Revisiting the reactions of nucleophiles with arenediazonium ions: dediazoniation of arenediazonium salts in aqueous and micellar solutions containing alkyl sulfates and alkanesufonates and ab initio analysis of the reaction pathway

摘要

Dediazoniation of 2,4,6-trimethylbenzenediazonium tetrafluoroborate, 1-ArN_2BF_4 (for the z-Ar compounds described in this paper, z refers to the length of the carbon chain of the substituent at C4 of the benzene ring), in aqueous solutions containing sodium methyl sulfate, NaMeSO_4, or sodium methanesulfonate, NaMeSO_3, yields 2,4,6-trimethylphenol. 1-ArOH, 2,4,6-trimethylphenyl methyl suflate, 1-ArOSO_3 Me and 2,4,6-trimethyl-phenyl methanesulfonate. 1-ArO_3SMe. 1-ArO_3SMe, respectively. The relative yields of 1-ArOSO_3 Me and 1-ArOH depend on the NaMeSO_4 or NaMeSO_3 concentrations, 4-n-Hexadecyl-2,6-dimethylbenzenediazonium tetrafluoroborate, 16-ArN_2BF_4, was used to determine the local head group concentration in sodium dodecyl sulfate and dodecanesulfonate micelles by chemical trapping comparing the relative product yields with those obtained in water using the short chian analogs. Ab initio calculations of the spontaneous dediazoniation of phenyldiazonium ion in the gas phase, as well as in aqueous solution with, or without, aded MeSO_3~, yield potential energy surfaces for the reaction. For this model the calculated and dxperimental values of the spontaneous dediazoniation rate constants in aqueous solution, as well as the product composition, were similar to those obtained wiht 1-ArN_2~+. These results suggest that in aqueous solution nucleophiles can only compete with water if a diazonium ion nucleophile complex is formed prior to N_2 loss. Calculations show that the addition of nucleophiles to the arenediazonium ion occurs without a saddle point in the potential energy surface, suggesting that the free phenyl cation is not an obligatory intermediate in aqueous solutions.