T-butylammonium cation

The t-butylammonium cation forms a relatively weak complex, which was attributed to steric repulsion. The stability of anilinium complexes is about the same as that of alkylammonium complexes. The introduction of substituents at the 2- and 6-positions increases the steric repulsion which results in a drop in binding constant. This effect is enthalpic in origin. These results show that variations in the group R have only a minor effect on the stability of complexes in which the crown ether has a fully exposed cavity. Furthermore, there is no relationship between the p-K.-value of RNHJ and the stability of the complex. 

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