Solvent effect on the dissociation of m- nitroanilinium ion in water-ethylene glycol media at 25°C
1983; Elsevier BV; Volume: 28; Issue: 11 Linguagem: Inglês
10.1016/0013-4686(83)85229-3
ISSN1873-3859
Autores Tópico(s)Surfactants and Colloidal Systems
ResumoThe dissociation constants (sK)BH+ of m-nitroanilinium ion, have been determined at 25°C in aqueous mixtures of 10, 30, 50, 70 and 90 wt.% of ethylene glycol from spectrophotometric measurements. The solvent effect on the dissociation behaviour of this acid: Δ0t(BH+ −B)sys = 2.303 RT [p(sK)NBH+ −p(wK)NBH+] in these media results in a characteristic minimum with change in the solvent composition. The solvent effect has been discussed in terms of the free energies of transfer (ΔG0t) from water to the aqueous glycol solvents, of the uncharged base (B) evaluated from measured solubilities, of the hydrochloride of the base (BHCl) computed from the corresponding values for HCl, and also of the individual ions assessed from the previous knowledge of ΔG0t(Cl−). The corresponding data for the protonated Tris (hydroxymethyl) methylamine (Tris H+) and p-nitroanilinium ion in the same solvent mixtures obtained from the literature are also compared. Solvent effect on the dissociation of m-nitroanilinium ion has been found to be nearly the same as that for the p-nitroanilinium ion with similar chemical composition but different from that observed in the case of Tris H+ of different chemical nature.
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