T. Amyes, J. Richard
Dec 1, 1990
Citations
0
Influential Citations
41
Citations
Journal
Journal of the American Chemical Society
Abstract
The rates of reaction of 4-methoxybenzyl chloride (1), pentafluorobenzoate, and 3,5-dinitrobenzoate in 50:50 (v/v) trifluoroethanol/water are zero order in the concentration of azide ion. These reactions give good yields of the azide adduct from trapping of the 4-methoxybenzyl carbocation intermediate, and there is also strong common chloride ion inhibition of the reaction of 4-MeOArCH 2 Cl. The yields of the azide and solvent adducts give the rate constant ratio k az /k s =25 M −1 , and analysis of the chloride common ion effect gives k Cl /k s =9 M −1 , for partitioning of the carbocation intermediate. The reaction of azide ion with the carbocation intermediate serves as a diffusion-controlled «clock» for the reactions of solvent and chloride ion. There is a solvent-induced change in mechanism and in the less ionizing solvents of 80:20 (v/v) and 70:30 (v/v) acetone/water; the reaction of azide ion with 1 produces the azide adduct by both trapping of the carbocation intermediate and by a concerted bimolecular substitution reaction