Nuclear magnetic resonance and quadrupole resonance studies of triethylamine dihydrochloride

Abstract

35 Cl quadrupole resonance and 1H magnetic resonance studies of the adduct NEt3· 2HCl show its structure to be [NEt3H]+HCl–2 in the crystalline solid and in solutions in chloroform. In both phases, the dichloride ion appears to be asymmetric, so that the limiting proton chemical shift in solution is close to 10 p.p.m., compared to values of 14 p.p.m. for the symmetric ion. The factor which stabilizes the asymmetric configuration is believed to be hydrogen-bonding to the cation of the type [NEt3H]+…ClHCl–. It is proposed that the close approach of any positively-charged species along directions close to that of the Cl…Cl axis will stabilize the asymmetric ion; otherwise the ion will tend to be symmetrical, or at least will appear to be so within the time-scale of these experiments. The potential well for proton motion in the dichloride ion appears therefore to be relatively broad, unlike that in HF–2.