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Basicities of a number of ring-substituted N, N-dimethylanilines (DMA) and some related bases in water, acetonitrile, and THF and in the gas phase have been experimentally determined. Gas-phase basicities of DMAs and related bases were calculated at DFT B3LYP 6-311+G** and G3(MP2) levels. Structure-Basicity relationships in these four media were discussed. By comparison of gas-phase basicity shifts induced by stepwise substitution, starting from ammonia and ending at triphenylamine, it was observed that solvent effects of water and acetonitrile exceed the structural effects on intrinsic basicity. It was shown that the influence of substituents in the phenyl ring on DMA basicity is reduced by two to three times when going from the gas phase into the abovementioned condensed media. In the gas phase, 4-NO, 4-NO2, 4-CN, 4-COMe, and 4-CHO substituted DMAs protonate on substituent, whereas in solvents, only 4-NO-DMA probably protonates on substituent. The sensitivity of DMA basicity toward substitution in the phenyl ring was compared with the related family of phenylphosphazene bases, and it was found that the substituent effect is stronger in DMAs by 1.35 times in acetonitrile, 1.45 times in the gas phase, 2.0 times in THF, and 2.6 times in water. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Acidities of different families of acids are examined in media of different physical and chemical nature: water, acetonitrile (AN), 1,2-dichloroethane (DCE) and the gas phase, with special emphasis on strong acids. Included are OH (carboxylic acids, alcohols, and phenols), NH (sulfonamides, imides), and CH (phenylmalononitriles, etc.) acids as well as HCl, HBr, and HI. Dependence of the acidity trends on moving from water to the gas phase on the nature of the acidity center, and the molecular structure are analyzed. The acidity orders are different in water, AN, DCE, and the gas phase. In some cases the differences are dramatic. AN and DCE display similar acidity order in the set of the investigated acids. It is demonstrated that the decisive factor for the behavior of the acids when transferring between different media is the extent of charge delocalization in the anion and that the recently introduced weighted average positive sigma parameter in spite of its simplicity enables interpretation of the trends in the majority of cases. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

17O NMR spectra for 35 ortho-, para-, and meta-substituted phenyl tosylates (phenyl 4-methylbenzenesulfonates), 4-CH3-C6H4SO2OC6H4-X, at natural abundance in acetonitrile at 50 °C were recorded. The 17O NMR chemical shifts, δ(17O), of the sulfonyl (SO2) and the single-bonded phenoxy (OPh) oxygens for para and meta derivatives correlated well with dual substituent parameter treatment using the Taft inductive, σI, and resonance, σºR, constants. The influence of ortho substituents on the sulfonyl oxygen and the single-bonded phenoxy oxygen chemical shifts, δ(17O), was found to be nicely described by the Charton equation: δ(17O)ortho = δ(17O)H + ρI σI + ρR σ°R + δEsB when the data treatment was performed separately for electron-donating + R substituents and electron-attracting − R substituents. Electron-attracting meta and para substituents in the phenyl moiety caused deshielding while the electron-donating meta, para and ortho + R substituents produce shielding effects on the sulfonyl (SO2) and single-bonded phenoxy (OPh) oxygens. The influence of ortho inductive and resonance effects in the case of + R substituents was found to be approximately twice higher than the corresponding influence from the para position. Due to the steric effect of ortho substituents a decrease in shielding of the oxygens at the sulfonyl group ( δEsB > 0, EsB < 0) was detected. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

17O NMR spectra for 44 ortho-, meta- and para-substituted phenyl and alkyl benzoates (C6H5CO2C6H4-X, C6H5CO2R) at natural abundance in acetonitrile were recorded. Substituent effects on the 17O NMR chemical shifts, δ(17O), of the carbonyl oxygen and the single-bonded phenoxy (OPh) and alkoxy (OR) oxygens have been studied. The δ(17O) values of the carbonyl oxygen for para derivatives showed a good correlation with the σ° constants. The δ(17O) values of carbonyl oxygen for ortho derivatives were found to be described well with the Charton equation containing the inductive, σ1, resonance, σ°R, and steric, Es B, substituent constants in case the data treatment was performed separately for electrondonating +R and electron-attracting –R substituents. The electron-donating +R ortho and para substituents in substituted benzoates caused shielding and the electron-withdrawing -R substituents produced deshielding of the O signal. The steric interaction of ortho substituents with the ester group decreased the electron density at the carbonyl oxygen. In alkyl benzoates the δ(17O) values were found to be described well with the inductive, σI, and the steric, Es B, substituent constants. [ABSTRACT FROM AUTHOR]

