Optically Active Amines—v

The circular dichroism (CD) curves of the N-salicylidene derivatives of some open-chain α- and β-arylalkylamines and of α,β-diphenylethylamine in ethanol, dioxan, and isooctane were measured from 450 to about 240 mμ. In comparison with similar optical rotatory dispersion (ORD) measurements reported earlier, reliable observations to shorter wavelengths with greater resolution of the individual Cotton effects were possible. Cotton effects near 315 and 255 mμ are assigned to π-π* transitions of the intramolecularly hydrogen-bonded salicylidenimino moiety, and for the α-arylalkylamine derivatives, an additional Cotton effect near 280 mμ is assigned to the π-π* transition of the aromatic ring of the parent amines. The present measurements are in agreement with the conclusion drawn earlier that there is present in these derivatives an inherently dissymmetric chromophore, arising from the interaction of the π-electrons of the aryl group and the salicylidenimino moiety. However, only some of the changes in the CD curves which occur with changes in temperature could be interpreted with the simple conformational model used earlier to indicate the steric requirements for a rotationally significant interaction of the aryl and the salicylidenimino groups.