THE CORRELATION OF ULTRAVIOLET AND INFRARED SPECTRA IN THE ELUCIDATION OF STRUCTURE OF SOME PYRIMIDINES$^{\ast}$

Author Institution: Siena Heights CollegeAn empirical comparison of the infrared and ultraviolet spectra of a series of isomeric aminopyrimidines with the corresponding hydrochlorides has been made. Although the vibrational spectra are too complex for detailed analysis, the effect of hydrochloride formation on the spectrum enables correlations with probable structures to be drawn. This is particularly helpful since the compounds investigated may exhibit tautomerism between the keto-enol and/or the aminoimino structures which might influence the metabolism of the natural occurring compounds of this type. The effect of ring substituents in modifying the spectral response to hydrochloride formation is very striking in the series: $$2-NH_{2}-pyrimidine, 2-NH_{2}-6-Cl-pyrimidine, 2-NH_{2}-OH-pyrimidine.$$ In the last case the strong HCl band at $3.62 \mu$ does not occur, although it is clear in the isomeric compound. This anomolous behavior is reflected in the ultraviolet absorption. The effect of ring position on the response to hydrochloride formation is also seen in a comparison of $2-NH_{2}-6-Cl$-pyrimidine and $2-Cl-6-NH_{2}-pyrimidine$. The C-Cl vibration and its overtone at $6.5 \mu$ are markedly depressed in the former, whereas the corresponding bands are strengthened in the case of its isomer