Nucleic acids components and their analogues. XI. Infrared spectroscopy of uracil, 8-azauracil and their derivatives in the carbonyl group stretching vibration region

Nucleic acid components and their analogues. XVI. Dissociation constants of uracil, 6-azauracil, 5-azauracil and related compounds

“…The same result was obtained on the basis of its infrared 9 and ultraviolet lO spectra. 6-Azauracil riboside shows increased acidity in a comparison to 1-methyl-6-azauracil (tipKa = 0'29) which effect may be ascribed to the polar effect of ribose.…”

Nucleic acid components and their analogues. XXVI. Ultraviolet and infrared spectra of 5-azauracil and related compounds

“…Considering their infrared spectra further analogies may be found between the compounds studied in the present work and those derived from uracil and 6-azauracil l ; e.g., the substitution with the methyl group at the 1 or 3 position in 5-azauracil (1) shifts the position of the absorption bands due to the carbonyl groups and these shifts are similar to those found in the spectra of uracil and 6-azauracil 1 .…”

“…We assume that also in the case of 5~azauracil (1) the absorption band occurring at 235 mJ.l. may be ascribed to the N -+ V transition similarly as in uracil and 6-azauracil 3 • In Table I we may follow the shifts of the absorption maximum of 5~azauracil (1) due to the introduction of the methyl group to the 1 and 3 position and further the shifts produced by ionization of the NH groups at these positions. The methyl group on the nitrogen atom at the 1 position produces a bathochromic shift of the absorption maximum whereas the methyl group at the 3 position shows almost no influence on the position of the absorption maximum (a negligible hypsochromic effect).…”

“…uracil (1) and some of its derivatives with particular regard to the detertnination of its tautomeric structure in dioxane, ethanol and neutral aqueous solutions. Since in some previous papers of this series the infrared 1 and uJtraviolet 2 spectra of uracil,.…”

“…Ultraviolet Spectra of 5-Azauracil(1) and some of its Derivatives L denotes neutral form, M mono-anion, N bis-anion; due to the instability of the measured compounds log c max values are given only to the first decimal place; E denotes 96%, Et 99·99% ethanol. The values of Amax given in parentheses belong to the product of the reaction of the compound with the employed solvent.…”