oxonium

That is associated with Si[0.sub.2] particles and either bulk water, [([H.sub.2]0).sub.n], or highly hydrated oxonium ions, [H.sub.3][0.sup.+][([H.sub.2]0).sub.n][25, 27].

Monomeric anthocyanins undergo a reversible structural transformation as a function of pH (colored oxonium form at pH 1.0 and colorless hemiketal form at pH 4.5).

Removal efficiency in pH=2 (Fig.3) compared to other pH had less amount that may be due to generated oxonium ion [H3O2]+ [29] In addition, the scavenging effect of hydroxyl radicals by hydrogen ions becomes important at a very low pH .

Initiators of stable organic salts can be divided into several differenl categories: carbenium salts, oxacarbe- nium salts, carboxonium salts, oxonium salts, etc.

Five oxonium tetrahalogenaurate(III) (Hal = Cl, Br) benzo-crown ether (BCE) complexes (Table 2, Compound 12a and 12b) are prepared and reported by Pluzhnik-Gladyr and coworkers [56].

The P450-dependent hydroxylation of the methoxy group yields an intermediate corresponding to the hemiacetal of formaldehyde that can cyclize to form a methylenedioxy bridge via an ionic mechanism involving the methylene oxonium ion intermediate.

This finding could be explained by the fact that the oxonium ion ([H.sub.3][O.sup.+.sub.2]) can enhance the stability of [H.sub.2][O.sub.2] (8) [39].

Rutin and other flavonoids are highly coloured in the acidic medium due to formation of oxonium salts.

The protonic acid evolved, [HSbF.sub.6], is highly reactive toward oxygen-based heterocyclic monomers and will thus initiate the ring opening polymerization of epoxides through the propagating oxonium ion:

Neighboring group participation of the oxygen can cause an opening of the bromonium ion intermediate thereby giving rise to an oxonium ion.

The proton is first bound to the anhydride molecule under generation of an oxonium cation, which then reacts with alcohol and monoester originates (Ernest et al., 1959).