17O NMR spectra for 29 phenyl esters of ortho‐, para,‐ and meta‐substituted benzoic acids, X‐C6H4CO2C6H5, at natural abundance in acetonitrile were recorded. The δ(17O) values of carbonyl and the single‐bonded oxygens for para derivatives gave good correlation with the σ+ constants. The δ(17O) values for meta derivatives correlated well with the σm constants. The influence of ortho substituents on the δ(17O) values of carbonyl oxygen and the single‐bonded oxygens was analyzed using the Charton equation containing the inductive, σI, resonance, σ+R, and steric, E sB, substituent constants. For ortho derivatives, excellent correlations with the Charton equation were obtained when the data treatment was performed separately for derivatives containing electron‐donating +R and electron‐attracting −R substituents. The electron‐donating substituents in ortho‐, meta‐, and para‐substituted esters resulted in shielding of the 17O signal and the electron‐withdrawing groups caused deshielding. In phenyl ortho‐substituted benzoates, the substituent‐induced positive inductive (ρI > 0), resonance (ρR > 0), and steric (δorthoE sB > 0) effects were found. The steric interaction of ortho substituents with ester group was found to produce a deshielding effect on the carbonyl and single‐bonded oxygens. For ortho derivatives with −R substituents, the resonance term was insignificant and the steric term was ca. twice weaker as compared to that for derivatives with +R substituents. The δ(17O) values for ortho‐substituted nitrobenzenes, acetophenones, and benzoyl chlorides showed a good correlation with the Charton equation as well. In ortho‐substituted nitrobenzenes the inductive, resonance and steric effect were found to be ca. 1.7 times stronger as compared to that for phenyl ortho‐substituted benzoates. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The second-order rate constants k (dm3 mol-1 s-1) for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids in aqueous 5.3 M NaClO4 and 1.0 M Bu4NBr were measured by UV/Vis spectrophotometry at 25 °C. The variations in the ortho inductive, ortho resonance, as well as meta and para polar effects with solvent parameters were studied using data for the alkaline hydrolysis of phenyl esters of substituted benzoic acids in various media. The dependence of the ortho substituent effect on solvent can be precisely described with the following equation: Δlog kortho = log kortho - log kH = 0.059 + 2.19σI + 0.304σ°R + 2.79EsB - 0.016ΔEσI - 0.085ΔEσ°R, where ΔE is the solvent electrophilicity, ΔE = ES - EH2O, characterizing the hydrogen-bond donating power of the solvent. The increase in the meta and para polar substituent effects with decrease in the solvent hydrogen-bond donor capacity (electrophilicity) was approximately to the same extent (-0.068ΔEσ°m,p) as the resonance term for the ortho substituents. The steric term of ortho substituents was independent of the solvent parameters. The variations in the ortho inductive, ortho resonance, as well as meta and para polar substituent effects with the solvent electrophilicity were to the same extent as in phenyl benzoates containing the substituents in the phenyl part. The substituent effects in the alkaline hydrolysis of ethyl benzoates appeared to vary with the solvent electrophilicity nearly to the same extent as in the alkaline hydrolysis of substituted phenyl esters of benzoic acids. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

13C NMR spectra of 37 ortho-, meta-, and para-substituted phenyl benzoates, containing substituents in benzoyl and phenyl moiety, 4 ortho-substituted methyl and 5 ethyl benzoates as well as 9 R-substituted alkyl benzoates have been recorded. The influence of the ortho substituents on the carbonyl carbon 13C NMR chemical shift, δCO, was found to be described by a linear multiple regression equation containing the inductive, σI, resonance, σ°R, and steric, EsB, or υ substituent constants. For all the ortho-substituted esters containing substituents in the acyl part as well as the phenyl part, the substituent-induced reverse inductive effect (ρI < 0), the normal resonance effect (ρR > 0), and the negative steric effect (δortho < 0) with the EsB were observed. In the case of ortho substituents in the phenyl part, the resonance effect was negligible. Due to inductive effect, the ortho electron-withdrawing substituents showed an upfield shift or shielding of the carbonyl carbon, while the electron-donating substituents had an opposite effect. Because of the sterical consequences, ortho substituents revealed a deshielding effect on the 13C NMR chemical shift of the carbonyl carbon. For all the meta- and para-substituted esters, the reverse substituent-induced inductive and resonance effects (ρI < 0, ρR < 0) were found to be significant. In alkyl benzoates, the alkyl substituents showed the reverse inductive and steric effects. The log k values for the alkaline hydrolysis in water, aqueous 0.5 M Bu4NBr and 2.25 M Bu4NBr, and the IR frequencies, νCO, for the ortho-, meta-, and para-substituted phenyl benzoates and alkyl benzoates were correlated nicely with the corresponding 13C NMR substituent chemical shifts, ΔδCO. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The intrinsic gas-phase acidities of CB4XnH5-n and CB5XnH6-n (X ≡ F, Cl or CF3) were calculated using the DFT B3LYP method at the 6-311+G** level. For comparison also the 6-31+G* basis set was used for fluorinated species. The results of the two calculation levels correlated satisfactorily. As the most favourable protonation site of these anions, the facet on the opposite side from the carbon-peaked polyhedron was found. When ordering the substituent groups in terms of increasing acidity of the carboranes, the order F < Cl < CF3 was obtained. [ABSTRACT FROM AUTHOR]

