This is the first comparative analysis of the IR and Raman spectra
of whewellite, weddellite and caoxite, which provides a quick
and reliable identification protocol among Ca-oxalates.
In this work, a new synthesis procedure of COT is described as a
valid alternative to the others proposed in the literature. However,
the synthesis is difficult and it is hard to obtain single crystals for
structural determination. The crystalline structure of COT obtained
in this study is virtually identical to that reported by Basso et al. [3]
and Deganello et al. [18]. To the best of our knowledge, the Raman
spectrum of COT is reported in this paper for the first time. Both
FTIR and Raman spectra of COT have been here described. A comparison
of the vibrational spectra of the three forms of calcium
oxalates clearly shows that the perturbation of the oxalate group
by the net of hydrogen-bonded H2O molecules is negligible.
The complex H-bonding network of COT has been discussed,
bridging crystallographic and spectroscopic data, and showing a
complex net of H-bonding interactions. The infrared and Raman
active transition frequencies appear being can be correlated with
the lengths (strengths) of the hydrogen bonds.