Measurements of Solvent and Secondary Kinetic Isotope Effects for the Gas-Phase SN2 Reactions of Fluoride with Methyl Halides

O’Hair, Richard A. J.; Davico, Gustavo E.; Hacaloğlu, Jale; Dang, Thuy Thanh; DePuy, Charles H.; Bierbaum, Veronica M.

doi:10.1021/ja00087a061

Cited by 112 publications

(169 citation statements)

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“…The solvent KIEs, as summarized in Table 1, are moderately inverse and consistent with our previous results for solvated S n 2 reactions [17,18]. This effect is attributed to a decrease in bond length within the solvent molecule in the transition state, relative to those bonds in the reactant ion.…”

Section: Kinetic Isotope Effectssupporting

confidence: 89%

“…These effects are multiplicative [17,18]; the KIE for the overall perdeutero reaction is the product of the KIE for the perdeutero alkyl halide reaction and the perdeutero solvent reaction. Errors in branching fractions are estimated to be Ϯ50% due to correction for mass discrimination and the presence of ϳ15% F Ϫ reactant anion from collisional dissociation of the solvated anion upon injection.…”

Section: Kinetic Isotope Effectsmentioning

confidence: 99%

“…For reactions of F Ϫ (H 2 O) with methyl halides, O'Hair et al [17] observed moderately inverse KIEs upon deuteration of the alkyl halide, and more substantial inverse KIEs upon deuteration of the solvent. Hu and Truhlar [10] computationally studied the reaction of F Ϫ (H 2 O) with CH 3 Cl, and their results are in excellent agreement with experiment.…”

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confidence: 99%

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Deuterium kinetic isotope effects in microsolvated gas-phase E2 reactions

Eyet

Villano

Kato

et al. 2007

J. Am. Soc. Mass Spectrom.

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This work describes the first experimental studies of deuterium kinetic isotope effects (KIEs) for the gas-phase E2 reactions of microsolvated systems. The reactions of F Ϫ (H 2 O) n and OH Ϫ (H 2 O) n , where n ϭ 0, 1, with (CH 3 ) 3 CX (X ϭ Cl, Br), as well as the deuterated analogs of the ionic and neutral reactants, were studied utilizing the flowing afterglow-selected ion flow tube technique. The E2 reactivity is found to decrease with solvation. Small, normal kinetic isotope effects are observed for the deuteration of the alkyl halide, while moderately inverse kinetic isotope effects are observed for the deuteration of the solvent. Minimal clustering of the product ions is observed, but there are intriguing differences in the nature and extent of the clustering process. Electronic structure calculations of the transition states provide qualitative insight into these microsolvated E2

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Section: Kinetic Isotope Effectssupporting

confidence: 89%

Section: Kinetic Isotope Effectsmentioning

confidence: 99%

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Deuterium kinetic isotope effects in microsolvated gas-phase E2 reactions

Eyet

Villano

Kato

et al. 2007

J. Am. Soc. Mass Spectrom.

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“…O'Hair et al 18 also observed that the main product of the reaction is free Cl − ion, whereas Cl − ͑H 2 O͒ is minor in F − ͑H 2 O͒ +CH 3 Cl. Viggiano et al investigated branching ratios of the reaction OH − ͑H 2 O͒ n +CH 3 Br ͑n =1͒.…”

Section: B Comparison With the Experimentsmentioning

confidence: 97%

“…16,17 From an experimental point of view, O'Hair et al investigated solvent effects on the S N 2 reaction of fluoride ion with methyl chloride and measured the product ions formed by the reaction F − ͑H 2 O͒ +CH 3 Cl. 18 They detected two ions, Cl − and Cl − ͑H 2 O͒, as products. This result has been interpreted to show that two reaction channels,…”

Section: Introductionmentioning

confidence: 99%

Direct ab initio molecular dynamics study on a microsolvated SN2 reaction of OH−(H2O) with CH3Cl

Tachikawa

2006

The Journal of Chemical Physics

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Reaction dynamics for a microsolvated S N 2 reaction OH − ͑H 2 O͒ +CH 3 Cl have been investigated by means of the direct ab initio molecular dynamics method. The relative center-of-mass collision energies were chosen as 10, 15, and 25 kcal/ mol. Three reaction channels were found as products. These are ͑1͒ a channel leading to complete dissociation ͑the products are CH 3 OH+Cl − +H 2 O: denoted by channel I͒, ͑2͒ a solvation channel ͑the products are Cl − ͑H 2 O͒ +CH 3 OH: channel II͒, and ͑3͒ a complex formation channel ͑the products are CH 3 OH¯H 2 O+Cl − : channel III͒. The branching ratios for the three channels were drastically changed as a function of center-of-mass collision energy. The ratio of complete dissociation channel ͑channel I͒ increased with increasing collision energy, whereas that of channel III decreased. The solvation channel ͑channel II͒ was minor at all collision energies. The selectivity of the reaction channels and the mechanism are discussed on the basis of the theoretical results.

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