Substituent dependence of the selectivity in alkene bromination through bromocarbenium ions

Bienvenüe-Goetz, E.; Dubois, Jessica

doi:10.1021/ja00408a019

Cited by 10 publications

(5 citation statements)

References 2 publications

(2 reference statements)

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“…These differences have been attributed to variations in transition-state positions [12]: a reactivity change significantly shifts the transition state in bromination but not in hydration. This is supported by the following general proposal [19]: bromination of olefins XRC=CH 2 , where X is a conjugatively electron-donating group, goes through a carbenium-ion-like transition state in contrast to the bromonium ion-like transition states when substituents are not able to donate electrons by resonance. This interpretation The absence of linearity could arise from a change in the transition-state charge distribution from bromonium to carbenium-ion-like.…”

Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 79%

“…Larger o:-M//3-M values for vinyl bromide and styrene imply a carbocationic charge distribution. This is supported by the following general proposal [19]: bromination of olefins XRC=CH 2 , where X is a conjugatively electron-donating group, goes through a carbenium-ion-like transition state in contrast to the bromonium ion-like transition states when substituents are not able to donate electrons by resonance. The small o:-M//3-M ratios for enol acetate and ether appear to contradict this rule.…”

Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 79%

“…Discrepancies between the selectivities of these reactions are not unexpected. (i) Reactivities of hydration are roughly described [11] by a p+a+ relationship but a similar description of brornination rates is obtained only if interactive terms are included in the reactivity-structure correlation [19]. Accordingly, the log kBri/log k H 30 + plot is a curve (Fig.…”

Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 86%

“…(i) Reactivities of hydration are roughly described [11] by a p+a+ relationship but a similar description of brornination rates is obtained only if interactive terms are included in the reactivity-structure correlation [19]. (i) Reactivities of hydration are roughly described [11] by a p+a+ relationship but a similar description of brornination rates is obtained only if interactive terms are included in the reactivity-structure correlation [19].…”

Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 99%

“…To discuss the results in terms of reactivity-selectivity dependence, indices of transitionstate position have also been measured. 416 tion is justified by the finding that bromination transition states ofolefins, GROIC = CR/3R/3', are carbenium ionlike when G is a strongly electron-donating substituent [19] .…”

Section: Introductionmentioning

confidence: 99%

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Electrophilic Additions to Highly Reactive Enol Ethers. The Particular Role of Resonance in Determining the Kinetic Selectivity Evidenced by Extensive Comparison of Olefin Bromination and Hydration

Ruasse¹

1985

Israel Journal of Chemistry

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The kinetic selectivity of aliphatic enol ethers, EtOCR = CHR' (R and R′ = H or Me), towards electrophiles, I2, Br2 and H3O+, is expressed by the kinetic effect of a methyl substituent in the α position with respect to the ethoxy group, kα‐Me/kH. As expected from the reactivity–selectivity principle, RSP, these selectivities are small, 16, 18 and 330, respectively, as compared to those observed for less reactive olefins. However, a more general comparison of the selectivities of various XCH = CH2 olefins (X = Br, Me, Ph, OAc, OEt) reveals anomalies in their behavior with respect to the RSP: (i) enol ether iodination and bromination exhibit the same selectivity although their rates differ by 4 powers of ten, (ii) enol acetate and enol ether show similar selectivities in bromination but the rate of acetate is 3 × 105 times smaller than that of ether and (iii) in hydration the selectivities of these two olefins are similar to that of styrene although rates range over 7 powers of ten from styrene to enol ether. In contrast with what was previously observed for homogeneous series of R‐substituted styrenes (Ph(R)C = CH2), there is no reactivity–selectivity relationship for electrophilic additions to XCH = CH2 olefins. There is a parallelism, however, between the selectivities and the transition‐state position estimated by the Brønsted exponents for hydration and by the Winstein–Grunwald coefficients for solvent effects on halogenations. These results are discussed in terms of different resonance effects on transition states and on reactivities which could arise from differences in the relative contributions of thermodynamic and intrinsic kinetic (Hammond effects) factors on the selectivities.

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Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 79%

Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 79%

Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 86%

Section: Absence Of Similarity In the Reactivity -Selectivity Dependementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Electrophilic Additions to Highly Reactive Enol Ethers. The Particular Role of Resonance in Determining the Kinetic Selectivity Evidenced by Extensive Comparison of Olefin Bromination and Hydration

Ruasse¹

1985

Israel Journal of Chemistry

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Formation of Carbon–Halogen Bonds (Cl,Br,I)

Sasson

2009

Patai's Chemistry of Functional Groups

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Introduction Halogenation in Presence of Solid Supports or Catalysts Halogen Exchange and Transhalogenation Reactions Oxyhalogenations Cohalogenation and Mixed Halogenation Halogen–Halogen Reagents Carbon–Halogen Reagents Nitrogen–Halogen and Phosphorus–Halogen Reagents Oxygen–Halogen Reagents Sulfur–Halogen Reagents Silicon–Halogen Reagents Halogenation with Metal Halides and Halodemetallation Halogenation in Special Environments Carbon–Halogen Bond Formation by Extrusion of CO , CO 2 or SO 2 Ring Opening of Oxiranes

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ChemInform Abstract: SUBSTITUENT DEPENDENCE OF THE SELECTIVITY IN ALKENE BROMINATION THROUGH BROMOCARBENIUM IONS

Bienvenüe-Goetz¹,

Dubois²

1981

Chemischer Informationsdienst

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Substituent dependence of the selectivity in alkene bromination through bromocarbenium ions

Cited by 10 publications

References 2 publications

Electrophilic Additions to Highly Reactive Enol Ethers. The Particular Role of Resonance in Determining the Kinetic Selectivity Evidenced by Extensive Comparison of Olefin Bromination and Hydration

Electrophilic Additions to Highly Reactive Enol Ethers. The Particular Role of Resonance in Determining the Kinetic Selectivity Evidenced by Extensive Comparison of Olefin Bromination and Hydration

Formation of Carbon–Halogen Bonds (Cl,Br,I)

ChemInform Abstract: SUBSTITUENT DEPENDENCE OF THE SELECTIVITY IN ALKENE BROMINATION THROUGH BROMOCARBENIUM IONS

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