Gas-phase association reactions of hydroxide, methoxide, ethoxide, and their deuterated analogs

Kato, Shingo; Dang, Thuy Thanh; Barlow, Stephan E.; DePuy, Charles H.; Bierbaum, Veronica M.

doi:10.1016/s1387-3806(99)00197-9

Cited by 10 publications

(10 citation statements)

References 32 publications

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“…KIEs from differently labeled solvents suggest that the transition states have structures analogous to that for F -(H 2 O) + CH 3 X. Site-specific deuteration effects have also been observed for ion-molecule association kinetics of hydroxide and alkoxide ions. 25 Detailed analysis of the KIEs as well as product branching will be discussed in a future publication. 26…”

Section: Resultsmentioning

confidence: 99%

Deuterium Kinetic Isotope Effects in the Gas-Phase S_N2 Reactions of Solvated Fluoride Ions with Methyl Halides

et al. 2004

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Rate constants and deuterium kinetic isotope effects (KIEs) are measured for gas-phase nucleophilic substitution (SN2) reactions of solvated fluoride ions of F-(methanol) + CH3X (X = Br, I), F-(isopropyl alcohol) + CH3I, and F-(hydrogen fluoride) + CH3I at 300 K. The isotope effects are determined as the rate constant ratio k H/k D for specifically deuterated reactants, that is, methanol (CH3OH, CD3OH, CH3OD, and CD3OD), isopropyl alcohol (i-C3H7OH and i-C3H7OD), hydrogen fluoride (HF and DF), and methyl halides (CH3X and CD3X). The data reveal identical trends to those previously observed for F-(water) + CH3X (O'Hair, R. A. J.; Davico, G. E.; Hacaloglu, J.; Dang, T. T.; DePuy, C. H.; Bierbaum, V. M. J. Am. Chem. Soc. 1994, 116, 3609). The SN2 reactivities decrease as reaction exothermicity decreases (CH3I > CH3Br > CH3Cl) and as the nucleophile is solvated. Moderate inverse kinetic isotope effects (k H/k D < 1) are observed for the deuteration of the methyl halide, whereas substantial inverse KIEs are measured for the deuteration of the hydroxyl group of the solvent (or the deuteration of hydrogen fluoride). Moderate inverse KIEs are also measured for the deuteration of the methyl group in methanol. The observed trends and magnitudes of the isotope effects are rationalized qualitatively in terms of the SN2 transition-state structure and bonding interactions analogous to those in the F-(H2O) + CH3X system.

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Section: Resultsmentioning

confidence: 99%

Deuterium Kinetic Isotope Effects in the Gas-Phase S_N2 Reactions of Solvated Fluoride Ions with Methyl Halides

et al. 2004

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“…Bierbaum et al have focused on gas‐phase isotope exchange reactions using various deuterated and nondeuterated solvent‐type molecules. Measurement of reaction rates using flowing after‐glow techniques has revealed normal and inverse ( k H / k D < 1) kinetic IEs in small molecular clusters that can be used to study solvation and reaction pathways and distinguish isomers 13–19…”

Section: Communicationmentioning

confidence: 99%

Deuterium isotope effects observed during competitive binding chiral recognition electrospray ionization—mass spectrometry of cinchona alkaloid‐based systems

2006

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Deuterium isotope effects are reported for binding between tert-butylcarbamoyl-quinine/quinidine chiral selectors and isotopomeric quasienantiomers of N-(3,5-dinitrobenzoyl)leucine measured using electrospray ionization-mass spectrometry (ESI-MS) and competitive binding. Evaluation of mixtures of each selector with one labeled and one unlabeled enantiomeric selectand of identical configuration showed a significant difference in measured ion abundances of diastereomeric complexes between the selector and each selectand. It was found that in some cases, the complex containing the nondeuterated selectand was 15% more abundant than its deuterated counterpart. On the basis of an assessment of solution- and gas-phase isotope effects reported in the literature, a series of control experiments were performed to study the origin of the effects. On the basis of these measurements, our preliminary conclusion is that the differing gas-phase physicochemical nature of the deuterated versus nondeuterated selectand represents the strongest contribution to the observed effect in this chiral molecular recognition system.

