Resonance and field/inductive substituent effects on the gas‐phase acidities of <i>para</i>‐substituted phenols: a direct approach employing density functional theory

Barbour, Josiah B.; Karty, Joel M.

doi:10.1002/poc.850

Cited by 21 publications

(12 citation statements)

References 27 publications

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“…38 Geometries were optimized with density functional theory (DFT) at the B3LYP level of theory 39 using the 6-31+G* basis set. This is the same level of theory and basis set as was used in our previous vinylogue studies, 19,40 which have proven to be in excellent agreement with available experimental reaction thermodynamics, as well as with other resonance studies. Furthermore, the enthalpy differences we calculated at that level of theory are in excellent agreement with those obtained at the G2 level of theory (see Results and ref 19).…”

Section: Computational Detailssupporting

confidence: 80%

Y-Aromaticity: Why Is the Trimethylenemethane Dication More Stable than the Butadienyl Dication?

et al. 2005

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[reactions: see text] Resonance energies of the trimethylenemethane dication (1) and the butadienyl dication (4) were evaluated using two independent computational methodologies to provide insight into the validity of Y-aromaticity. One methodology employed density functional theory calculations and examined the resonance contribution of the C=C double bond toward the double hydride abstraction enthalpies of methylpropene (6) and 2-butene (8), yielding 1 and 4, respectively. These resonance contributions by the double bond were determined by calculating the double hydride abstraction enthalpies of both the parallel and perpendicular conformations of vinylogues of 6 and 8, in which n = 1-4 vinyl units were inserted between the central carbon-carbon double bond and each of the reaction centers. Extrapolation of the resonance contribution in each vinylogue to n = 0 yielded the resonance contribution in the respective parent molecules. The second methodology employed an orbital deletion procedure (ODP), which effectively allowed us to examine the energies of individual resonance structures. The resonance energy of each dication is computed as the difference between the most stable resonance structure and that of the delocalized species. The two methodologies are in agreement, suggesting that the resonance energy of the trimethylenemethane dication is substantially greater than that of the butadienyl dication. The origin of this difference in resonance stabilization is discussed.

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Section: Computational Detailssupporting

confidence: 80%

Y-Aromaticity: Why Is the Trimethylenemethane Dication More Stable than the Butadienyl Dication?

et al. 2005

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“…However, this effect should be essentially the same in the deprotonation enthalpy of the corresponding alkylogue of ethanol, so when the inductive/field effect is computed as described above, the impact that this residual negative hyperconjugation has should be effectively cancelled. Indeed, when this type of method was applied to para-substituted phenols, 36 the results were in quite good agreement with the well-known Swain-Lupton resonance and inductive/field parameters. 31…”

Section: Alkylogue Extrapolation Methodssupporting

confidence: 71%

Why is sulfuric acid a much stronger acid than ethanol? Determination of the contributions by inductive/field effects and electron-delocalization effects

Lynch

Maloney

Sowell

et al. 2015

Phys. Chem. Chem. Phys.

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Two different and complementary computational methods were used to determine the contributions by inductive/field effects and by electron-delocalization effects toward the enhancement of the gas-phase deprotonation enthalpy of sulfuric acid over ethanol. Our alkylogue extrapolation method employed density functional theory calculations to determine the deprotonation enthalpy of the alkylogues of sulfuric acid, HOSO2-(CH2CH2)n-OH, and of ethanol, CH3CH2-(CH2CH2)n-OH. The inductive/field effect imparted by the HOSO2 group for a given alkylogue of sulfuric acid was taken to be the difference in deprotonation enthalpy between corresponding (i.e., same n) alkylogues of sulfuric acid and ethanol. Extrapolating the inductive/field effect values for the n = 1-6 alkylogues, we obtained a value of 51.0 ± 6.4 kcal mol(-1) for the inductive/field effect for n = 0, sulfuric acid, leaving 15.4 kcal mol(-1) as the contribution by electron-delocalization effects. Our block-localized wavefunction method was employed to calculate the deprotonation enthalpies of sulfuric acid and ethanol using the electron-localized acid and anion species, which were compared to the values calculated using the electron-delocalized species. The contribution from electron delocalization was thus determined to be 18.2 kcal mol(-1), which is similar to the value obtained from the alkylogue extrapolation method. The two methods, therefore, unambiguously agree that both inductive/field effects and electron-delocalization effects have significant contributions to the enhancement of the deprotonation enthalpy of sulfuric acid compared with ethanol, and that the inductive/field effects are the dominant contributor.

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“…However, electron density of the C2-C3 π-bond increased in the order Cl < NH 2 < NO 2 as a result of the proximity to the substituents which caused substantial π-electron delocalization into the C2-C3 bond. ese interactions increase the electron density on the phenyl ring and contribute to the π-π * interactions [2,30] which shift the λ max to longer wavelengths. Table 5 shows results of the second-order perturbation of the Fock matrix.…”

Section: Resultsmentioning

confidence: 99%

Electronic Spectra of ortho-Substituted Phenols: An Experimental and DFT Study

Tetteh

Zugle

Adotey

et al. 2018

Journal of Spectroscopy

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The electronic spectra of phenol, 2-chlorophenol, 2-aminophenol, and 2-nitrophenol have been studied both experimentally and computationally. The effect of the substituents on the solvatochromic behavior of the phenols were investigated in polar protic (methanol) and aprotic (dimethyl sulfoxide (DMSO)) solvents. The spectra of 2-nitrophenol recorded the highest red shift in methanol. The observed spectral changes were investigated computationally by means of density functional theory (DFT) methods. The gas phase compounds were fully optimized using B3LYP functionals with 6-31++G(d,p) bases set. The effects of the substituents on the electron distribution in the σ-bonds as well as the natural charge on the constituent atoms were analyzed by natural bond orbital (NBO) and natural population analysis (NPA). Second-order perturbation analyses also revealed substantial delocalization of nonbonding electrons on the substituents onto the phenyl ring, thereby increasing its electron density. Full interaction map (FIM) also showed regions of varying propensities for hydrogen and halogen bonding interactions on the phenols.

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Resonance and field/inductive substituent effects on the gas‐phase acidities of para‐substituted phenols: a direct approach employing density functional theory

Cited by 21 publications

References 27 publications

Y-Aromaticity: Why Is the Trimethylenemethane Dication More Stable than the Butadienyl Dication?

Y-Aromaticity: Why Is the Trimethylenemethane Dication More Stable than the Butadienyl Dication?

Why is sulfuric acid a much stronger acid than ethanol? Determination of the contributions by inductive/field effects and electron-delocalization effects

Electronic Spectra of ortho-Substituted Phenols: An Experimental and DFT Study

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