Application of the kinetic method to bifunctional bases

Bouchoux, Guy; Buisson, David‐Alexandre; Bourcier, Sophie; Sablier, Michel

doi:10.1016/s1387-3806(03)00219-7

Cited by 41 publications

(66 citation statements)

References 44 publications

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“…The comparison of these values with those obtained by the kinetic method 3,4 shows again a large discrepancy; the deviation in proton affinities attains here more than 20 kJ‚mol -1 .…”

Section: Resultsmentioning

confidence: 75%

“…It corroborates other investigations, which demonstrate that indeed the kinetic method (even in its full entropy analysis variant) does not provide the true ∆ p S°t erm but only a fraction of it. [3][4][5] However, the precise understanding of the large ∆ p S°values revealed by the equilibrium constant determinations is not yet achieved. Clearly, another mean to estimate the proton affinities and the protonation entropies of the diols 1-3 to control the origin of these cumulated discrepancies is of interest.…”

Section: Resultsmentioning

confidence: 99%

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Protonation Thermochemistry of α,ω-Alkane Diols in the Gas Phase: A Theoretical Study

Bouchoux

Berruyer‐Penaud

2003

J. Phys. Chem. A

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The proton affinities of 1,2-ethane diol (1), 1,3-propane diol (2), and 1,4-butane diol (3) were calculated by ab initio molecular orbital calculations at the G2(MP2) level. The values (PA(1) ) 795.3, PA(2) ) 851.5, and PA(3) ) 882.4 kJ‚mol -1 ) are in agreement with recent determinations using the kinetic method but at variance with previous results obtained from equilibrium constant measurements. Entropy differences, ∆ p S°-M) ) S°(MH + ) -S°(M) (M ) 1-3), were estimated by explicitly considering the rotational barriers of the torsional modes in both the neutral and the protonated molecules, M. Absolute values of calculated ∆ p S°( -5, -22, and -32 J‚mol -1 ‚K -1 for M ) 1, 2, and 3, respectively) are lower than that presently available in the literature. Combining the calculated PA(M) and ∆ p S°(M) leads to gas-phase basicities GB(M) equal to 761.4, 812.4, and 840.4 kJ‚mol -1 for M ) 1, 2, and 3, respectively.

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“…The comparison of these values with those obtained by the kinetic method 3,4 shows again a large discrepancy; the deviation in proton affinities attains here more than 20 kJ‚mol -1 .…”

Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Protonation Thermochemistry of α,ω-Alkane Diols in the Gas Phase: A Theoretical Study

Bouchoux

Berruyer‐Penaud

2003

J. Phys. Chem. A

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“…The directly measured quantity, similarly to the case of AN or THF, is the relative basicity of two bases DDG b , given by Equations (12)- (14).…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

“…Each equilibrium measurement is a measurement of the relative basicity of bases B 1 and B 2 (that is "each arrow" in Table S4 in Supporting Information) according to Equations (12), (13), (14). The partial pressures of the neutrals were measured using the Bayard-Alpert gauge and were corrected for the differences in ionization cross-sections (see ref [27] for details).…”

Section: Measurements Of Gas-phase Basicity (Gb)mentioning

confidence: 99%

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Brønsted Basicities of Diamines in the Gas Phase, Acetonitrile, and Tetrahydrofuran

Rõõm

Kütt

Kaljurand

et al. 2007

Chemistry A European J

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A comprehensive basicity study of alpha,omega-alkanediamines and related bases has been carried out. Basicities in acetonitrile (AN, pK(a) values), tetrahydrofuran (THF, pK(alpha) values), and gas phase (GP, GB values), were measured for 16, 14, and 9 diamine bases and for several related monoamines. In addition the gas-phase basicities and equilibrium geometries were computed for 19 diamino bases and several related monoamines at the DFT B3LYP 6-311+G** level. The effects of the different factors (intrinsic basicity of the amino groups, formation of intramolecular hydrogen bonds, and molecular strain) determining the diamine basicities were estimated by using the method of isodesmic reactions. The results are discussed in terms of molecular structure and solvation effects. The GP basicity is determined by the molecular size and polarizability, the extent of alkylation, and the energy effect of intramolecular hydrogen bond formation in the protonated base. The basicity trends in the solvents differ very much from those in GP: 1) The solvents severely compress the basicity range of the bases studied (3.5 times for the 1,3-propanediamine family in AN, and 7 times in THF), and 2) while stepwise alkylation of the basicity center leads to a steady basicity increase in the gas phase, the picture is complex in the solvents. Significant differences are also evident between THF and AN. The high hydrogen bond acceptor strength of THF leads to this solvent favoring the bases with "naked" protonation centers. In particular, the basicity order of N-methylated 1,3-propanediamines is practically inverse to that in the gas phase. The picture in AN is intermediate between that of GP and THF.

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Evaluation of the protonation thermochemistry obtained by the extended kinetic method

Bouchoux

2006

J. Mass Spectrom.

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An evaluation of the results obtained by the extended kinetic method for a series of representative bases is presented here. Analysis of the original experimental data is conducted using the orthogonal distance regression (ODR) statistical treatment. A comparison with the proton affinities and protonation entropies obtained from variable temperature equilibrium constant measurements demonstrate deviations, which may be ascribed to random and systematic errors. Considerable random errors are associated with the extended kinetic method if the number of reference bases and the range of effective temperatures are too low. It is also confirmed that large systematic errors on proton affinities and protonation entropies are obtained when large protonation entropy is associated with the considered system. It is, however, encouraging to note that the gas phase basicities obtained by the extended kinetic method are generally comparable to that obtained by other methods within a few kJ/mol.

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Application of the kinetic method to bifunctional bases

Cited by 41 publications

References 44 publications

Protonation Thermochemistry of α,ω-Alkane Diols in the Gas Phase: A Theoretical Study

Protonation Thermochemistry of α,ω-Alkane Diols in the Gas Phase: A Theoretical Study

Brønsted Basicities of Diamines in the Gas Phase, Acetonitrile, and Tetrahydrofuran

Evaluation of the protonation thermochemistry obtained by the extended kinetic method

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