E2C mechanism in elimination reactions. VII. Secondary kinetic hydrogen isotope effects in E2 reactions of alicyclics

Cook, David B.; Hutchinson, R. E. J.; Parker, A. J.

doi:10.1021/jo00934a018

Cited by 7 publications

(4 citation statements)

References 6 publications

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“…Secondary kinetic isotope effects of baseinduced dehydrotosylations and dehydrobrominations of cyclohexyl derivatives were reported to lie between 1.13 and 1.15 for deuterium substitution corresponding to C 1 -SKIE and between 1.15 and 1.25 for substitution corresponding to C 2 -SKIE. 39 Thus, the C 2 -SKIE is measured to be larger than C 1 -SKIE, but not to the extent indicated by the present theoretical results. In better agreement with our results are the gas phase results of diethyl ether with OHwhere a C 2 -SKIE of 1.55 ( 0.03 and a C 1 -SKIE of 1.00 ( 0.02 were obtained.…”

Section: Resultscontrasting

confidence: 76%

“…The inverse effects were suggested to be indications of syn eliminations. Secondary kinetic isotope effects of base-induced dehydrotosylations and dehydrobrominations of cyclohexyl derivatives were reported to lie between 1.13 and 1.15 for deuterium substitution corresponding to C 1 -SKIE and between 1.15 and 1.25 for substitution corresponding to C 2 -SKIE . Thus, the C 2 -SKIE is measured to be larger than C 1 -SKIE, but not to the extent indicated by the present theoretical results.…”

Section: Resultscontrasting

confidence: 64%

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Kinetic Isotope Effects and Transition State Geometries. A Theoretical Investigation of E2 Model Systems

Glad¹,

Jensen²

1997

J. Org. Chem.

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Ab initio calculations at the MP2/6-31+G level have been performed on E2 model systems to investigate whether differences in kinetic isotope effects correlate with changes in transition state geometries. By combining various nucleophiles (NH(2)(-), OH(-), F(-), PH(2)(-), SH(-), Cl(-)) and leaving groups (NH(3), Br(-), Cl(-), F(-), SH(-)) for reactions of the type Nu(-) + CH(3)CH(2)X, a large diversity of transition structures from reactant-like to product-like are generated. For each reaction one primary and two different alpha-secondary kinetic isotope effects are calculated. The primary kinetic isotope effects depend strongly on the nucleophilic placement in the periodic system, which mainly is due to differences in equilibrium isotope effects. When this effect is subtracted, the primary kinetic isotope effects display the expected maximum for symmetric transition structures, although the maximum is broad. The secondary kinetic isotope effects associated with the leaving group provide a qualitative correlation with the hybridization at the carbon, but the corresponding effects at the carbon where the hydrogen abstraction takes place is uncorrelated with the transition state geometry.

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Section: Resultscontrasting

confidence: 76%

Section: Resultscontrasting

confidence: 64%

Kinetic Isotope Effects and Transition State Geometries. A Theoretical Investigation of E2 Model Systems

Glad¹,

Jensen²

1997

J. Org. Chem.

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“…Since the substrate is doubly deuterated in the 3-position, the deuterium not being transferred may introduce a secondary KIE affecting the size of the observed primary KIE. Experimentally determined secondary KIEs for the corresponding position have been reported for the dehydrobromination and dehydrotosylation of cyclohexyl derivatives . These studies suggest that the size of such a KIE may be in the range of 1.15−1.25.…”

Section: Discussionmentioning

confidence: 87%

“…Experimentally determined secondary KIEs for the corresponding position have been reported for the dehydrobromination and dehydrotosylation of cyclohexyl derivatives. 29 These studies suggest that the size of such a KIE may be in the range of 1. 15-1.25.…”

Section: Discussionmentioning

confidence: 97%

The Mechanism of Base-Promoted HF Elimination from 4-Fluoro-4-(4‘-nitrophenyl)butan-2-one: A Multiple Isotope Effect Study Including the Leaving Group ¹⁸F/¹⁹F KIE

Ryberg

Matsson

2001

J. Am. Chem. Soc.

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Leaving-group fluorine as well as the primary and secondary deuterium kinetic isotope effects (KIEs) have been determined for the base-promoted elimination of hydrogen fluoride from 4-fluoro-4-(4'-nitrophenyl)butan-2-one in aqueous solution. The elimination was studied for formate, acetate, and imidazole as the catalyzing base. The fluorine KIEs were determined using the accelerator-produced short-lived radionuclide (18)F in combination with natural (19)F. The (19)F substrate was labeled with (14)C in a remote position to enable radioactivity measurement of both isotopic substrates. The elimination reaction exhibits large primary deuterium KIEs: 3.2, 3.7, and 7.5 for formate, acetate, and imidazole, respectively, thus excluding the E1 mechanism. The corresponding C(4)-secondary deuterium KIEs are 1.038, 1.050 and 1.014 and the leaving group fluorine KIEs are 1.0037, 1.0047 and 1.0013, respectively. The size of the fluorine KIEs corresponds to 5-15% of the estimated maximum of 1.03 for complete C-F bond breakage. No H/D exchange is observed during the reaction. The size and trends of the KIEs for the different bases are consistent with an E1cB-like E2 or an E1cB(ip) mechanism.

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ChemInform Abstract: THE E2C MECHANISM IN ELIMINATION REACTIONS PART 7, SECONDARY KINETIC HYDROGEN ISOTOPE EFFECTS IN E2 REACTIONS OF ALICYCLICS

Cook¹,

Hutchinson²,

Parker³

1975

Chemischer Informationsdienst

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E2C mechanism in elimination reactions. VII. Secondary kinetic hydrogen isotope effects in E2 reactions of alicyclics

Cited by 7 publications

References 6 publications

Kinetic Isotope Effects and Transition State Geometries. A Theoretical Investigation of E2 Model Systems

Kinetic Isotope Effects and Transition State Geometries. A Theoretical Investigation of E2 Model Systems

The Mechanism of Base-Promoted HF Elimination from 4-Fluoro-4-(4‘-nitrophenyl)butan-2-one: A Multiple Isotope Effect Study Including the Leaving Group ¹⁸F/¹⁹F KIE

ChemInform Abstract: THE E2C MECHANISM IN ELIMINATION REACTIONS PART 7, SECONDARY KINETIC HYDROGEN ISOTOPE EFFECTS IN E2 REACTIONS OF ALICYCLICS

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E2C mechanism in elimination reactions. VII. Secondary kinetic hydrogen isotope effects in E2 reactions of alicyclics

Cited by 7 publications

References 6 publications

Kinetic Isotope Effects and Transition State Geometries. A Theoretical Investigation of E2 Model Systems

Kinetic Isotope Effects and Transition State Geometries. A Theoretical Investigation of E2 Model Systems

The Mechanism of Base-Promoted HF Elimination from 4-Fluoro-4-(4‘-nitrophenyl)butan-2-one: A Multiple Isotope Effect Study Including the Leaving Group 18F/19F KIE

ChemInform Abstract: THE E2C MECHANISM IN ELIMINATION REACTIONS PART 7, SECONDARY KINETIC HYDROGEN ISOTOPE EFFECTS IN E2 REACTIONS OF ALICYCLICS

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The Mechanism of Base-Promoted HF Elimination from 4-Fluoro-4-(4‘-nitrophenyl)butan-2-one: A Multiple Isotope Effect Study Including the Leaving Group ¹⁸F/¹⁹F KIE