Studies of intermolecular interactions by relaxation times in solution

3 Studies of intermolecular interactions by relaxation times in solution 

T-[ and T2 are strongly dependent on the electron distribution around the nucleus and on the intra- and intermolecular interactions that can modify the electron distribution, such as  

The study of 33S relaxation times and line widths has provided much information about dynamic behaviour and molecular association for sulpholane, sulphonic acids and sulphonate anions. It is interesting to observe that in all cases, 33S is an internal nucleus and is particularly sensitive to solvent and association effects, even though it is not directly exposed to these interactions. 

The same authors26 have also studied the effect of pH on the 33S line width of a solution of Na2S04. In the pH range 0.9-6.4, the overall line width change is 190 Hz, and the chemical shift variation is 3 ppm. The origin of these variations is not due to exchange phenomena but probably to the interaction of the unprotonated species with sodium ions. Ion pairs should relax faster than not complexed species. 

The same model can be applied to methane- and trifluoromethanesulphonic acids.93 Also in these two cases, there is a linear dependence of 33S Ti on concentration in very large ranges (approximately 0.1-8 M for methanesulphonic acid and 0.1-5 M for trifluoromethanesulphonic acid). Moreover, Ti in methane-sulfonic acid increases linearly with the degree of ionization of the acid. In both cases, 170 Ti has a parallel behaviour. For methanesulphonic acid, T] at infinite dilution is 11.6 ms at 293 K and 13.5 ms at 313 K. For trifluoromethanesulphonic 

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