The sonolysis of cytosine and thymine

Sonolysis of cytosine has been studied at 630 kHz in the presence of air and nitrogen. The degradation products were identified by gas chromatographic – mass spectral analysis. Under aerated conditions the following products were found: urea, formyl urea, parabanic acid, isobarbituric acid, oxaluric acid, alloxan monohydrate, alloxantin, dialuric acid, and uracil glycols. Under nitrogen the degradation products were isobarbituric acid, alloxan monohydrate, and uracil glycols. The observed products have been used to develop a possible mechanism for the sonolytic degradation. There appears to be some similarity with the products reported from radiolysis studies of this compound. Sonolysis of thymine in the presence of air was reinvestigated and the gc–ms analysis shows that a previously reported, unidentified, product may be 5-hydroxy-5-methylbarbituric acid.

The sonolysis of uracil

The sonolysis of uracil (1) has been studied at 630 kHz in the presence of air, oxygen, nitrogen, and argon. The degradation products were identified by gc–ms analysis. Under aerated conditions the following products were found: uracil glycols (7), isobarbituric acid (8), N-formyl-N′-glyoxylurea (6), 5-hydroxyhydantoin (9), dialuric acid (10), alloxan monohydrate (12), parabanic acid (13), and oxaluric acid (14). In deaerated solutions 6, 13, and 14 were not observed but either 6-hydroxy-5,6-dihydrouracil(17) or its isomer (18) were detected in addition to 7, 8, 9, 10, and 12. The observed products have been used to develop a possible mechanism for the sonolytic degradation and the results are similar to those obtained in radiolysis.The sonolytic degradation of 5-bromouracil (19) is also reported; the products observed were 5-bromobarbituric acid (20), 12, 13, 14, and 9 and these can be rationalized by a similar mechanistic scheme.

Identification of Radiolysis Products of Cytosine Resulting from the Deamination Pathway

Radiolysis products resulting from the deamination pathway were isolated and identified after irradiation of cytosine by gamma rays in neutral aqueous solutions. They were identical to those identified in uracil radiolysis i. e. 5,6-dihydroxy-5,6-dihydro-uracil (cis and trans forms), iso-dialuric acid, alloxan, 5-hydroxy-hydantoin, parabanic acid and oxaluric acid. The absence of 4,4′-di-iso-barbituric acid, alloxantin or iso-barbituric acid could be explained by the good stability of uracil glycols. The identification of buiret proof of potential degradation mechanisms different from these involving of the free radical attack on the 5,6 double bond. Gamma Irradiation of Cytosine in an Aerated Aqueous Solution, I

V. On oxalurate of ammonia as a constituent of human urine

When ordinary healthy urine is passed through animal charcoal in the manner described in the preceding paper, several organic substances are separated and absorbed by the charcoal in addition to the fatty acid there referred to. The liquid obtained by treating the charcoal with boiling alcohol having been evaporated, the residue is treated with water, which leaves the fatty acid undissolved. The filtered liquid yields on evaporation a quantity of crystals, which, after being purified in the manner described by the author, are found to have the properties and composition of oxalurate of ammonia. The watery solution of the substance gives with acids a white crystalline precipitate of oxaluric acid; with nitrate of silver it produces a precipitate which dissolves without change in boiling water, the solution on cooling depositing white silky needles of oxalurate of silver. The lead compound produced by adding acetate of lead to the watery solution, forms well-defined prismatic crystals. With chloride of calcium the watery solution gives no precipitate, but on adding ammonia and boiling, there is an abundant precipitation of oxalate of lime. By treatment with strong acids the substance is decomposed, yielding oxalic acid and urea. Its composition was found to correspond with the formula C 6 H 7 N 3 O s , which is that of oxalurate of ammonia. The author’s experiments were not sufficiently numerous to decide the question whether this salt is a normal constituent of human urine or not. There is no doubt, however, that its presence, whether exceptional or not, affords an easy and satisfactory explanation of a phenomenon which has until now proved very puzzling, viz., the formation of oxalate of lime in urine long after its emission. It is doubtless owing to the decomposition of oxaluric acid, which takes up water and splits up into urea and oxalic acid; the latter then combines with lime, of which there is always a sufficient quantity present to saturate the acid. There can be little doubt also that oxaluric acid is derived in the animal frame, as in the laboratory, from uric acid, the oxidation of which is its only known source.