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

Table 5

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

Assignment	Nitrobarbituric (cm^−1)	Cocrystal (cm^−1)	Quinine (cm^−1)	Assignment
Carbonyl out-of-plane bending mode	779	791
C–N ring deformation mode	1246	1234
		1364	1371	Nonprotonated quinuclidine mode
Nitro group symmetric stretching mode	1381	1359
		1575	1576	Nonprotonated quinoline mode
2-CO stretching mode	1614	1620
4,6-CO antisymmetric mode	1651	1661
4,6-CO symmetric mode	1705	1691