Sonolysis of water at 447 kHz causes a decrease in the pH. The products formed depend to some extent on the nature of the dissolved gases; products observed are hydrogen peroxide, nitrous and nitric acid. The yield of hydrogen peroxide follows the order O2 > air > Ar > N2. In the case of total acid (nitrous and nitric) the yield follows the order air >N2 > Ar > O2. Nitrogen fixation occurs in the presence of Ar and O2 because of the presence of small amounts of N2 either as an impurity in the dissolved gases, or as residual air in the incompletely degassed water.An attempt was made by using the Fricke dosimeter to obtain information on the relative chemical activity of cavitation.
Chemical reactions that occur in liquids subjected to ultrasonic irradiation (insonation) of sufficient intensity to induce cavitation, have been attributed (1) to a number of processes; the reactive species produced in water and aqueous solutions during cavitation are hydroxyl radicals (2), hydrated electrons (3), hydroperoxyl radicals (4), and hydrogen atoms (5). These species are also produced during the radiolysis of water and in this paper we show that the sonolysis of thymine may be correlated with its radiolytic degradation.The radiolysis of aqueous thymine solutions has been the subject of numerous investigations and studies by Teoule and co-workers (6-11) identified more than 26 products formed during 60Co-y irradiation. Hydroxyl radicals produced by ionizing radiation react with thymine to give 6-hydroxy-5,6-dihydro-5-thyml and 5-hydroxy-5,6-dihydro-6-thymyl radicals; hydrogen atoms (or e,,-+ H,O+) react with thymine to give (5-uracyl)methyl, 5,6-dihydro-5-thyml, and 5,6-dihydro-6-thyml radicals (1 1). These radicals react. very rapidly with dissolved oxygen (e.g. K(TOH + 0,) = 1.5 x lo9 M -,l S-l (12) to produce hydroperoxide radicals which are reduced to the hydroperoxyhydroxydihydro products ( Fig. 1) (5 and 6) and the hydroperoxide products (7, 5-hydroperoxy-5,6-dihydrothymine, cis-and trans-6-hydroperoxy-5,6-dihydrothy-'For a preliminary communication see ref. 27. mine). The peroxide products are relatively unstable (11) and decompose to give various alcohols (cis-and trans-9, 8, 5-hydroxy-5,6-dihydrothymine, cis-and trans-6-hydroxy-5,6-dihydrothymine). In addition, the hydroxyhydroperoxides decompose to give 5-hydroxy-5-methylbarbituric acid and N-formyl-N'-pyruvylurea and the remaining products result from decomposition of N-formyl-N'-pyruvylurea to give pyruvylurea, urea, and formylurea.El'piner (1) was the first to investigate the effect of ultrasound on purine and pyrimidine bases. He insonated (500 kHz) aqueous solutions of the bases at an intensity of 5 W cm-2 in the presence of various gases. In the U.V. spectra of the insonated bases, the absorption maxima were reduced and the minima shifted to longer wavelengths. Uracil was found to be the most sensitive, adenine and guanine less so. In a later study, El'piner and Sokol'skaya (13) insonated aqueous solutions of cytosine, uracil, thymine, and adenine and investigated the products of sonolysis chromatographically but no degradation products were identified. The reduction in intensity of the U.V. absorption band of the various purines and pyrimidines was attributed to ring cleavage (1). Since the effect was considerably reduced in the presence of gases other than oxygen, it was suggested that molecular oxygen played an important role and a smaller oxidative role was assigned to hydroxyl radicals.This study was undertaken to reinvestigate the sonolysis of aerated aqueous thymine solutions Can. J. Chem. Downloaded from www.nrcresearchpress.com by 34.210.69.67 on 05/11/18For personal use only.
Als Hauptprodukte der Sonolyse von Thymin (I) in lufthaltiger wäßriger Lösung wurden die Hydroxy‐Derivate (II) und (III) sowie Harnstoff (IV) identifiziert.
Als Hauptprodukte der Sonolyse von Thymin (I) in lufthaltiger wäßriger Lösung wurden die Hydroxy‐Derivate (II) und (III) sowie Harnstoff (IV) identifiziert.
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