Über die substituentenabhängigkeit der Donatorund Akzeptoreigenschaften der Hydroxylgruppe in parasubstituierten Phenolen und Phenol—Anisol-Komplexen

Seidel, H.; Ritter, C. W.; Fruwert, J.; Geiseler, G.

doi:10.1016/0584-8539(76)80137-7

Cited by 16 publications

(7 citation statements)

References 12 publications

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“…We are not aware of an analogous case with alkenes. This interpretation is consistent with the relatively low HOMO−LUMO gap in disilenes compared with that for alkenes. 2e,, Phenol association cannot account for the concave Hammett plot, since a linear relationship exists between the association constants (in CCl 4 ) of substituted phenols and the Hammett σ values of the substituents 9b 1 Schematic Mechanisms for the Addition Reactions of Substituted Phenols to Disilene 1 …”

mentioning

confidence: 67%

“…(a) In CCl 4 phenols exist as an equilibrium mixture of monomers, dimers, and trimers (see refs b and c), and it is reasonable to assume that the same applies to benzene. The observed first-order kinetics in the phenol suggests that the dimer (or trimer) forms of the phenols are not involved in the rate-determining step.…”

Section: Referencesmentioning

confidence: 99%

“…Plots of the pseudo-first-order rate constants ( k obs ) vs phenol concentrations are shown in Figure imply that the addition reactions are indeed first order in both the disilene and the phenol . The second-order rate constants k for the addition of the various phenols to 1 derived from Figure are summarized in Table .…”

mentioning

confidence: 92%

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The Mechanism of Addition of Phenols to Tetramesityldisilene. Evidence for Both Nucleophilic and Electrophilic Rate-Determining Steps

Apeloig

Nakash

1996

J. Am. Chem. Soc.

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mentioning

confidence: 67%

Section: Referencesmentioning

confidence: 99%

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The Mechanism of Addition of Phenols to Tetramesityldisilene. Evidence for Both Nucleophilic and Electrophilic Rate-Determining Steps

Apeloig

Nakash

1996

J. Am. Chem. Soc.

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“…It is kno~vn, however, that a monomer-trimer model gives a good fit t o the observed shifts over a large concentration range (8), whereas monomer-dimer and monomertetranier models d o not. However, dinierization constants between 0.7 and 1.5 1, mol have been reported (28,29) at concentrations bet~veen 0 and 0.25 M. The cheniical shift for the lowest concentration in Table 2, con~binecl with the shift-concentration data in ref. 9, yields a dimer shift of 6.94 to 8.37 ppm depending on which of the dimerization constants is employed.…”

Section: Caveatmentioning

confidence: 78%

The proton magnetic resonance spectra of phenol in the absence of intermolecular proton exchange

Schaefer¹,

Rowbotham²,

Chum³

1976

Can. J. Chem.