The second-order rate constants k2 (M-1 s-1) for the alkaline hydrolysis of meta-, para- and ortho-substituted phenyl benzoates, C6H5CO2C6H4X, in aqueous 0.5 Mn-Bu4NBr were measured spectrophotometrically. The dependence of substituent effects, especially ortho inductive, resonance and steric terms on different solvent parameters, was studied using the following equation: $$\matrix{\Delta\, \log \, k_{ortho}=& c_0 + c_{1(ortho)} \sigma_{\rm I} + c_{2(ortho)} \sigma _{\rm R}^0 + c_{3(ortho)} E_{\rm s}^{\rm B} + c_4 \Delta E + c_5 \Delta Y + c_6 \Delta P + c_{7(ortho)} \Delta E\sigma _{\rm I}\hfill\cr &+c_{8(ortho)} \Delta Y\sigma_{\rm I} + c_{9(ortho)} \Delta P\sigma _{\rm I} + c_{10(ortho)} \Delta E\sigma _{\rm R}^0 + c_{11(ortho)} \Delta Y\sigma _{\rm R}^0 + c_{12(ortho)} \Delta P\sigma _{\rm R}^0\cr}$$ where Δlog k=log kX-log kH, σI, σR0 and EsB are the inductive, resonance and steric substituent constants and E, Y and P are the solvent electrophilicity, polarity and polarizability parameters, respectively. In data treatment $\Delta E = E_{\rm S} - E_{{\rm H}_2 {\rm O}}, \ \Delta Y = Y_{\rm S} - Y_{{\rm H}_2 {\rm O}} \ {\rm and} \ \Delta P = P_{\rm S} - P_{{\rm H}_2 {\rm O}}$ were used. The solvent electrophilicity was found to be the main factor responsible for changes in the ortho, para and meta polar substituent effects with medium. The variation of the ortho inductive term with the solvent electrophilicity ES was found to be ca threefold smaller than that for para substituents, whereas the ortho resonance term appeared to vary with solvent very similarly to that for para substituents. The steric term of ortho substituents was found to be approximately independent of solvent parameters. The ortho effect caused by the supplementary inductive effect from ortho position was found to disappear in a solvent whose electrophilic solvating power is comparable to that of 60% aqueous ethanol (E ≈ 13.3). Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A method for creating self-consistent acidity and basicity scales in nonaqueous solvents is presented and the current progress in applying such scales to different solvents is reviewed. The method is based on UV-Vis spectrophotometric titration of a mixture of two acids (or two bases) with a non-absorbing base (acid). From the titration data the relative acidity (relative basicity) of the two compounds — the difference of their pKa values (ΔpKa) — is obtained. When a large set of compounds that have different acid (base) strengths is available and ΔpKa measurements are carried out in such a way that each compound is measured against several other compounds, a self-consistent acidity (basicity) scale can be built. The relative acidities (basicities) of the compounds included in the scale can be determined at very high accuracy: many of the error sources, most importantly moisture and impurities in the solvent and in the compounds, influence both compounds in a similar way and at least partially cancel out. Using this method, self-consistent acidity scales have been created in heptane and acetonitrile and self-consistent basicity scales have been developed in acetonitrile and THF. These scales are discussed and future plans are outlined. [ABSTRACT FROM AUTHOR]

Absorption spectra of fullerene C[sub 60] were recorded between 300 and 700 nm in seven different binary solvent mixtures (toluene-acetic acid, toluene-methanol, toluene-acetonitrile, toluene-dimethyl sulphoxide, toluene-dimethylformamide, pyridine-methanol, and pyridinewater). The appearance of the UV-vis spectra of fullerene C[sub 60] was found to be influenced by the composition of the mixture. The influence of the composition of the mixture on the position of four absorption bands (C, A[sub l], δ[sub 1], and γ[sub 2]) was studied. The solvent-induced shifts of the absorption maxima were generally in the range of several nanometers, the longest being 10.3 nm in the mixture of toluene and dimethylformamide. The data were analysed in terms of the preferential solvation model. Fullerene was found to be strongly preferentially solvated by toluene and pyridine compared to the more polar components of the mixtures. The selective solvation model was found to be applicable to the description of solvatochromism of C[sub 60] in binary solvent mixtures, at least formally. Particularly interesting solvent effects — marked changes in the shape of the spectrum — were found in the mixtures toluene-dimethylformamide and pyridine-water. [ABSTRACT FROM AUTHOR]

States that the gas-phase equilibrium acidity of 1H-undecafluorobicyclo[2.2.1]heptane (I), 1H,4H-decafluorobicyclo-[2.2.1]heptane (II), and tris(rifluoromethyl)methane(IV) has been determined by pulsed FT-ICR technique. Comparison study of the thermodynamic acidities of I and IV in DMSO solution.