Multiple structure–reactivity relationships for a Menschutkin-type S<sub>N</sub>2 reaction

Yoh, Soo-Dong; Tsuno, Yuho; Fujio, Mizue; Sawada, Masami; Yukawa, Yasuhide

doi:10.1039/p29890000007

Cited by 18 publications

(10 citation statements)

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“…This is in complete agreement with the result of previous work. 7,8,13 In the case of the present benzyl system, the better leaving groups thus do not yield a 'product-like' transition state but rather a 'loose' one. This result agrees with the prediction of the More O'Ferrall diagram for the effects of leaving group variation in an S N 2 transition state.…”

Section: Resultsmentioning

confidence: 83%

Quantitative approach to the Menschutkin reaction of benzylic systems

Yoh

Cheong

Lee

2002

J of Physical Organic Chem

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The quaternization reactions of substituted (Z)-benzyl (X)-benzenesulfonates with substituted (Y)pyridines were investigated in acetonitrile at 35°C. The magnitudes of the Hammett reaction constants r X , r Y and r Z indicate that a stronger nucleophile leads to a lesser degree of bond breaking. In addition, a better leaving group is accompanied by a lesser degree of bond formation. Application of multi-Hammett interactions, j YZ j >j XY j >j XZ j, predicts that these Menschutkin-type reactions are dissociative S N 2 reactions. In particular, the reaction of strongly activated benzyl derivatives with tertiary amines in acetonitrile reveals a more advanced bond breaking like S N 1 reactions. The predicted mechanism for the benzylation of pyridines with benzylic systems is evident from More O'Ferrall-Jencks diagram and the semi-empirical MO calculations with the AM1 method.

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Section: Resultsmentioning

confidence: 83%

Quantitative approach to the Menschutkin reaction of benzylic systems

Yoh

Cheong

Lee

2002

J of Physical Organic Chem

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“…p ‐Cl BnOTs, and m ‐CN BnOTs were prepared in a similar manner. The identity of the products were confirmed by 1 H (300 MHz) and 13 C (75 MHz) NMR spectroscopies, and HRMS analyses and their melting point were compared with the literature values 34…”

Section: Methodsmentioning

confidence: 99%

Reversed Electron Apportionment in Mesolytic Cleavage: The Reduction of Benzyl Halides by SmI₂

Yitzhaki

Hoz

2015

Chemistry A European J

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The paradigm that the cleavage of the radical anion of benzyl halides occurs in such a way that the negative charge ends up on the departing halide leaving behind a benzyl radical is well rooted in chemistry. By studying the kinetics of the reaction of substituted benzylbromides and chlorides with SmI2 in THF it was found that substrates para-substituted with electron-withdrawing groups (CN and CO2 Me), which are capable of forming hydrogen bonds with a proton donor and coordinating to samarium cation, react in a reversed electron apportionment mode. Namely, the halide departs as a radical. This conclusion is based on the found convex Hammett plots, element effects, proton donor effects, and the effect of tosylate (OTs) as a leaving group. The latter does not tend to tolerate radical character on the oxygen atom. In the presence of a proton donor, the tolyl derivatives were the sole product, whereas in its absence, the coupling dimer was obtained by a SN 2 reaction of the benzyl anion on the neutral substrate. The data also suggest that for the para-CN and CO2 Me derivatives in the presence of a proton donor, the first electron transfer is coupled with the proton transfer.

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“…The reaction rates of 0.0005 M Z-substituted benzyl tosylates with 0.01 to 0.3 M Y-substituted N,N-dimethylanilines were measured in acetonitrile at 35°C by following the increase in conductance of the quaternary anilinium salts produced. 10,11 The precision of the fit to pseudo-first-order kinetics was generally satisfactory, with correlation coefficients b 0.99995 over 2.5 halflives of the reaction.…”

Section: Resultsmentioning

confidence: 88%

“…4 and the carbocationic character of the k 2 process at the most activated end is still far from that of the S N 1 transition state. 10,11 Nevertheless, it should be noted that the r value for the bimolecular process is still close to that for the unimolecular process, which should be characteristic of the intermediate carbocation. The mechanism of the bimolecular Menschutkin reaction will be discussed in more detail in a forthcoming paper.…”

Section: Methodsmentioning

confidence: 90%

“…[2][3][4][5] Mechanistic studies on the Menschutkin reaction of benzylic systems mostly led to the conclusion that the reaction proceeds by a typical S N 2 mechanism with a concerted displacement transition state. [6][7][8][9] In previous papers, 10,11 we discussed the mechanism of the Menschutkin reaction of Z-substituted benzyl tosylates with Y-substituted N,N-dimethylanilines in acetone or acetonitrile based on the substituent effect analysis. Electron-donating Z-substituents enhance the reaction, indicating an appreciable development of positive charge at the benzylic reaction center in the transition state.…”

Section: Introductionmentioning

confidence: 99%

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The Menschutkin reaction of benzyl p‐toluenesulfonates with N,N‐dimethylanilines. Evidence for the duality of SN1 and SN2 mechanisms

Kim¹,

Yoh²,

Lim³

et al. 1998

J. Phys. Org. Chem.

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The rate data for the Menschutkin reaction between strongly activated Z-substituted benzyl ptoluenesulfonates and Y-substituted N,N-dimethylanilines in acetonitrile at 35°C fit the equation, k obs = k 1 k 2 [DMA], which is consistent with concurrent first-and second-order processes. The k 1 and k 2 values for each substrate were separated based on the above equation. The S N 1 rate constant, k 1 , is unaffected by the nature of the nucleophile, whereas the S N 2 rate constant, k 2 , increased with the electron-donating substituent of the N,N-dimethylaniline. The substituent effect on the k 1 values is linearly correlated by the Yukawa-Tsuno equation with r = À5.2 and r = 1.3. The unimolecular reaction can be regarded as a classical S N 1 mechanism. In contrast, that on the k 2 values shows an upward curvature when analyzed by the Brown ' treatment. These results are ascribed to the simultaneous and independent occurrence of S N 1 and S N 2 mechanisms in the present Menschutkin reaction.

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Multiple structure–reactivity relationships for a Menschutkin-type S_N2 reaction

Cited by 18 publications

References 1 publication

Quantitative approach to the Menschutkin reaction of benzylic systems

Quantitative approach to the Menschutkin reaction of benzylic systems

Reversed Electron Apportionment in Mesolytic Cleavage: The Reduction of Benzyl Halides by SmI₂

The Menschutkin reaction of benzyl p‐toluenesulfonates with N,N‐dimethylanilines. Evidence for the duality of SN1 and SN2 mechanisms

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Multiple structure–reactivity relationships for a Menschutkin-type SN2 reaction

Cited by 18 publications

References 1 publication

Quantitative approach to the Menschutkin reaction of benzylic systems

Quantitative approach to the Menschutkin reaction of benzylic systems

Reversed Electron Apportionment in Mesolytic Cleavage: The Reduction of Benzyl Halides by SmI2

The Menschutkin reaction of benzyl p‐toluenesulfonates with N,N‐dimethylanilines. Evidence for the duality of SN1 and SN2 mechanisms

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Product

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Multiple structure–reactivity relationships for a Menschutkin-type S_N2 reaction

Reversed Electron Apportionment in Mesolytic Cleavage: The Reduction of Benzyl Halides by SmI₂