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CHUM. Can. J. Chem. 54, 3666 (1976). The proton magnetic resonance spectra in the absence of inter~nolecular proton exchange for 0.27, 0.59, and 0.79 1l4 solutions of phenol in CC14 are analyzed. The long-range coupling over five bonds between the hydroxyl and ring protons is estimated as 0.33 Hz in the monomer and as 0.20 Hz in the trimer of a monorner-trimer model. Support for the decrease in the coupling 011 trilnerization is found in CNDO/2 and INDO MO FPT calculations. The long-range coupling over six bonds is unobservable, consistent with conformations of the trimer in which the phenol molecules remain planar. Water catalyzes the intermolecular proton exchange and, in its absence, the transfer of hydroxyl protons from ~nolecule to molecule within the associated species is inefficient. TED SCHAEFER, J. B. ROWBOTHAM et KALVIN CHUM. Can. J. Chem. 54, 3666 (1976). The ring proton resonance spectrum of phenol dissolved in CC14 was first analyzed precisely by Castellano et crl. (1). Long-range spin-spin couplings between the hydroxyl proton and the ring protons were not observed, no doubt because of relatively rapid intermo!ecular proton exchange. Such coupling constants are easily observed when strong intramolecular hydrogen bonding to carbonyl or nitro groups exists (2-4). More recently, stereospecific long-range couplings involving the hydroxyl proton have been used to deduce the relative strengths of intramolecular hydrogen bonds to halogen substituents (4-6).In this paper experiments are described which succeed in reducing the rate of intermolecular hydroxyl proton exchange in CCI4 solutions of phenol to the extent that long-range couplings to the ring protons become observable. Self association of phenol in CC14 has been extensively investigated (7-111, so that the present [Research assoclate. summer 1975. coupling data throw some light on the conformation of the phenol molecule in the associated state and on the perturbation of the couplings caused by self association. Some inferences about the mechanism of proton exchange in nonaqueous solutions are also made. ExperimentalThe assumption that water catalyzes the intermolecular proton exchange in CC14 solution dictated the method of sample preparation. Zone refined phenol from Aldrich Chemical Co., rated at 99.9(+)',; purity, with an mp of 40.68 C, and CC14 from Fisher, containing 0.02', of water (certified A.C.S.), were used in the following procedure.Sample tubes, stopcock attachments for purposes of degassing by the freeze-pump-thaw technique, pipettes containing small wads of white Kleenex tissue, and 5 ml vials containing molecular sieve, were kept in beakers on a hot plate in a dry box. The temperature at the bottom of the beaker ranged from 180 to 210-C. After 3 days ~~n d e r these conditions, solutions of phenol in CC14, containing a littlc tetramethylsilane and prepared on a balance outside the dry box. were added to the vials containing the rnolec~rlar sieve. These vials were stoppered and left for a day in the dry box, well away from the ho...

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“…It is known [26,36] that phenols form with anisole and similar solvents H-complexes of two types: OH...O and OH...p. The lowest frequency IR band was observed for the first of them (Table 3). With solvatochromic equations (8) and (9) In the OH stretching absorption region of the IR spectra of the solutions of phenol IV in anisole, phenetole, and diphenyl ether, too, we observe two bands.…”

Section: Molecular Structure and Formation Energy Of Salvation H-compmentioning

confidence: 99%

Solvatochromism of Heteroaromatic Compounds: XXV. Effect of Bifurcate Hydrogen Bond with a Weak Intramolecular Component on the IR, NMR, and UV Spectra of 2,6-Dibromo-4-nitrophenol

et al. 2005

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Dissolution of 2,6-dibromo-4-nitrophenol in aprotic protophilic solvents forms a three-center solvation H-complex with a sharply weakened intramolecular hydrogen bond. This weakening is associated with a deformation of the bond angle of the hydroxy group. It is only on interaction with weak p-bases that the intramolecular component of the bifurcate hydrogen bond appreciably affects the spectral position of the OH stretching vibration band; this results in a nonlinear dependence between vOH and the Kamlet3Taft solvatochromic parameter.In work [2], based on a phenomenological notion of complexes with a bifurcate (three-center) hydrogen bond comprising both an intra-and an intermolecular components, has predicted the effect of the formation energy of such complexes on their n XH vibration frequency. For compounds with a weak intramolecular hydrogen bond, two possibilities have been predicted: a monotonic nonlinear or nearly linear dependence of n XH on the H-bond affinity the subunit of the complex.To test this hypothesis, in the present work we have studied 2,6-dibromo-4-nitrophenol, a compound with a weak intramolecular OH...Br bond [3315], by means of IR, NMR, and UV spectroscopy and quantum chemistry.

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Über die substituentenabhängigkeit der Donatorund Akzeptoreigenschaften der Hydroxylgruppe in parasubstituierten Phenolen und Phenol—Anisol-Komplexen

Cited by 16 publications

References 12 publications

The Mechanism of Addition of Phenols to Tetramesityldisilene. Evidence for Both Nucleophilic and Electrophilic Rate-Determining Steps

The Mechanism of Addition of Phenols to Tetramesityldisilene. Evidence for Both Nucleophilic and Electrophilic Rate-Determining Steps

The proton magnetic resonance spectra of phenol in the absence of intermolecular proton exchange

Solvatochromism of Heteroaromatic Compounds: XXV. Effect of Bifurcate Hydrogen Bond with a Weak Intramolecular Component on the IR, NMR, and UV Spectra of 2,6-Dibromo-4-nitrophenol

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