2:2′-Biquinolyl, prepared by catalytic dehydrogenation of quinoline, has been found to give a purple colour with the cuprous ion under certain conditions. The colour reaction is sensitive, specific for copper, and the intensity of the colour produced follows Beer's law. A procedure has been worked out for the detection and estimation of copper, the smallest amount of copper detectable being 1 part in 100,000,000. Stable complexes with cupric copper and cobalt have also been prepared.

Catalytic dehydrogenation of 4-methylquinoline and 6-methylquinoline has been shown to give the corresponding dimethyl-2,2′-biquinolyls. The ultraviolet absorption spectra of the quinolines and biquinolyls have been measured, and the color reaction of the dimethylbiquinolyls with cuprous ion investigated. In all properties examined the dimethylbiquinolyls and biquinolyl behave in a parallel manner.

No abstract

Comparable ortho-substituted compounds of the biphenyl, 2-phenylpyridyl, and 2,2′-bipyridyl type have been synthesized and resolved, and the resistance to racemization determined. The results are as would have been predicted on geometrical considerations only, the compounds containing nitrogen atoms in the rings not behaving in any abnormal manner.

Several analogues of 2,2'-bipyridyl, with isoquinoline, thiazole, and pyridine rings in vario~ls combinations, have been sy~~thesized, and the effect of substituent groups in certain positions in the molecules studied with respect to their ability to react with cuprous and ferrous ion (the "cuproin" and "ferroin" reactions). The results agree with earlier work, and emphasize the desirability of two substituent groups "ortho" to the nitrogen atoms if a stable and sensitive cuprous ion reagent is wanted. The presence of one ortho substituent makes the reagent ineffective toward reaction with ferrous ion. Two of the compo~~nds synthesized had groups in positions which did not allow a coplanar cis configuration of the molecule, and only in these cases were dipicrates formed; this situation is explained by assuming that hydrogen bond formation between the nitrogen atoms is not possible.We have been engaged for some time in a study of compounds analogous t o 2,2'-bipyridyl, with respect to correlations between structure and the "ferroin" and "cuproin" reactions typical of this class of compounds. The examples we have prepared are illustrated below; to conserve space they are referred to subsequently in the text by Roman numerals.