The o+ o+;=±i+ i+ equilibrium has been detected in all amines in Table I, and in some cases crystalline isomers of both configurations have been isolated. For example, in the solid state the bishydrochloride of [8.8. 8J-II exists as the o+ o+ isomer, whereas the bis-bifluoride is z+ z+. Evidently the o+ i+ isomers are of higher free energy than o+ o+ or i+ i+, probably because of torsional and nonbonded repulsion effects. The o+ i+ ion is detected only when k= 1= m> 10, and then as a fleeting intermediate during establishment of the equilibrium.

Equilibrium constants (o+ o+ z'+ z'+) for the amines in 50% TFA are given in TableI, and hydrophobic bonding is thought to be important in determining the position of the equilibrium in aqueous media. An alternation effect is evidentin the symmetricalions; even chain lengths favor i+ i+ isomers and odd, o+ o+ isomers. The z'+ z'+-[8.8. 8] ion is particularly stable, and models suggest that it has a beautifully compact structure in which the chains contain a maximum of trans arrange-ments and are oriented for favorable nonbonded and dispersion interactions. It is thought that the o+ o+ and