Abstract
The interactions of organic cations, such as alkylamine hydrochlorides, RNH+3Cl-(R=CH3, C2H5, C3H7, C4H9) and tetraalkylammonium bromides, R4N+Br- (R=C2H5, C3H7, C4H9) with an organic anion, 2, 7-naphthalenedisulfonic acid (NDS) in aqueous solutions have been studied by using nmr spectroscopy. For comparison, the interactions of aliphatic alcohols (ROH, R=C2H5, C3H7, C4H9) with NDS were studied.
The chemical shifts of aliphatic protons of such compounds in the presence of NDS were displaced to higher field (relative to external TMS). The large upfield shifts can be explained by the proximity of the aliphatic moieties to the anisotropic aromatic in aqueous solutions. In this paper were listed the shifts, Δδ, observed for alcohols, alkylamine hydrochlorides and tetraalkylammonium bromides (1 mol/l) when the medium was changed from pure water to NDS aqueous solutions (1 and 1.5 mol/l).
The results obtained are as follows:
(1) Alcohols. The shifts, Δδ, increased with increasing the length of the alkyl chains. Methyl and methylene proton signals were shifted to about the same extent.
(2) Alkylamine hydrochlorides. The shifts increased with increasing the length of the alkyl chains. The methyl proton singals were shifted more than the methylene protons.
(3) Tetraalkylammonium bromides. The shifts decreased with increasing the length of the alkyl chains. The methylene proton signals were shifted more than the methyl protons.
From the above results the spatial mode of the interaction between the organic ions in aqueous solutions was discussed.
