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

Abstract

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.

Benzylic Phosphates as Electrophiles in the Palladium-Catalyzed Asymmetric Benzylation of Azlactones

“…Electron-rich benzyl electrophiles are more reactive, requiring a less labile leaving group. Increased electron density would stabilize the transition state in an S N 2 reaction, leading to charged intermediates . On the other hand, low-valent palladium would better coordinate to an electron-poor π system, which should have led to increased reactivity.…”

Organocatalytic Activity of Cinchona Alkaloids: Which Nitrogen Is More Nucleophilic?

“…In all cases, pseudo-first-order conditions were employed with the amines 1 in high excess. As a consequence of the previously reported proportionality between salt concentration and conductance in acetonitrile, the formation of the ammonium salts gave rise to an exponential increase of the conductances G (eq ) . The second-order rate constants (Table ) were obtained from plots of k obs versus [ 1 ]. normald G / normald t -1pt = G max false( 1 − 1.5pt normale − k obs t false) 1.5pt + 1.5pt C …”

Stereoelectronic effects in Menshutkin‐type SN2 reactions: theoretical study based on through‐space/bond orbital interaction analysis

“…The substituent effects on the reaction rates have been numerously investigated by experimental and theoretical approaches . Kim et al .…”

“…Kim et al . investigated the substituent effects both on nucleophile and electron‐deficient electrophilic center of Menshutkin reactions to compare the evidence for the duality of S N 1 and S N 2 mechanisms . Westaway presented the substituent effects on the S N 2 transition states (T‐Ss) by using chlorine leaving group and nucleophile carbon kinetic isotope effects.…”