The radiolysis of aqueous solutions of cyclopentane and cyclopentene containing 10"2 N2O or 10"3 M H+ has been studied in considerable detail using 14C radio-gas chromatographic methods. In the studies on cyclopentane the initial yields for production of cyclopentene and dicyclopentyl were found to be, respectively, 1.75 and 1.23 for acidic solutions (where eaq" is converted to H) and 1.95 and 1.36 for those containing N2O (where eaq" is converted to OH). The yields for attack on cyclopentane, 6.0 and 6.7, respectively, for the acidic and N2O containing solutions, agree quite well with the total yields of primary radicals (6.3 and 6.6) so that the material balance is excellent. From the relative yields the disproportionation to combination ratio for reaction between two cyclopentyl radicals in aqueous solution is 1.4 (±0.1). The studies on cyclopentene solutions give a similar ratio for reaction between cyclopentyl and cyclopentyl-2-ol radicals. The product distribution from cyclopentene solutions containing N2O indicates that 23% of the OH radicals attack cyclopentene by abstraction of an allylic H atom and pulse radiolytic studies give a value for this abstraction ~28%. Auxiliary studies on the rates of the radical reactions and on the esr and optical spectroscopic properties of the intermediate radicals are reported. The optical studies show that cyclopentyl radical absorbs only weakly with the absorption decreasing monotonically with increase in wavelength above 215 nm («215 ~1000 M"1 cm-\ esoo ~100 M~1 cm"1). Cyclopentenyl radical, however, exhibits an intense well-defined absorption band at 242 nm («242 2:8000 M~1 cm"1; width at half maximum = 20 nm). In the radiolysis of saturated aqueous solutions of cyclopentane (2.5 X 10"3 M) secondary reactions of H and OH with product cyclopentene become extremely important at doses >1018 eV/g (>3% conversion). For the acidic solutions the cyclopentene reaches a plateau of 3 X 10" 8 M, in accord with expectations from the measured disproportionation-to-combination ratio and the high selectivity (a factor -60) for addition of H to this product. For the N2O containing solutions the cyclopentene reaches a higher level (9 X 10" 5 M) because of the dominant importance of the less selective OH radicals. In general there is very good agreement between the experimental observations on the course of the radiolysis of cyclopentane and predictions based on the yields of radicals produced from the water and the relative rate constants for the different competing reactions which are known either from absolute rate measurements or from the studies on cyclopentene solutions.
Deoxygenated aqueous solutions of ethylene (4 x 1 0 -3 ~) and nitrous oxide (9 x 10-3M) were irradiated with y-60Co rays at dose rates of 2.6 x 1 015 and 2.1 x 1 Ofs eV g -l s-l. The most prominent among the 1 9 products determined are butane-l,4-diol, hexane-l,6-diol, and octane-l,8-diol. A satisfactory material balance with respect to primary water radicals was obtained. In the radiolysis of N,O-containing water the major part (ca. 90%) of the primary radicsls are OH radicals which are scavenged by ethylene to give (3-hydroxyethyl radicals. These radicals either combine, butane-1 ,$-dial being the product [reaction (i)], or add to ethylene [reaction (ii)]. The 2 H 0-C H2-C H , H 0-CH ,-( CH,),-C H 2 0 H 0) (ii) HO-CH,-CH, + CH,=CH, + HO-CH2-(CH2),-CH2 self-termination rate constant has been measured by pulse radiolysis [2k(i) = ( 5 f 2) x lo8 I mol-l s-l]. The propagation rate constant [k(ii) = (3 f 2) x lo4 I mot-l s-I] has been derived from the dose rate dependence of G(diols) by computer-aided fitting. The (3-hydroxyethyl radicals are readily oxidized by copper(!!) ions ( 5 x M). The major product is ethylene oxide [reaction (iii)], and little (ca. 3%) ethylene glycol is formed [reaction ( W I .
Thin layers of synthetic homopolypeptides (poly-α-Ala, -Arg, -Asn, -Asp, -Glu, -His, -Lys and -Tyr) and proteins (myoglobin, concanavalin A, trypsin-inhibitor) were irradiated under solid state conditions in an electron microscope with 100 keV electrons. Radiolytic changes were investigated by amino acid analysis. The results are discussed in terms of the relative radiosensitivities of the constituent amino acids, and possible topochemical effects on the sensitivity pattern emerging. An attempt is also made to trace at least some of the predominant pathways of amino acid transformation, namely the production of alanine and a-aminobutyric acid
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.