Vibrational Spectroscopic Study of the Cocrystal Products Formed by Cinchona Alkaloids with 5-Nitrobarbituric Acid

Table 1

Assignments of the major bands in the fingerprint region of the infrared absorption spectra of 5-nitrobarbituric acid, cinchonine, and their 1 : 1 cocrystal product.

Assignment	Nitrobarbituric (cm^−1)	Cocrystal (cm^−1)	Cinchonine (cm^−1)	Assignment
Carbonyl out-of-plane bending mode	779	756
C–N ring deformation mode	1246	1286
		Obscured and not observed	1360	Nonprotonated quinuclidine mode
Nitro group symmetric stretching mode	1381	1377
		Obscured and not observed	1566	Nonprotonated quinoline mode
2-CO stretching mode	1614	1622
4,6-CO antisymmetric mode	1651	Not observed
4,6-CO symmetric mode	1705	1701