Carbonyl stretching vibrations of uracil studied by 18O isotopic substitutions with UV resonance Raman spectroscopy

Resonance Raman spectra of uracil and its 18O isotopically substituted species (in positions 2-, 4- and 2,4-) have been obtained in neutral aqueous solutions with 257 nm excitation. A computer decomposition of the 1560-1740 cm−1 region showed the presence of five bands in this region, at 1629, 1659, 1673, 1689 and 1706 cm−1 in the case of uracil. The shifts and intensity variations caused by isotopic substitution are also reported, and these help precise assignments of these bands. The discussion also takes into account the resonance Raman spectra of 2- and 4-thiouracil and 2,4-dithiouracil, obtained with 300 nm excitation.

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