The solvent effect and the structural effect of halides on the quaternization Et3N+RX→Et3RNX

In this study, the solvent effect on the rate constant of the quaternization Et 3 N+BzCl→Et 3 BzNCl was studied. The used 20 solvents are, respectively, protic aliphatics, aprotic aliphatics, protic aromatics, and aprotic aromatics. The rate constant at 50 °C ranges from 0.23×10 −5 M −1 s −1 in benzene to 31.74×10 −5 M −1 s −1 in DMSO. For the solvents which possess normal characteristics among dipole moment ( μ ), solubility parameter ( δ ), and dielectric constant ( e ), ln  k is shown to be proportional to δ . The activation energy ( E a ), Gibbs free energy (Δ G ≠ ), entropy (Δ S ≠ ), and enthalpy (Δ H ≠ ) in the various solvents were also obtained, and E a −Δ H ≠ = RT was proved. On the other hand, the structural effect of the halides on the rate constants of the quarternization Et 3 N+RX→Et 3 RNX is shown by the two sequences k( RI ) / k( BuI )=2193, 1170, 522, 5.3, 1.3, 1.1, and 1 when R=Bz, Me, allyl, Et, Pr, and Hex, respectively, where k( BuI )=3.37×10 −5 M −1 s −1 in acetonitrile at 30 °C; and k (BzI): k (BzBr): k (BzCl)=2200:243:1, where k( BzCl )=3.36×10 −5 M −1 s −1 in the same solvent and at the same temperature.