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“…80) Apparent bimolecular rates are measured as a function of helium pressure to derive the rate constants for termolecular association. Association rates are significantly enhanced by deuteration of the alkyl groups (by factors of 1.4῏3.0) whereas deuteration of the bridging hydrogen does not a#ect the association rates.…”

Section: Termolecular Associationmentioning

confidence: 99%

“…80) For example, in association of methoxide with water, the intermediate complex 7 formed from CH 3 O ῌ and H 2 O (rate constant k f ) is likely to have a hydrogen-bonded structure (Scheme 4).…”

Section: Termolecular Associationmentioning

confidence: 99%

“…Detailed analysis of the magnitude and pressure dependence of the association rates has also provided insights into the potential energy surface (singleversus double-well) and dynamical bottleneck for ion῏ molecule association. 80) 5. Fundamental Ion Chemistry of Biological Interest 5.1 S N 2 reaction at nitrogen center Nucleophilic substitution at a nitrogen center is a convenient synthetic path to the formation of C῏N bonds.…”

Section: ) 82)mentioning

confidence: 99%

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Fundamental Aspects of Gas Phase Ion Chemistry Studied Using the Selected Ion Flow Tube Technique

Kato¹

2005

J. Mass Spectrom. Soc. Jpn.

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Gas phase ion chemistry using the selected ion flow tube (SIFT) technique is discussed with the focus on fundamental studies on ion structure, energetics, reactivity, and dynamics: Laser-induced fluorescence (LIF) kinetics/dynamics of N 2 ῍ (v) ions (vibrationally state-selected ion῎molecule reactions; energy transfer processes), mechanisms of prototypical organic ion reactions (S N 2 nucleophilic substitution and kinetic isotope e#ects; hydrogen/deuterium exchange; isotope e#ects in termolecular association), and ion῎molecule reactions with biological implications (S N 2 reactions at a nitrogen center; E CO 2 elimination reactions of alkyl hydroperoxides). Anion chemistry of small nitroalkanes is also presented. A powerful combination of SIFT and negative ion photoelectron spectroscopy is used to study thermochemistry and structure of energetic and exotic ions (alkyl peroxides; anionic derivatives of diazo and azole compounds, cyclooctatetraene, and cyclopentanone). Finally, some of the new directions in SIFT research are discussed, i.e., reactions of ions with polyatomic organic radicals, and chemical ionization mass spectrometry with new detection schemes.

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Gas-phase association reactions of hydroxide, methoxide, ethoxide, and their deuterated analogs

Cited by 10 publications

References 32 publications

Deuterium Kinetic Isotope Effects in the Gas-Phase S_N2 Reactions of Solvated Fluoride Ions with Methyl Halides

Deuterium Kinetic Isotope Effects in the Gas-Phase S_N2 Reactions of Solvated Fluoride Ions with Methyl Halides

Deuterium isotope effects observed during competitive binding chiral recognition electrospray ionization—mass spectrometry of cinchona alkaloid‐based systems

Fundamental Aspects of Gas Phase Ion Chemistry Studied Using the Selected Ion Flow Tube Technique

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Gas-phase association reactions of hydroxide, methoxide, ethoxide, and their deuterated analogs

Cited by 10 publications

References 32 publications

Deuterium Kinetic Isotope Effects in the Gas-Phase SN2 Reactions of Solvated Fluoride Ions with Methyl Halides

Deuterium Kinetic Isotope Effects in the Gas-Phase SN2 Reactions of Solvated Fluoride Ions with Methyl Halides

Deuterium isotope effects observed during competitive binding chiral recognition electrospray ionization—mass spectrometry of cinchona alkaloid‐based systems

Fundamental Aspects of Gas Phase Ion Chemistry Studied Using the Selected Ion Flow Tube Technique

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Deuterium Kinetic Isotope Effects in the Gas-Phase S_N2 Reactions of Solvated Fluoride Ions with Methyl Halides

Deuterium Kinetic Isotope Effects in the Gas-Phase S_N2 Reactions of Solvated Fluoride Ions with Methyl Halides