Predicting the rates of proton transfer reactions: a simple model using equilibrium constants and distortion energies

Guthrie, J. Peter

doi:10.1002/(sici)1099-1395(199808/09)11:8/9<632::aid-poc47>3.0.co;2-1

Cited by 19 publications

(5 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the one hand, protonation of the nitroaromatic radical anion (1 in Scheme 1) might have limited the overall NAC reduction and caused the AKIEN-values to decrease to values around 1.01. However, H + -transfer reactions to oxygen are usually near diffusion limit (28,29), and it is unclear whether they could become rate-determining under the chosen experimental conditions. Isotope-sensitive changes in the N-O bonding upon protonation of oxygen atoms are likely too small to cause a significant isotope effects at the nitrogen atom but one could postulate that small 15 N fractionation reflects equilibrium isotope effects upon the first electron transfer.…”

Section: Resultsmentioning

confidence: 99%

Variability of Nitrogen Isotope Fractionation during the Reduction of Nitroaromatic Compounds with Dissolved Reductants

Hartenbach

Hofstetter

Aeschbacher

et al. 2008

Environ. Sci. Technol.

115

View full text Add to dashboard Cite

Compound-specific nitrogen isotope analysis was shown to be a promising tool for the quantitative assessment of abiotic reduction of nitroaromatic contaminants (NACs) under anoxic conditions. To assess the magnitude and variability of 15N fractionation for reactions with dissolved reductants, we investigated the reduction of a series of NACs with a model quinone (anthrahydroquinone-2,6-disulfonate monophenolate; AHQDS-) and a Fe(II)-catechol complex (1:2 Fe(II)-tiron complex; Fe(II)L2(6-)) over the pH range from 3 to 12 and variable reductant concentrations. Apparent kinetic isotope effects, AKIEN, for the reduction of four mononitroaromatic compounds by AHQDS- ranged from 1.039 +/- 0.003 to 1.045 +/- 0.002 (average +/- 1sigma), consistent with previous results for various mineral-bound reductants. 15N fractionation for reduction of 1,2-dinitrobenzene and 2,4,6-trinitrotoluene by AHQDS- and that of 4-chloronitrobenzene by Fe(II)L2(6-), however, showed substantial variability in AKIEN-values which decreased from 1.043 to 1.010 with increasing pH. We hypothesize that the isotope-sensitive and rate-limiting step of the overall NAC reduction can shift from the dehydration of substituted N,N-dihydroxyanilines (large 15N fractionation upon N-O bond cleavage) to protonation or reduction of nitroaromatic radical anions (small 15N isotope effect upon electron transfer) consistent with calculations of semiclassical 15N isotope effects. Our results imply that a quantitative assessment of NAC reduction using compound-specific isotope analysis (CSIA) might need to account for homogeneous and heterogeneous reactions separately.

show abstract

Section: Resultsmentioning

confidence: 99%

Variability of Nitrogen Isotope Fractionation during the Reduction of Nitroaromatic Compounds with Dissolved Reductants

Hartenbach

Hofstetter

Aeschbacher

et al. 2008

Environ. Sci. Technol.

115

View full text Add to dashboard Cite

show abstract

“…No Barrier Theory has been shown to work for an extensive series of proton-transfer reactions over a wide range of reactivity for C−H acids, and now for carbonyl hydration reactions over a wide range of reactivity. The approach seems likely to be very generally applicable.…”

Section: Discussionmentioning

confidence: 99%

“…We have devised a new approach, which we call “No Barrier Theory”, − for calculating rate constants for chemical reactions from the experimental equilibrium constants. The approach shows great promise of providing a general method for calculating the rate constants for chemical reactions with no adjustable parameters.…”

Section: Introductionmentioning

confidence: 99%

Hydration of Carbonyl Compounds, an Analysis in Terms of No Barrier Theory: Prediction of Rates from Equilibrium Constants and Distortion Energies

and

Pitchko

2000

J. Am. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

“No Barrier Theory” postulates that when only one thing happens there is a quadratic relation between energy and reaction progress, with no kinetic barrier. The kinetic barrier seen with essentially all real chemical processes results from the need for more than one thing to happen simultaneously. This approach permits calculation of free energies of activation for covalent hydration of carbonyl compounds, over the range of reactivity for which data are available, from formaldehyde to carboxamides. Acid- and base-catalyzed and uncatalyzed reactions can be treated with no adjustable parameters, with root-mean-square errors of 1.41, 1.30, and 1.50 kcal/mol in free energy of activation. The method requires equilibrium constants and distortion energies. The latter can be calculated by molecular orbital theory using relatively low levels of theory. The calculations can be inverted to calculate equilibrium constants from experimental rate constants.

show abstract

“…The limit of quantification for the spectra was set at ten standard deviations of the background noise registered for a blank sample (Franke and Beauchamp 2017). Proton transfer reaction rate constants used for quantitative analysis were based on the literature (Guthrie 1998;Zhao and Zhang 2004;Cappellin et al 2012). When no data was available a rate of 2.0 × 10 −9 cm 3 s −1 was used.…”

Section: Ptr-ms Analysismentioning

confidence: 99%

Rapid Evaluation of Poultry Meat Shelf Life Using PTR-MS

et al. 2018

View full text Add to dashboard Cite

The use of proton transfer reaction mass spectrometry (PTR-MS) for freshness classification of chicken and turkey meat samples was investigated. A number of volatile organic compounds (VOCs) were selected based on the correlation (> 95%) of their concentration during storage at 4°C over a period of 5 days with the results of the microbial analysis. In order to verify if the selected compounds are not sample-specific, a number of samples sourced from various retailers were classified using the concentration of these compounds in the samples' volatile fraction as input variables. The classification was performed using the support vector machines (SVM) supervised pattern recognition algorithm. It was concluded that it is possible to evaluate the shelf life of meat samples obtained from the same source based on the results of a prior analysis. The PTR-MS fingerprint approach might supplement the currently used methods of shelf life evaluation of poultry due to the short time and nondestructive nature of measurement and ease of quantitative analysis.

show abstract

Predicting the rates of proton transfer reactions: a simple model using equilibrium constants and distortion energies

Cited by 19 publications

References 55 publications

Variability of Nitrogen Isotope Fractionation during the Reduction of Nitroaromatic Compounds with Dissolved Reductants

Variability of Nitrogen Isotope Fractionation during the Reduction of Nitroaromatic Compounds with Dissolved Reductants

Hydration of Carbonyl Compounds, an Analysis in Terms of No Barrier Theory: Prediction of Rates from Equilibrium Constants and Distortion Energies

Rapid Evaluation of Poultry Meat Shelf Life Using PTR-MS

Contact Info

Product

Resources

About