half the extent that the "free" OH band loses 
      intensity. The latter forms an intermolecular H-bond with the DMSO, the former 
      does not. What has been overlooked in earlier work is that as the DMSO 
      concentration is increased the band due to the intramolecularly H-bonded OH group 
      first broadens and then evolves into a new, lower frequency (by 19-92 cm-1) band. 
      The magnitude of the shift in the frequency of the intramolecular OH band caused 
      by H-bonding of HBAs to the "free" OH group, Deltanu, increases linearly as the 
      HBA activity of the additive increases, e.g., for 3,5-di-tert-butylcatechol, 
      Deltanu/cm-1 = 33.8 beta2H (R 2 = 0.986). This may provide a new and simple 
      method for determining beta2H values.
FAU - Foti, Mario C
AU  - Foti MC
AD  - Istituto di Chimica Biomolecolare del CNR - Sezione di Catania, Via del Santuario 
      110, I-95028 Valverde (CT), Italy. foti@issn.ct.cnr.it
FAU - Barclay, L Ross C
AU  - Barclay LR
FAU - Ingold, K U
AU  - Ingold KU
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Am Chem Soc
JT  - Journal of the American Chemical Society
JID - 7503056
EDAT- 2002/10/24 04:00
MHDA- 2002/10/24 04:01
CRDT- 2002/10/24 04:00
PHST- 2002/10/24 04:00 [pubmed]
PHST- 2002/10/24 04:01 [medline]
PHST- 2002/10/24 04:00 [entrez]
AID - ja020757l [pii]
AID - 10.1021/ja020757l [doi]
PST - ppublish
SO  - J Am Chem Soc. 2002 Oct 30;124(43):12881-8. doi: 10.1021/ja020757l.