A detailed study has beeu niadc of the transient species produced by the reaction of eG, H and OH radicals with acrylamide (m,) in aqueous solution at natural pH (-6) and at pH = 11, using the technique of pulse radiolysis. The intense transient absorption spectrum which was observed at natural pH has been assigned to the protonated monomer radical anion, -mlH, and the products Rm,., of the reaction of R (= H, OH) with monomer. Their decays are second order and values of the extinction coefficients and rate constants have been determined. The yields of -mlH and Rm-' as a function of [ml] have been obtained and are compared with other solute systems which scavenge ea< in spurs. Thin layer chromatography has been used to identify adipamide and propionamide as two of the seven products obtained from pulse-irradiated solutions of acrylamide and an estimate of the total product yield has been made on the basis of these results.At pH = 11 the transient absorption spectrum has been assigned to the monomer radical anion, * m i and Rml. ; the decay of the former was first order whereas that of Rml * was complex and occurred with the concomitant growth of a permanent species. The extinction coefficients and rate constants for the decay of 'mi and Rml* have been determined. The yields of -mi and Rm19 as a function of [m,] have been obtained and compared with the corresponding yields of -mlH and Rml* at natural pH. Absolute rate constants (M-' s-I) have been obtained for the reaction of acrylamide with H atoms, ( 1 . 8 1 0 . 2 ) ~ lo'', CO;., -4x lo7, and *mlH, ( 2 . 5 k 0 . 4 ) ~ lo5, for reaction of *mlH with Ag+, (1.1 f 0 . 4 ) ~ lo8, and for reaction of ea& with propionamide, (3.0f0.5) x lo7, a-chloropropionamide, (5.8f0.5) x lo9, and P-chloropropionamide, (1.8f0.2) x lo9.E.s.r. spectra in a-methyl tetrahydrofuran glass at 77°K have been obtained for the radicals eH2CH2CONH2, CH36HCONH2 and the electron adduct of acrylamide. The yield and decay data presented in a previous publication ' for pulse radiolysed aqueous solutions of methacrylamide, N-t-butylacrylamide, acrylonitrile and acrylic acid have been recalculated in view of the yield dependence of (Gc);Y:H and (Gc)fG1. observed for acrylamide.
Pulse radiolysis of (a) aqueous de-aerated solutions of acrylamide, methacrylamide, N-t-butyl acrylamide, acrylic acid and acrylonitrile and (b) styrene and a-methyl styrene in de-aerated cyclohexane, dioxane, tetrahydrofuran and benzene results in intense transient absorption spectra. Those for system (a) are assigned to monomer radical anions, m f 0 , and the products of reaction of a radical with the monomer. Their decay is second order and values of the extinction coefficients and bimolecular rate constants have been determined. Absolute rate constants (M-1 sec-1) were obtained for the reaction of acrylamide with (a) hydrated electrons, (2.1 rt0.4) x 1010, (b) OH radicals, (2.0f0.5) x 109 and for the reaction of the product of the reaction of the radical and monomer with oxygen and ferricyanide ion, (1-9f0-3) x lo9 and (6-8f0-4) x 106 respectively. For system (6) the absorptions and decay kinetics observed are not completely understood. At least two distinct species are formed, one of which can be ascribed to a radical but neither to a radical anion. EXPERIMENTALThe pulse-radiolysis method has been '-' Consequently, only an outline of the equipment relevant to our work is presented here.PULSE IRRADIATION : A 2.5-3.0 MeV electron beam from a Van de Graaff accelerator was used throughout. The pulse duration ranged from 0-6 to 2-3 p e c and was generally used with currents in the range 100-300 mA per pulse. A 0.6 p e c pulse at 100 mA delivered a dose of approximately 2 3 krad. IRRADIATION CELLS : The rectangular irradiation cells were constructed of 1 mm thick Suprasil quartz with optically plane windows of Spectrosil A quartz. Internal path lengths for the light and electron beams were 1.0 and 0.7 cm respectively. The cell was filled and
An Inexpensive Flash Photolysis Apparatus and Demonstration ExperimentThe technique of flash photolysis is described in most high school and university undergraduate courses on physical chemistry but students seldom have the opportunity of observing and analyzing the data from a live experiment.
In the 120 krad/h, 60Co-γ radiolysis of air-free, anhydrous solutions of ferric hexafluoroacetylacetonate (Fe(HFA)3) in toluene at 27 °C, G(—Fe(HFA)3) = G(Fe(HFA)2) = 1.05 ± 0.03 molecules/100 eV and G(HHFA) = 0 where Fe(HFA)2 is radiolytically inert ferrous hexafluoroacetylacetonate and HHFA is hexafluoroacetylacetone. G(H2) = 0.13 ± 0.03 is not affected by Fe(HFA)3 while G(CH4)is reduced from 0.0088 &([a-z]+); 0.0020 to 0.0052 ± 0.0020 and [Formula: see text] is increased from 0.102 ± 0.019 to 0.307 ± 0.026 by Fe(HFA)3. Activation energies for the radiolytic formation of Fe(HFA)2, H2, CH4, and [Formula: see text] in the temperature range −95 to 27 °C, are 670 ± 130, 0, 1200 ± 900, and 1280 ± 25 cal mol−1, respectively.G(—Fe(HFA)3) = 1.05 represents the total yield of radicals scavenged since at the concentrations of solute used in the radiolyses the quantum yield for the disappearance of Fe(HFA)3 by reaction with solvent S1 and/or T1 states, generated by flash photolysis, is negligible [Formula: see text] Radicals trapped by Fe(HFA)3 are••CH3 (G ≈ 0.004) and unknown radicals (G ≈ 0.4) which are capable of combining with [Formula: see text] does not scavenge [Formula: see text] radicals (G ≈ 0.6). The formation of H2 in scavenger inaccessible spurs and CH4 and [Formula: see text] outside spurs has been confirmed.
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.
customersupport@researchsolutions.com
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.