The Isolation of Oxamide and Parabanic Acid from the Products of Ultraviolet Irradiated Uracil

Conrad, Walter E.

doi:10.2307/3570219

Cited by 13 publications

(1 citation statement)

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“…Photolysis (110) of uracil in aqueous or frozen solution reversibly forms a dimer (111) and a hydration product (112,117) (incidentally, uracil does not form a stable chemiadsorbed hydrate (113). In aerated aqueous solution urea (114), parabanic acid, and oxamide have been detected. The stereochemistry of the dimer has been established by degradation studies.…”

Section: Ac2omentioning

confidence: 99%

Uracil. A Perspective

Pasquale¹

1978

Ind. Eng. Chem. Prod. Res. Dev.

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The RNA component, uracil, is reviewed from structural, spectroscopic, synthetic, chemical reactivity, biochemical, and application viewpoints. This fascinating molecule undergoes a plethora of reactions at nine different sites; the specificity of these is considered in some detail. The review contains 189 literature citations.Uracil, a major component of nucleic acid, has aroused the interest of numerous experimentalists. The properties and reactions of this molecule gain significance when one considers their relationship to the chemical modification of biologically active nucleic acids and, consequently, living organisms. An understanding of this interplay simultaneously nourishes biomedical applications and instills the awareness of potential hazards. This report highlights the properties and chemistry of uracil with the intention of hopefully stimulating future applications. PropertiesUracil [2,4(lH,3H)-pyrimidinedione, C4H4N202], a white crystalline solid, melts with decomposition at 335-338 °C. This pyrimidine derivative is essentially insoluble in cold water (pH 7) and typical organic solvents. It dissolves in boiling water (ca. 2 g/100 mL) and dipolar aprotic solvents, e.g., Me2SO (1) (5.6 g/100 mL at 23 °C). Due to its amphoteric nature it is soluble in acids, i.e., 35% H2S04 (ca. 1.5 g/100 mL at 25 °C), CF3C02H (2), HF (3), and bases. With regard to its weakly basic properties uracil has been used as an indicator to extend the acidity function Ha (4) up to 17% by weight S03 in H2S04, As acidity increases, uracil first protonates at the more basic site (0 at C4), then doubly protonates (0 at C4 and C2). In basic solution uracil behaves as a weak dibasic (5) acid with ionization first at N3 (pKa = 9.7) and then at N4 (pKa = 14.2), The ability of nucleic acid bases, including uracil, to associate by hydrogen bonding ( 6) is essential to their role in biological evolution. StructureAfter considerable difficulty, a single crystal of uracil was obtained (twinning is prevalent) and analyzed (7) by X-ray crystallography. The space group is P24/a; there are four molecules in the unit cell which are essentially parallel and held together by NH-0 hydrogen bonds. The molecule is planar in the solid state with the two sets of C-C and C-0 bonds being of similar length and exists in its lactam form.

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Section: Ac2omentioning

confidence: 99%