Comparative study on mid-IR and Raman spectra of chiral molecular enantiomer D- and L-xyloses

Xylose is one of the four five-carbon aldoses (molecular formula C₅O₅H₁₀), and from the perspective of molecular structure, it includes two absolute configurations: D-Xylsoe and L-Xylsoe, whose molecules are chiral enantiomers. Among them, D-Xylsoe is the second most abundant common carbohydrate, while L-Xylsoe is a rare monosaccharide. This work reports, for the first time to the best of our knowledge, a comparative study on the spectra of four aspects (between infrared spectra, between Raman spectra, between infrared and Raman spectra, and with recently published theoretical and experimental results on α-L-Xylsoe) of the high-purity solid powder D/L-Xylose enantiomers using high-precision atomic vibrational mid-infrared (mid-IR 4000-400 cm^-1) spectroscopy and Raman (4000-50 cm^-1) spectroscopy, aiming to explore whether these traditional spectroscopic methods can conveniently achieve the chiral recognition, which is very important because the structure and physicochemical properties of chiral compounds are similar, but their pharmacological and physiological effects or metabolic levels in organisms vary greatly, of this pair of enantiomers. The research results show that in the mid-IR region, it is indeed difficult to identify the chirality of this pair of enantiomers from the perspective of band frequency, relative intensity, and profile, which is consistent with most studies. However, in the far-IR region, corresponding to electromagnetic wave spectrum THz region of Raman shift, Raman scattering spectroscopy exhibits a certain degree of characteristic differences, indicating that precise traditional low-frequency Raman scattering experiments and expected far-IR/THz absorption spectra can be used as tools for the chiral recognition of this pair of molecular enantiomers.