Nonlinear Taft Polar Free Energy Relationship: Reactions of N-Substituted Benzyl Amines with Benzyl Bromide in Methanol
Article first published online: 31 AUG 2013
© 2013 Wiley Periodicals, Inc.
International Journal of Chemical Kinetics
Volume 45, Issue 12, pages 803–810, December 2013
How to Cite
Ravi, R., Sanjeev, R. and Jagannadham, V. (2013), Nonlinear Taft Polar Free Energy Relationship: Reactions of N-Substituted Benzyl Amines with Benzyl Bromide in Methanol. Int. J. Chem. Kinet., 45: 803–810. doi: 10.1002/kin.20818
- Issue published online: 24 OCT 2013
- Article first published online: 31 AUG 2013
- Manuscript Accepted: 7 AUG 2013
- Manuscript Revised: 2 AUG 2013
- Manuscript Received: 23 APR 2013
The rates of reactions of N-substituted benzyl amines with benzyl bromide were measured using a conductivity technique in methanol medium. The reaction followed a total second-order path. The end product of the reaction is identified as dibenzyl alkyl amine (C6H5CH2N(R)CH2C6H5). The rates increased with a decrease in the electron-donating capacity or with an increase in the Taft σ* value of electron-donating alkyl substituents (R) such as t-butyl (σ* = −0.3), i-propyl (σ* = −0.19), n-butyl (σ* = −0.13), and ethyl (σ* = −0.1) on nitrogen of the amine until the Taft σ* value becomes zero for the methyl group ( = 0.00), and then the rates decreased with an increase in the electron-withdrawing capacity or with an increase in the Taft σ* value of electron-withdrawing substituents (R) such H and C6H5 ( = 0.49 and = 0.6). The locus of the Taft polar free energy relationship has a maximum near the point for N-methyl benzyl amine, showing that there is a sharp change in the rate-determining step. A mechanism involving formation of an SN2-type transition state between the amine nucleophiles and the benzyl bromide and its subsequent decomposition is proposed. Activation parameters were calculated and are discussed.