Furanoses, “type 2” bands

It was observed (Verstraeten, 1964 1966) that 2-ketoses show type I bands at 875 cm and type IIA bands at 817 cm , regardless of whether the 2-ketoses are pyranose or furanose. These bands were ascribed to the presence of structural feature XVI and were tentatively assigned to a skeletal vibration. However, six aldoses also... 

These spectral markers make it possible to determine the relative content of each geometry in mixtures of A and B conformations. The ratio of the integrated intensities of the IR absorptions around 860 and 835 cm, A835/(/4835-i-.4860) for example, provides an estimate of the amount of B form in a sample (Liquier et ah, 1990). Similarly, the percentage of furanose rings in the north type geometry may be measured by Raman spectroscopy using the relative intensities of the 807 cm line and the band at 1100 cm (Brown et ah, 1972 Thomas and Hartman, 1973). 

Verstraeten found that only furanoses have type 2 absorption at 850 cm . He stated that his type 2 absorption is the same as the type C absorption of Barker and Stephens (1954), and to avoid confusion, it should be referred to as the latter. The type C band is displayed by both aldo- and ketofuranoses, and therefore cannot be used for distinguishing between them. 

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