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

✍ Scribed by Sung Hong Kim; Soo-Dong Yoh; Chultack Lim; Masaaki Mishima; Mizue Fujio; Yuho Tsuno

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 151 KB
• Volume: 11
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199804)11:4<254::aid-poc2>3.0.co;2-6

✦ Synopsis

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,

, 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.