Formation and stability of the 4-methoxyphenonium ion in aqueous solution.

The reaction of 2-methoxyphenylethyl tosylate (MeO-1-Ts) is first-order in [N(3)(-)]. A carbon-13 NMR analysis of the products of the reactions of MeO-1-[α-(13)C]Ts shows the formation of MeO-1-[β-(13)C]OH and MeO-1-[β-(13)C]N(3) from the trapping of a symmetrical 4-methoxyphenonium ion reaction intermediate 2(+). An analysis of the rate and product data provides a value of k(az)/k(s) = 83 M(-1) for partitioning of 2(+) between addition of azide ion and solvent. These data set a limit for the lifetime of 2(+) in aqueous solution.